Archive #29 from Online Seminars for Municipal Arborists (on-line-seminars.com) November/December 2009
ISA will accept test scores for articles in this Archive.

List of Articles
Dealing with Drought
Genetic Code
Tree of the Seminar
Benefits of Mulch
Composting
Compost Tea
Tree Spec Liners
Tree Spec Planting
Research Briefs
The Monetary Value of Trees

Dealing with Drought
Mark W. Smith, ISA

Dry as a Bone!
That's a sentiment we've heard a lot down here in Central Texas as the drought of 2007-2009 drags on as one of the worst in Austin history. We're used to heat, and our trees are too, but temperatures exceeded 100 degrees (39°C) for 68 days this summer and August was the hottest month ever recorded in this area.

As an arborist, it should come as no surprise to you that droughts of this magnitude pose serious challenges for trees and for tree care professionals. The damage caused by droughts is difficult to quantify but, in the end, droughts cause millions of dollars worth of tree damage and they destroy the visual beauty of our natural landscape. With that said, it's important that we understand how to deal with droughts.

So what happens to a tree during a drought?
On the surface, trees appear to be pretty durable during a drought, but there's more going on than meets the eye. As soils dry out, feeder roots begin to die and their ability to absorb and transport nutrients is compromised. Then, as photosynthesis slows, the tree stops manufacturing food and begins to draw on stored energy. The leaves wilt, scorch, and begin to drop prematurely. As the tree canopy thins, cracks appear on the trunk and on branches, and suckers form at the base of the tree. Insects and diseases find the tree, now in a vulnerable state, an easy target, and their attacks speed up the decline. Unfortunately, many of these symptoms of drought go unnoticed until the following season, when staghorning appears, dead and weakened branches fall, pests and parasites get established, and a general decline becomes evident.

Preventing Drought Damage
As arborists, we can't prevent droughts but we can manage tree care to minimize the damage they cause. Regrettably, the approach I see all too often is to just not worry about it. There's a persistent myth that tree roots penetrate the soil so deeply that they find plentiful water even in times of drought. Not true! For most trees, the bulk of their roots are in the top 8"-18" (20-45 cm) of soil, making them very susceptible to changes in soil moisture. Consequently, most preventative measures are best focused in and around the root zone.

Let's take a look at some of the steps we can take to minimize drought damage:

Watering
Water is the most important component of any drought-survival plan. During droughts, water for personal use takes precedence over outdoor use, resulting in restrictions on outdoor watering. With less water to go around, it can be challenging to ensure that trees receive an adequate share under such conditions. Here are some steps to consider:

• Establish watering priorities as: 1) recently planted trees, 2) established trees, 3) lawns and shrubs.

• Adjust irrigation controllers to operate within restrictions and regulate water pressure to less than 100 pounds per square inch (7.03 kilograms per square centimeter) to avoid spray pattern distortion.

• Water before 7am or after 7pm to minimize evaporation.

• Slowly soak the root zone within the dripline to promote percolation and limit runoff.

• Apply supplemental water where necessary. Consider slow-release watering bags or watering trucks to get water to trees in isolated locations. The City of Austin routinely uses both of these resources for recently planted trees in our parks. Temporary bubblers or soaker hoses may also be useful if a water source is nearby.

• Consider alternative water sources: there are options to potable water. Many municipalities offer reclaimed water as an alternative to potable water. If this option is available to you, be sure to test the water to confirm that sodium levels are acceptable. Excessive total dissolved sodium is toxic to trees and can severely burn foliage and kill trees. Wells may be an option in some areas but, once again, we test subsurface water here in Texas for sodium and boron levels to confirm suitability for use. Surface ponds are useful as attractive site features and reservoirs to temporarily hold well water, potable water, or water pumped from creeks and lakes until used for irrigation. Underground tanks for rainwater harvesting are also a viable, although expensive, storage option.

Maintenance
Quality tree maintenance is an important on-going process that starts before droughts occur and continues well after they end. A maintenance program that includes regular monitoring, watering, mulching, pruning, and fertilization, maintains a tree's healthy vigor and best prepares it for drought.

• Prepare a tree care program and schedule maintenance to occur at regular intervals.

• Monitor weather and respond early to drought conditions.

Mulch
Organic mulch placed in the root zone provides numerous benefits for trees during droughts. Mulch retains soil moisture in the root zone, keeps roots cool, and controls weeds that might otherwise compete for water. As mulches decompose, they also add nutrients to the soil and improve its structure.

• Maintain a 3" - 4" (7.5-10 cm) layer of organic mulch within the dripline of existing trees.

• Mulch beyond the edge of the planting hole on newly planted trees.

• Keep mulch at least 3"- 4" (7.5-10 cm) away from the base of the trunk.

Pruning
Removing live branches and foliage to compensate for root loss, causes trees to expend energy at pruning cuts, and the loss of foliage reduces the tree's ability to grow when growing conditions return to normal.

• Avoid unnecessary pruning during droughts.

• Prune only to remove dead, broken, insect-infested, and diseased branches that may weaken the tree.

Fertilizers
Excessive soluble fertilizers in the root zone actually draw moisture out of the roots, resulting in fertilizer burn if adequate water is not made available. Fertilizers also encourage top growth and increase a tree's need for water at a time when little is available.

• Avoid applying fertilizers during droughts.

• Fertilizers, if used, should be in a slow-release form applied only at recommended rates.

Herbicides and Pesticides
Herbicides used in the lawn under a tree's dripline migrate down to tree roots and can be harmful to drought-stressed trees.

• Avoid heavy herbicide applications during droughts.

• Use pesticides to treat for infestations only as needed.

Summary
Until that wonderful day in the future when cloud seeding and other weather modification techniques bring us all the rain we need, droughts will just be something that we have to contend with. With a good understanding of how trees are affected by drought and how they react, we can be better prepared to promptly diagnose symptoms and develop effective tree care programs.

Mark Smith is an ISA-Certified Arborist, Landscape Architect, and Principal with RVi Planning + Landscape Architecture

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA science credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in. 

A Tree's Genetic Code
By Len Phillips

Trees are superior survival organisms. They live longer, grow taller, and become more massive than any other organism on earth. Throughout the planet, the goal of all living creatures is to survive and reproduce. The strategies to do so are programmed into a genetic code. In a tree, the genetic code is expressed as tree structure and function. Trees form bark, leaves, roots, and wood, and are able to respond to environmental stresses via the genetic code.

Survival of the Species
Trees survive and reproduce through the development of seeds. Trees also reproduce through regeneration from stump or root sprouts as well as by man-made propagation and cloning. Root sprouts occur when dormant buds that have formed during the growth of roots, begin to develop into sprouts as a response to injuries, disease, or other types of disturbance somewhere on the tree. (The details of this process have been explained in previous Seminar articles.) 

Tree Biology
Trees have survived for ages because their biology is involved and complicated. As Alex Shigo wrote, "Every living system will do something when its survival is threatened." Because trees cannot move away from potentially destructive agents and conditions, they have developed the capacity to adjust rapidly after being threatened by agents or conditions that could cause stress or death. The capacity to adjust is a genetic feature called vigor. A vigor code determines the effects upon a tree of such essential factors as space, water, elements, temperature, and soil pH. The vigor of an organism can only be measured when its life or its health is threatening in some way.

Trees of like species connect with one another. For example, pines, oaks, maples, and other species with air borne pollen spread the pollen around for other trees to use on their flowers. Trees also connect with other trees by way of root grafts as well as through the fungi that are associated with non-woody roots; these fungi are called mycorrhizae. Trees also connect with many other microorganisms in ways that benefit the trees and their survival. (More details of this process are available in the previously published Seminar article on mycorrhizae.)

Root Growth
Most tree species grow a taproot as a seedling for a certain distance or until an obstacle is encountered, and then the root system changes and continues to grow as a fibrous system. The root system must be in balance with the shoot system. The roots supply the shoots with sufficient moisture and nutrients, and the shoots must manufacture enough food to support the growth of roots.

Root cells develop in fixed positions to reach mature dimensions. Cells use water pressure to push against the walls and stretch the cellulose fibers as the cells elongate. This action forces the root tips through the soil against the mass of the tree. Roots are also sensitive to gravity and respond with gravitropism. (A great deal more on this topic can be found in the root physiology article that has appeared in a previous Seminar.)

Response to Soil Compaction
In response to increased compaction, roots thicken in diameter, root growth slows and more lateral roots are generated. Thicker roots exert more force and penetrate farther into compacted soil areas. If laterals are small enough to fit into the pore sizes of the compacted soil, lateral growth will continue while the main axis of the root is constrained. (More on this topic can be found in the soil compaction article that appeared in the last Seminar.)

Dealing with Stress
Trees are not free of disease or stress but have the capacity to resist the effects of both. Trees have developed complex biochemical processes that enable them to detect, respond to, and survive the many environmental stresses they encounter during their potentially long life spans. Various metabolites may detect early stages of stress before the appearance of symptoms such as reductions in woody growth, crown deterioration, or tree death.

Sometimes observant arborists will assist a tree's survival when they see possible signs of stress. For example, if a birch tree has become infested with borers, it sends up root sprouts. When the arborist destroys the insect, the sprouts often wither and die as the tree resumes normal growth. Arborists like to tell the story about the seedless honeylocust. When this tree unexpectedly develops seed pods, the arborist knows the tree is reacting to stress. Once the stress is removed, the tree reverts back to being seedless.

Compartmentalization
Unlike skin wounds, where human skin cells regenerate and heal tissue, trees "wall off" or "compartmentalize" their wounds. Compartmentalization resists the spread of infection and protects the vascular cambium by forming boundaries and barriers. By resisting the spread of infections, the boundaries protect and preserve the water, air, and mechanical-support systems of the tree. This minimizes the exposure of wood to the decay process and maximizes the volume of healthy sapwood for energy storage and active response to future injury and infection.

Just as trees develop highly compartmented systems that isolate decay, they also develop ways to survive after structural cracks are formed. Trees have the ability to alter cell forms in response to a lean in the stem that could lead to a fracture and trees can alter wood that forms around the margin of wounds. As trees sway, new tissues form in new positions that constantly adjust to potential weakness. When a radial crack does rupture the cambium, then woundwood formation starts and this adds strength to that portion of the trunk. (The details of this process have been explained in previous Seminar articles.)

Trees, like people, are each different in their individual healing schemes due to individual differences in health, cellular structure, and genetic makeup.

Tree Rings
Tree ring characteristics are a record of the tree's life history including disturbance and environmental change. The tree ring record provides perhaps the only environmental record for forests, spanning time periods from individual years through centuries and beyond. Pollen deposits also help greatly, where they have been captured and preserved. The basic anatomy of tree rings (ring width, density, cell types and dimensions) records the allocation and timing of captured energy into wood production. The rings may also record the exposure of tree roots to the soil-chemical environment over time, subject to internal chemical processes.

Circulatory System
While humans have veins and arteries, trees have a vascular cambium that forms new xylem (which matures into wood) and new phloem (inner bark) that needs to expand outward. Water in trees flows from the roots to the leaves along the xylem cells. The xylem consists entirely of cells that are joined together in long hollow tubes. These cells transport fluids to all parts of the tree using capillary and/or osmotic pressure actions. In a similar manner, the phloem cells transport foods to places where the food is needed and to storage in the roots. (The details of this process have been explained in previous Seminar articles.)

Processing Food
Trees, being in a fixed location, must manufacture their food. Furthermore, every tree must be able to store adequate carbohydrates, not only to reproduce leaves, roots, and growth each year, but also to "hold in escrow" the energy needed to grow new leaves if they are killed by weather, pests, or climate.

Trees must also have stored nutrients in early spring. By the end of spring, after a tremendous growth spurt, trees have used up a lot of these stored nutrients. A healthy tree will begin, through the process of photosynthesis, making and storing new supplies of nutrients (carbohydrates) for the following year. Trees utilize the elements in fertilizer, soil, and atmosphere to produce glucose, proteins, and other materials which might be considered food.

Urban Trees
Urban trees do not resemble a forest because trees are planted in isolation from each other, separated by barriers and sterile soils. Arborists can correct this by planting trees in groups and by eliminating root barriers between them. Then, with these connections, urban trees can reach their potential vitality.

Sources

• "Genetic Map Of Important Tree Genes Outlined", ScienceDaily, September 7, 2004.

• Gilman, Edward, "Dispelling Misperceptions About Trees" Publication #SSORH3, University of Florida Extension.

• Glickman, Joe, "Weekend Warrior", New York Times, July 2, 1999.

• Phillips, Jack, "Nature of Tree Care III", Tree Care Industry, January 2008.

• Pollan, Michael, "The Botany of Desire", Random House Inc. 2001.

• Smith, Kevin, Ph.D., "Are We Choosing Disposable Landscapes", TCI EXPO 2008.

• Smith, K. T., W. C. Shortle, R. Minocha, "Tree Biology and Mechanisms of Response to Disturbance and Changes in the Chemical Environment", Northeastern Research Station, USDA, September 2008.

• Shigo, Dr. Alex L., "A New Tree Biology Comes of Age", Tree Care Industry, Volume XI, Number 9, September 2000.

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA science credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

Tree of the Seminar
Edited by Len Phillips

Red Sunset^TM Red Maple is ideal for urban sites. It has good disease resistance, fast growth, and excellent year-round color. This information has been gathered from personal observations of the Editor, living in New England, Zone 5, and information provided by J. Frank Schmidt & Son.

Botanical Name: Acer rubrum 'Franksred'
Trade Name: Red Sunset^TM Red Maple
Parentage: Red maple selection by J. Frank Schmidt & Son in 1966
Family: Aceraceae
Year of Introduction: 1966
Height: 45' - 50'
Spread: 35' - 40'
Form: Oval upright crown
Bloom Period: Very early in the spring
Flower: Red, profuse, female only
Fruit: Winged, bright red samaras
Summer Foliage: Dark green and glossy in summer, leaves 2" x 4" wide
Autumn Foliage: Brilliant orange-red, persists until late autumn
Winter Color: Silvery color for winter interest
Bark: Silvery, thin bark, easily damaged
Habitat: Species native to entire east coast, west to the Mississippi River
Culture: Moist conditions, tolerates most soils, urban pollution and partial shade, requires acid soil
Hardiness Zone: 3 - 8
Growth Rate: Medium to fast, average of 2' per year
Pest Problems: Excellent pest resistance; some leaf scorch in warm climates
Storm Resistance: Good branch angles improve storm resistance
Salt Resistance: Susceptible to wind-driven road salt
Planting: Transplants easily; avoid fall planting in northern climates
Pruning: Seldom needs pruning because of strong wood
Propagating: Own root cuttings are best due to graft incompatibility
Design Uses: Excellent specimen for parks, lawns, and streets
Companions: Use with shrubs such as Taxus, evergreen Euonymus, and perennials
Other Comments: One of the best red maples, excellent in the Midwest
Available from: Most nurseries
Photos: J. Frank Schmidt & Son

To earn ISA-CEU’s for this article, click on TEST  for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA science credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

Benefits of Mulch
By Stenn Design

Mulch truly is worth its weight in gold if selected and used properly. Research has shown that an 8 foot (2.4m) circle of mulch properly applied under young trees can quadruple tree root densities when compared to young trees growing with turfgrass competition and no mulch. Likewise, in mature trees, mulching has been shown to increase fine root densities up to 15 times compared to trees growing with turfgrass competition and no mulch. Research has also shown that proper mulching can reduce soil pH and relieve leaf chlorosis (yellowing), increase soil moisture, increase mycorrhizal activity, improve soil structure and drainage, and reduce soil compaction levels over time (three to five years).

Benefits of Proper Mulching Over Time

• Mulch reduces soil moisture loss via evaporation.

• Mulch minimizes weed competition when applied more than 2 inches (5 cm) deep.

• Mulch moderates extremes in surface soil temperatures.

• Mulch improves plant growth and vigor.

• Mulch reduces soil compaction and erosion.

• Mulch improves soil aeration and soil structure.

• Mulch minimizes frost heaving of small transplants.

• Mulch may increase soil fertility.

• Mulch can reduce salt buildup.

• Mulch reduces reflection and re-radiation of heat.

• Mulch reduces the incidence of some diseases.

• Mulch is aesthetically attractive.

Application of Mulch
Selection and application of mulch should be based primarily on the mulch's effect on plant health, growth, and vigor rather than on aesthetics, cost, or availability. Improper mulch selection and application can cause detrimental effects on plant health and even legal liabilities for applicators. Too often, mulch is selected and applied purely from an architectural design standpoint and not from an understanding of tree morphology and biology. When selecting mulch, it is important to choose one that allows for the exchange of gases between the soil and air and the penetration of water down to the roots. Although some mulches may allow for a more gradual and controlled release of nutrients and energy for decomposing microbes, there is the potential to compact and become hydrophobic (water-repelling). These hydrophobic layers must be broken up before water will penetrate down to the soil and roots.

Mulching can be one of the best or one of the worst cultural practices that can be done for landscape plantings, depending on what is applied and how. When applied too deeply [4 to 6 inches (10-18 cm) or more] and particularly if prepared from fresh woody materials, mulch may undergo high-temperature decomposition in the summer. The result is that the mulch dries out to less than 34% moisture content on a total weight basis and becomes a dusty mass. Fungi may then completely colonize this dry mulch until it becomes a hydrophobic, compacted layer of mycelium. Usually, a light raking of the existing mulch is all that is needed to break up any crusted or compacted mulch layers that have become hydrophobic.

In addition, the use of mulch can have either beneficial or negative effects on the population of mycorrhizae. A shallow, 2 inch (5 cm) layer of wood chips or compost has been shown to improve tree establishment because mycorrhizae are stimulated by the slow-release sources of carbon and nitrogen in the organic matter. A deep layer (5 to 6 inches) of the same mulch has been shown to inhibit the development of beneficial mycorrhizae during reforestation efforts. Negative effects on mycorrhizae should be avoided because they are important to the overall maintenance of healthy plants.

Knowing the species and cultivars of plants in the landscape, their moisture requirements, and the soil's drainage is important in deciding which type of mulch to use. Studies have shown that soil moisture is conserved by using mulches because mulch obstructs solar radiation, reduces soil temperature, and obstructs evaporation, especially when the surface soil is near field capacity. In situations where shallow-rooted species are growing in poorly drained soils or clays, mulch depths rarely should exceed 2 to 3 inches (5-8 cm); otherwise, excess moisture may result in root stress.

For perpetually wet soils that need as much soil oxygen as possible for root respiration, using a combination of systemic post-emergent and pre-emergent herbicides may be more advisable than using mulch to control weeds. This practice allows proper surface soil aeration and gas exchange. Additionally, periodic soil drying improves soil structure and subsequent drainage. This weed control technique may be especially beneficial if plants requiring well-drained soils are planted on poorly drained soils. Be careful, however, to avoid spray application on desirable trees, shrubs, and flowers, especially when drift from wind may be a problem. Always follow the herbicide label recommendations and make sure the herbicides are applied by a trained and licensed applicator.

When mulching plants growing on well-drained loams or sandy soils, a 3 to 4 inch (8-10 cm) mulch depth is usually recommended. With coarse-textured mulches (large bark nuggets, for example), more can be applied because of the better oxygen diffusion through the mulch and into the soil. It is prudent to be more cautious with the fine-textured, more compactable, double-shredded mulches on the market.

Many landscape practitioners over-apply mulch using the excuse that it eventually will decompose. This is true, but decomposition rates of mulch depend on many factors, including type and particle size of mulch, the degree to which the mulch is already decomposed or composted, temperature, and moisture content of the mulch. Unfortunately, many practitioners apply excessive amounts of mulch every year because they think the decomposition rates will exceed their application rates. Excessively thick applications of mulch or mulch piled high against the trunks and stems of trees and shrubs continues to be a problem because many green-industry practitioners and the public are unaware of the potential stresses caused by improper mulching. A good rule of thumb is to keep mulch a minimum of 3 to 6 inches away from the trunks of young trees and shrubs and 8 to 12 inches (20-30 cm) away from mature tree trunks.

Over-mulching
Over-mulching continues to be a major problem. Conducting a visual inspection of the root flare is the best way for an arborist to check a tree or shrub for a possible root collar disorder caused from soil or mulch being piled against it. If no root flare or buttress roots can be seen, chances are good that at least some of the root crown has been buried. When burial is suspected, the arborist must first carefully probe downward to determine the extent and depth of burial. Soil or mulch must be removed to expose the root collar, allow the collar to dry out, and allow essential oxygen and carbon dioxide gas exchange.

According to Bartlett Tree Expert scientists, an amazing number of plants have improved rapidly in color and vigor within months of a root collar excavation. Observations also indicate far less winter injury in such plants because, following excavation, the healthy roots produce the growth regulators responsible for above-ground winter hardiness.

Over-mulching and root collar burial needlessly stress many landscape trees and shrubs. A summary of the potential problems associated with poor mulching practices include:

• oxygen starvation of the roots,

• lack of gas exchange,

• death of inner bark (phloem),

• promotion of stem and root diseases,

• prevention of winter "hardening off" via increased mulch temperatures and declining root vigor,

• rodent girdling,

• development of water-repelling mulch layers,

• potential short-term nitrogen deficiencies,

• nutrient and acidity problems from "sour" mulch.

Fortunately, most of the problems associated with mulches can easily be avoided and minimized with periodic inspections and timely education of the public.

Mulching Recommendations

• Determine the existing mulch depth before applying any additional mulch. Rake existing mulch thoroughly to enhance aesthetics and break up any underlying hydrophobic layers to allow water to reach the roots, particularly if the tree or shrub is on a mound or slope. Raking also breaks up slime mold "spore mats" and other nuisance fungi by promoting mulch drying. Slime molds are primarily an aesthetic eyesore and are not known to be harmful to trees and shrubs. Another option is to spade or rake the mulch into the soil surface layer and then soak it with water. The water is necessary to allow bacteria and fungi to colonize the mulch and organic matter. If fresh, dry mulch is placed on top of mulch colonized by nuisance fungi, the problems may occur again the following year or sooner. If artillery or shotgun fungus is causing a problem, either remove the existing wood-based mulch or cover it with some type of weed barrier or decorative mulch that blocks light and prevents the tar-like spore masses from sticking to houses, cars, and other objects. Researchers continue to study this fungal problem in hopes of finding a wood or bark mulch that will not allow the artillery fungus to sporulate.

• Use composted mulches. Fresh mulch usually is not a problem for mature trees but can be detrimental to other herbaceous plants. Hardwood bark mulch should be composted for at least three months if additional nitrogen is not added or at least one month if adequate nitrogen is added (1 pound urea per cubic yard) (0.48 kg per 0.75 cubic m) during proper composting.

• For well-drained soils with at least a 1 to 2 inch (2.5 - 5 cm) water percolation rate per hour, apply a 2 to 4 inch (5 - 10 cm) , mixed-particle-size mulch layer [2 inch depth (5 cm) for fine mulch and 3 to 4 inch (7.5 - 10 cm) depth for coarse-textured mulches].

• For poorly drained soils such as clays, a 2-inch (5 cm) mulch depth may be applied (just enough to give adequate weed control).

• On very poorly drained soils, applying combination herbicides containing a pre-emergent and a post-emergent herbicide may control weeds best and still allow for soil drying and aeration required for smaller, non-woody, absorbing roots.

• Conduct periodic soil testing, including pH tests, to ensure optimal mineral availability and ideal pH for adequate organic-matter decomposition and mineral release.

• Avoid "sour" mulches (smelling like ammonia) that have not been adequately aerated and composted. Sour-smelling wood chips have been known to kill herbaceous plants because of acetic acid and other toxic compounds produced from anaerobic decomposition.

• Avoid incorporating green or non-decomposed mulch (such as that from wood pallets or other wood products) into the soil. Such mulches have a high carbon to nitrogen ratio and will deplete soil nitrogen sources.

• If the trunk flare is buried or excessively mulched, remove the excess soil or mulch to expose the trunk flare and allow adequate drying, and replace soil with a coarse aggregate (but not a high-pH limestone).

• Check for automated irrigation systems, and position irrigation sprinkler heads so that water doesn't continually contact and saturate the tree trunk and trunk flare phloem tissue, which must be able to freely exchange gases.

• Mulch out to the tree's drip line (outer branch tips) if possible, adding only enough mulch every two to three years to maintain the desired 3 to 4 inch (7.5 - 10 cm) depth and only after existing mulch depth has been determined. When planting young trees and shrubs, extend mulch to 12 inches (30 cm) beyond the root ball, and enlarge the radius of mulch each year.

• Trees naturally create their own mulch each year by dropping, leaves, twigs, flowers, and fruit. This mulch smothers grass and weeds, moderates soil temperatures, and conserves moisture needed during environmental stresses. Mother Nature applies these mulches in thin layers that extend to the drip line of the tree or beyond.

Arborists who understand these natural processes and mimic them are less likely to make mistakes that cause undesirable consequences for trees. Although organic mulches need periodic replacement and maintenance to keep them looking attractive, when properly applied, their many functional benefits make them one of the most economical and beneficial cultural practices known to enhance tree health and vigor.

Online Seminars Survey
According to a recent survey conducted by Online Seminars, the message is getting out there to the professionals - keep mulch depths between 2 - 4 inches (5 - 10 cm), depending on mulch material, soil, and plant conditions as indicated in this article. The message is also getting out that the larger the mulch circle around trees, the better. The vast majority (78%) of respondents indicated they spread mulch beyond the rootball diameter. Twenty two percent indicated they add mulch to the diameter of the root ball, 36% will add mulch up to eight feet away, and 42% will spread mulch to the limits of the area loosened during the planting process.

William 'Bill' Harrington, the City Arborist for Medford, OR provided a typical response: "I like 2" to 3" of mulch although it is also somewhat dependent on the mulch material.  I mulch at minimum the rootball diameter but often extend it to the area of loosened soil.  It also depends on the site. For park trees I typically go with an over-sized area to keep mowers and pedestrian traffic back; in parkway or R.O.W. strips it is usually a more uniform rectangle."

Source
Stenn Design, "Woody Mulch Research Review, Professional Users and Product Availability Surveys", Seattle Public Utilities, December 2004

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA practice credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

Composting
Edited by Len Phillips

 

The making of compost is a simple process, but a thorough knowledge of the process is required in order to insure success. Healthy compost provides all the organisms and nutrients required by a tree, and in the proper forms for a tree to use. Healthy compost holds nutrients in non-leachable forms so they remain in the soil until the tree requires the nutrients.

Composts are made by thermal composting (described below for municipal and commercial operations), by worm-driven processes (cold-composting for homeowners and small operations), forest composting, or by static composting (anaerobic composting which takes years to accomplish).

Composts that are stable and possess significant amounts of humic acids have the ability to bind nutrients and heavy metals as moisture passes thought the product layer. Compost also improves the cation exchange capacity of the soil, increasing sites in which nutrients can be bound, and provides a home for microorganisms to proliferate. Some organisms that live in compost have the ability to degrade organic contaminations such as hydrocarbons.

Thermal Composting
A successful municipal or commercial composting operation requires careful planning and attention to:

• site selection,

• the collection system,

• the management of the materials,

• utilization of the product,

• community involvement and support.

Selection of the composting site is frequently a political decision and one that often generates neighborhood opposition. This opposition comes from a lack of understanding about how the composting process works. One often-used argument deals with leachate from the compost. However, leaves, grass clippings, and wood chips or wood debris do not create leachate problems. Animal manure wastes, while providing nutrients to the compost, could cause leachate problems. Another complaint deals with odor. However, since a properly managed leaf-composting operation generates few unpleasant odors, there is little reason for complaint.

The composting site can be any former landfill, unused park, or vacant land. The site must have a total acreage that will equal approximately one acre of compost site per square mile of municipality, or 1 acre per 30 miles of streets, whichever is less. It is more efficient to conduct the entire operation at one site, but in larger cities this is not always feasible. If residents are expected to deliver products to the site themselves, the site needs to be accessible to most everyone in the municipality, but if the municipality picks up organic material citywide, then access is less important. The site should be gently sloping, well drained, and hard, and open so there is room to maneuver equipment as well as store the products. Surface drainage should not go directly into brooks or catch basins.

Since leaves are usually the biggest concern with organic material composting, the following process should begin in the fall. The leaves should be piled in windrows that are as long or as wide as the available site and as high as the equipment (loaders) can reach for maintaining the piles. The piles should be as wide as they are high and should run up and down the slope so the piles do not trap rainwater. The windrows are designed to let air and moisture enter the piles. Many operations find it advantageous to build twin windrows when the leaves are being delivered to the site. At the first turning of the piles, the two rows are combined into one. Since the most rapid amount of leaf size reduction occurs in the first month, the twin piles can easily be managed as one large pile after that first month. As a general rule of thumb, 1000 cubic yards (800 cubic m) of leaves on the street will eventually become about 200 cubic yards (150 cubic m) of composted leaf mold.

Size reduction can also be accomplished by mechanically shredding the leaves prior to composting. Shredding will reduce the amount of time necessary to complete the composting process by almost 50%. Uncomposted shredded leaves can also be used as mulch in gardens or around trees. However, since the leaves decompose very quickly, they have to be replaced annually. Leaves can also be blown away if the landscaped area is windy.

The decomposition process has been rumored to rob the soil and trees of nutrients, and it does use nutrients in the very short term. But these nutrients are returned very quickly to the soil; when the decomposition process has finished, all the nutrients are once again available to the tree. Furthermore, if the compost or organic matter is applied to the surface, then the nutrients, mostly nitrogen, are used just at the surface, and that does not rob the root area in any significant way.

Ingredients and Procedures:
The following provide all the necessary steps required to insure successful municipal or commercial composting:

• Air - Ideally, perforated pipes should be run through the compost pile. A more practical solution is to loosely stack the leaves in long, narrow rows using a front-end loader. Oxygen is essential for preventing anaerobic decomposition while promoting aerobic composting with a minor, but not unpleasant, odor.

• Turning - Turning the pile mixes the materials, re-aerates the compost, and provides a check on the progress of composting. Turning also speeds the composting. The minimum interval is four days; the more practical is one month. The more you turn the pile, the more the compost tends to become bacterial, because any kind of disturbance destroys fungi by breaking up their mycelia. The top 2 feet (0.6 m) of surface area are unlikely to decompose as readily as the interior of the pile. Therefore, when turning the pile, exteriors should be moved to the center of the new pile and the centers moved out to cure at the edge.

• Nutrients - Nitrogen is very important for feeding the composting bacteria. The best source would be to add manure to the compost during the turning procedure. If manure is not available or not allowed, the next best sources of nitrogen are weeds, grass clippings, aquatic weeds, and commercial nitrogen fertilizer. All but the fertilizer also supply the heat required for composting.

• Bacteria - Commercial bacterial compost starters are available; however, the occasional mixing of compost with previously composted soil should provide sufficient quantities of bacteria seed. If the same site is used year after year, the bacteria can be obtained by scrapping up the top inch or two of soil when making the windrows for the first time. After the composting action has begun, additional bacteria do not need to be added.

• Heat - The optimum temperature is 140°F (60°C). This is not difficult to obtain in summer but composting over winter requires special insulation with hay or uncomposted leaves, which will also protect the pile from winter rains. When the internal temperature of the pile or row has cooled to 100°F (38°C), the compost action is finished. Weeds, green vegetation, and manure speed up the heating and composting action.

• Moisture - Rainfall is generally sufficient, but a sprinkler may be necessary to supplement natural rainfall and maintain the moisture content at a wet but not dripping condition.

Turning the pile on a rainy day allows moisture to be mixed throughout the entire pile. It also provides an opportunity to utilize equipment that would normally be working on other outdoor projects. If the piles are close to residential neighbors, rainy day turning takes advantage of the fact that neighbors' windows are likely to be closed because of the rain, reducing the likelihood of any complaints if odor is released.

As the composting action proceeds, the pH value fluctuates from acidic in the beginning to neutral at completion, regardless of the product being composted. When the compost cycle is completed, the row may be screened to remove any uncomposted leaves, sticks, etc. The material is then piled to cure. Curing allows the compost to stabilize so nutrients are released when applied to the landscape instead of being consumed by bacteria and continued decomposition.

Uses
Uses of composted leaf mold are many:

• It can be mixed in equal parts with sand and soil to create topsoil.

• It can be substituted for peat anytime peat is required in construction or for greenhouse potting soil.

• It makes an excellent top dressing for turf areas and mulch in a garden.

• It is an excellent cover for construction restoration.

Many communities and commercial operations sell the material to topsoil contractors, greenhouses, nurseries, garden shops, and residents. Other communities with successful composting operations no longer purchase topsoil . Some use the material as incentives for sales of other surplus products such as woodchips and lumber from forestry operations. For example, buy a bag of cedar wood chips and get a bag of compost free. Some communities have a Give-Away Day to get rid of their surplus leaf mold. Other communities sell it for $25 - $45 per yard, screened and delivered.

Worm-driven Composting
Many communities actively encourage residents to develop backyard or worm-driven composting areas to eliminate leaves and grass from ever getting into the municipal waste stream. There are many residential programs and methods of composting available. For example, a 14-day compost is good for small amounts of residential yard waste material. This is accomplished with a rotating barrel that contains fresh green grasses or leaf clippings and is rotated every two or three days.

Many residents have compost piles in their yards. Compost piles can be filled with any biodegradable, non-animal waste product. Compost bins are best made with wire sides and in three sections so the compost can be moved from one bin to the next as the compost decomposes. Wood posts and beam designs are also quite popular as are plastic containers designed to be used as compostors.

The "lasagna method" of composting, where layers are built up in the garden, is a favorite of many gardeners. A four inch layer of leaves, grass clippings, or other compost material is spread over an area. This is then covered with a half inch of soil. Then another layer of leaves or other compost product is placed on top of the loam, and the layering process is repeated several times. Once this is completed, trees, plants, or seeds can be grown in the top layer, which should be loam. Keep the pile moist but not wet and do not turn the pile until the following spring. Sides to the compost pile are optional, depending upon the number of layers and total height.

The trench method is another homeowner approach. Begin by digging a long, open trench in the garden. The compost products are placed in the trench and then covered with soil from a second trench dug right beside the first. The second trench will be left open until new compost products become available and the trenching process continues. Dig the trenches a shovel blade deep. If trimming trees and shrubs, go deeper so the branches and twigs are completely buried. Some people suggest digging the second year's trenches at right angles from the previous year's trenching, so that all the soil will be eventually turned over.

In an average suburban garden, during the course of the summer enough compost material will be generated to cover an area that is 8 feet (2.4 m) wide and 25 feet (15 m) long. In the fall, repeat the process again with leaves. This process takes a lot of effort but it works. In a 15-year period, up to 1 foot (30 cm) of rich black, well-drained loam can be produced.

Compost develops good soil structure by binding pieces of soil together and by building airways and passageways through the soil. Good movement of air and water are vital to the health of trees and the soil/food web itself. While it may seem contradictory, good soil structure allows water to drain from very wet soil, but it also helps the soil to hold water when soils start to dry out.

Forest Composting
This process is the natural composting process, usually found on the forest floor. It is also used by organic gardeners who practice no-till gardening. Organic matter breaks down from the surface downward. Different groups of organisms provide different functions. For example, leaves on the surface are attacked mainly by fungi in the first step, and then other organisms continue the process. Every year a one-inch layer of organic material is added to the surface and allowed to decompose naturally. This practice cannot be used if earthworms are present in the soil, since they decompose the material too quickly.

Static Composting
By contrast, static composting is done by making a pile of leaves and letting them decompose without any management. This requires 2 to 3 years, and the anaerobic decomposition that results may produce odor and alcohol problems.

Compost Types
Composts can be dominated by either bacteria or by fungi. Bacteria-dominated compost is best applied to herbaceous plants and trees. For the bacteria to dominate, compost should be made from green materials such as 25% high nitrogen ingredients, 45% green plants, and 30% woody material. High nitrogen materials include manure, grass clippings, and legumes such as alfalfa, peas, clover, and bean plant residues. Green material includes any green plant debris, kitchen scraps, and coffee grounds, which all contain sugars and proteins that bacteria love. Woody material includes wood chips, sawdust, and paper products. The more frequently you turn the pile, the more the compost tends to become bacterial.

Fungi-dominated compost is good for mulching and for woody plant growth. Fungal compost consists of approximately 25% animal manure, 50% green plant material, and 25% shredded wood plant material. Any kind of disturbance to the compost pile destroys fungi by breaking up the mycelia. Fungal compost is especially useful for suppressing disease and introducing fungi for root development immediately after tree planting.

Sources

• Goldstein, Jerome, "Leaf Composting Installations", Compost Science/Land Utilization, Sept/Oct 1980.

• Haynes, John F. and David Harlan Cade, "Alternative EC", Landscape Architect and Specifier News, November 1999.

• Martens, Mary-Howell R., "Just What the Doctor Ordered", Acres USA, February 2001.

• Personal communication from Butch Ragland. If you want additional information about compost and soil organisms that create "aggregates of soil", see http://www.bloomingtononline.net/forum/forumdisplay.php?f=148

• Soil Foodweb Inc., website, 2009. http://www.soilfoodweb.com/03_about_us/approach_pgs/b_01_compost_information.html

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA practice credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

Compost Tea
Edited by Len Phillips

When compost tea is sprayed on a tree, the tree will often grow more vigorously, resist disease and insect attacks, and may produce higher yields of flowers and fruit. While chemical pesticides work by killing microorganisms, both the pathogenic and the beneficial ones, compost tea works on a very different principle. Inoculation of the soil with beneficial organisms can help release plant-available nutrients, aid the decomposition and recycling of soil organic matter, improve soil structure, and add beneficial organisms to the soil. Soil is full of microorganisms such as bacteria, fungi, protozoa, and nematodes that can aid tree growth. Soil also contains disease-causing bacteria, fungi, protozoa, and root-feeding nematodes. The goal for using compost tea is to enhance the beneficial microorganisms in the soil.

Harmful bacterial decomposers and the tree-toxic products they make are enhanced by anaerobic or reduced oxygen conditions. By making sure the tea and compost are well oxygenated and highly aerobic you eliminate 75% of the potential tree-disease-causing bacteria and tree-toxic products. To take care of the other 25% of the potential diseases and pests, get good microorganisms into the soil as well as on at least 60% - 70% of the trees' leaf surface. Good bacteria work against the detrimental ones in four ways: they consume the bad bacteria, the good bacteria may produce antibiotics that inhibit the bad bacteria, the good bacteria compete for nutrients, and the good bacteria compete for space.

Making Good Compost Tea
To make good compost tea, start with actively managed, mature compost that has been turned a few times and allowed to heat adequately to kill weed seeds and pathogens. Worm compost also makes excellent tea without the hassle of turning or checking the temperature. Add to the finished compost a little forest-floor debris. Then fill a 5 gallon (20 l.) plastic bucket half full of the compost. Metal containers are not recommended because the compost tea can corrode certain types of metal. Compost tea should not be made from manure-based compost unless the pile temperature exceeds 135ºF (57ºC) for at least 10 to 14 days and the compost is carefully made to ensure uniform heating. Deadly pathogenic bacteria are killed at this temperature.

Tea Bag
Next, transfer the compost into a "tea bag" made from an old nylon stocking, pillowcase, plastic mesh feedbag, nylon window screening, or burlap. It is important to use a clean material for the tea bag - one that has not been treated with any chemicals. The mesh size of the tea bag will determine what components are extracted into the water. With a fine mesh bag, only the tiny, soluble components will enter the water. This is important if the compost tea will be applied with a sprayer or in an irrigation system.

Tea Water
The bag is then suspended in the 5-gallon (20 l.) bucket, half full of water. Fill the bucket to within 3 inches (7.5 cm) of the rim with water. It is important to use water that is as pure and as uncontaminated as possible, such as rainwater, well water, or well aerated tap water. Water containing high levels of salts, heavy metals, nitrates, pesticides, chlorine, or pathogens, should not be used because they will affect the survival of beneficial organisms in the compost and may also affect the trees on which the compost tea is applied.

Aeration System
If the tea is not aerated constantly, the organisms in it will quickly use up the oxygen and the tea will start to stink and become anaerobic. An aquarium aerator can be used to add sufficient air to the water. Cut a length of plastic tubing that comes with the aerator pump kit and attach one end to the pump and the other to a gang valve. Cut three more lengths of tubing long enough to reach comfortably from the rim to the bottom of the bucket. Connect each one to a port on the gang valve and push an aeration bubbler on the other end. Hang the gang valve on the lip of the bucket and bury the bubblers at the bottom, under the tea bag. It is important to choose a system that will provide the proper amount of water agitation and aeration. When compost tea is not adequately agitated, oxygen can become depleted, resulting in poor extraction of material from the compost.

With the bubblers working, add 1 oz. (30 gm) of organic, unsulfured molasses to the water and stir vigorously with a stick. The molasses feeds the bacteria and gets the beneficial species to flourish really well. After stirring, rearrange the bubblers so they are on the bottom and well spaced. Try to stir the tea at least a few times a day. A vigorous mixing with the stick shakes more organisms loose from the compost soil and into the tea.

There are more sophisticated compost tea micro-brewing systems on the market, and these are designed to optimize aeration and recirculation by swirling the water around the compost in a continuous vortex. The high-tech approach reduces the time required to produce a good quality, microbially diverse compost tea, and it is especially valuable in producing large quantities of compost tea commercially. Using a sophisticated micro-brewing system, it is possible to produce good-quality compost tea in 18 to 24 hours.

Brew Time
In general, it takes 3 days to make a batch of compost tea. The longer the compost remains suspended in the water, the greater the amount of soluble materials that will be extracted from the compost. These include both living organisms and the nutrients that will feed them. Compost tea that is well aerated and recirculated will require a shorter brewing time than tea made without adequate agitation. If you leave the tea steeping for more than 3 days, more molasses must be added or the good organisms become dormant because they don't have enough food to stay active.

Cleanup
Once a batch has been completed, every piece of equipment - tubing, bucket, teabag, etc. should be thoroughly cleaned. Remove all slime from the containers. Without a thorough cleaning the next batch could fail.

Environmental Conditions
Temperature and evaporation affect the quality of the compost tea. If the water is too cold, extraction will be reduced and microbe growth will be slower, but if it is too warm, microorganisms may be inhibited or excessive evaporation may occur. It is hard to change the weather, but a cover over the container in hot weather should help reduce evaporation.

Application
When the tea is ready, let the brew sit until the compost is pretty much settled out, which is usually 10 to 20 minutes. Then strain it into another bucket or directly into the sprayer. If desired, this is the time to add foliar micronutrients, like kelp, humic and/or fulvic acids, commercially available microbial spore suspension, or rock dust. These stimulatory additives can be included to improve the final quality of the compost tea. Once the aerators are shut off, use the tea within the hour if possible. The solids left over after the tea is finished can be returned to the compost pile or added to the soil.

Compost tea can be applied as a foliar spray. Spraying can be done as little as one time in the spring up to every two weeks during the growing season. For best results, at least 75% of the upper and lower leaf surfaces should be covered with each application, and the tea should be applied every two weeks throughout the growing season, beginning two weeks before bud break. The tea should be applied before 10:00 AM or after 3:00 PM on sunny days because UV light will kill the microorganisms.

As a soil drench, the tea should be applied at about 1 quart per plant. Start when the plants have developed their first set of true leaves.

Odor
With any form of compost, solid or tea, bad smell means bad product or anaerobic compost. Healthy, adequately-oxygenated compost and compost tea should smell sweet and earthy. Never use a smelly compost tea on your trees, because alcohol from the anaerobic decomposition will destroy cell walls and tree roots. If the compost tea smells bad, aerate it until the smell goes away.

Microorganism Selection
Just like compost, compost tea can be dominated by either bacteria or by fungi. Bacteria-dominated compost tea is used as a foliar spray applied to herbaceous plants. It is especially useful for preventing foliar diseases. For the bacteria to dominate, the tea should be made from a preponderance of high-nitrogen ingredients and green materials as noted in the previous article about "Compost". High-nitrogen materials include manure, grass clippings, and legumes such as alfalfa, peas, clover, and bean plant residues. Green material includes any green plant debris, kitchen scraps, and coffee grounds, which all contain sugars and proteins that bacteria love.

Fungi-dominated compost tea is good for spraying around berries, fruits, and trees. Fungal compost consists of animal manure, green plant material, and shredded wood material. Woody material includes wood chips, sawdust, and paper products. Fungal compost is especially useful for suppressing disease and introducing beneficial fungi for root development immediately after tree planting.

If worm compost (vermicompost) is used, the material does not have to reach the same temperatures but must be adequately processed by the worms. Passage through the earthworm digestive system kills human pathogens and most tree pathogens, but adequate time must be allowed for worms to process all the starting materials.

Sources

• Ingham, Elaine R., "Brewing Compost Tea", Kitchen Gardener - October/November 2000, No. 29.

• Martens, Mary-Howell R., "Just What the Doctor Ordered", Acres USA, February 2001.

• Soil Foodweb Inc. website, 2009. http://www.soilfoodweb.com/03_about_us/approach.html

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA practice credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

Northern Illinois Tree Specification – Liners
Edited by Len Phillips

Changes in production techniques have resulted in trees that frequently fail to meet expectations for healthy growth and adaptability. Many of our expectations are based on trees growing on native natural soils, not our typical unnatural, urban sites.

To reverse this trend, segments of the green industry in northern Illinois got together to draft landscape specifications about how to propagate, grow, install, and maintain planted trees within limited budgets and short construction deadlines. This group of individuals formed a working group called The Northern Illinois Specification Review Committee. The members of the group represent growers, contractors, landscape architects, and urban foresters. This group has been meeting to discuss numerous concerns raised about the lack of specific standards for use by professionals when specifying, growing, digging, transporting and planting trees in northern Illinois. Based on their discussions, they developed a set of guidelines for use in northern Illinois. However, the results should be helpful everywhere.

Impact of Liner Planting Practices on the Finished Tree
Every phase of production and handling of nursery trees must be done well to have high quality trees to plant in the landscape. Since the majority of landscape trees purchased from local nurseries in Illinois and the Midwest are planted as liners, there is no substitute for obtaining quality liners and planting them correctly in the nursery to grow quality trees.

Grading
Grading is the process used to determine the quality of the liners. Sometimes grading occurs in the field, but most often grading occurs after the liners are harvested.
Bare root shade tree liners should be graded for size (caliper and/or height) as well as overall quality of the roots, trunks, and tops.
Liners should have several lateral roots spaced evenly around the trunk to provide support so the trees do not blow over in the wind.
Liners should have as many small roots as possible. These roots are key to the uptake of sufficient water and nutrients. Fibrous roots can be achieved by root-pruning and under-cutting or transplanting at any stage of production. Often, root-pruning is done on bare root liners by pruning the ends off of the roots prior to planting.

Liner Root Problems
"J" roots are most often the result of how the liners were planted in the field. They can be caused by a mechanical planter or wet field conditions when all or most of the roots, including the structural roots are dragged to one side of the planting trench. The resulting root structure is shaped like a "J". "J" roots may not provide enough support or stability.

Two-sided root systems are most often the result of liners that were planted too close together, or liners that were left on the same spacing for too long before being transplanted. The tops of these liners also tend to be two-sided or flat.

Circling roots are roots that grow in a circle around the trunk or around other roots. They are often the result of liners that were at one time grown in a plug or container. Circling roots may eventually kill the tree.

Torn or broken roots are often caused by the digging machine used to harvest the liners. Prior to planting, these roots need to be pruned back to the point at which they were torn or broken. The larger the damaged root, the greater the potential for future problems. The liner may not be left with enough structural roots, or the tear may extend up the trunk causing damage to the root crown or root flair. These conditions require discarding the tree.

Trunk / Central Leader
The trunk should be as straight as possible. The cut made when re-growing the top should be just above the major structural roots. The "shank" that results from this procedure is then minimized, producing a straighter, better looking trunk. Additionally, having a shorter shank at a consistent height above the structural roots will help to ensure that the liners are consistently planted at the correct depth. The base of the trunk should not have a large pruning cut from re-growing the top. A large cut may not close quickly or properly and may provide an entry point for insects and disease.

The central leader should be alive. If topped, there should be no canker, insects or disease under the tape sometimes used to train the new leader.

The trunk should have no visible cankers and no major damage from poor pruning cuts or poor handling practices.

Branching
The branches should be evenly spaced around the trunk without excessive gaps between the whorls. This helps to ensure that the tree will have good branching on all sides. It also allows for flexibility in pruning to the desired clear trunk height. Ideally, there should be no branches with tight crotch angles. If there are, they should be pruned out to avoid multiple leaders.

Some liner producers differentiate between "branched" and "light branched" liners. Light branched liners are typically defined as having fewer and/or shorter branches, most often on one side only. They are sold as a more economical alternative.

Shipping Liners
When the liners are shipped, they are usually tied together in bundles. The bundles should be tied in such a way as to not make cut marks on the trunks or roots, or cause the trunks to be bowed. 

• The roots should be kept moist. They should not be allowed to dry out during grading or shipping, or prior to planting.

• The roots, trunks, and tops should be free of molds, insects, and diseases.

• The buds should be tight and not breaking.

• Harvesting correctly will assure that trees arriving on the landscape site can be planted without having to spend extra time correcting problems resulting from the production process.

Root Replacement
Natural lateral roots (structural roots) of seedlings are often replaced by adventitious structural roots regenerated at the cut end of the primary root after it is pruned during field nursery production. These adventitious structural roots have been referred to as the adventitious root flare. A root shank longer than a few inches will lead to deep planting which is not desirable. On some species, adventitious roots may be produced on the root shank after planting, but this is not common.

Planting high to compensate for a long root shank will raise the bud union higher above ground, which may be aesthetically undesirable. Sudden exposure of this root shank tissue to an above-ground environment it is not accustomed to could result in cold or sun injury in some species. When planting high, it may be best to cover the root shank with a mound of soil that can erode away gradually.

The bud union and/or cutoff wound should be seen above ground at the base of the trunk, at the same depth as when it was grafted. This is typically about 1-2 inches (2.5 - 5 cm) above the soil. The presence of this bud union or cutoff is a sign that the liner was planted correctly, not an indication of inferior quality.

In-Ground Planting Methods
Depending on the size of the liners, and the preferences of the nursery manager, field-grown and container-grown liners may be planted by machine or by hand. Trenches or holes are often dug by machine for hand planting.

Regardless of planting method, the roots should be located at the proper depth and spread evenly in all directions. Avoid creating circling, twisted, or "J" roots by dragging or twisting the liner while planting. Pulling the liner up to adjust height after backfilling can also distort the root system and force the roots into a vertical position.

Additional Information and photos
http://www.ina-online.org/treespecs2-06thumbnails.html

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA practice credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

Northern Illinois Tree Specification – Planting
Edited by Len Phillips

It takes only a short time to plant a tree, but how it is done can have a lasting influence. Mistakes made when planting tress are usually impossible to correct later. Shortcutting the planting process can cause the tree to die, or struggle for many years and never reach its full potential as a healthy vigorous addition to the landscape. Attention to detail at planting time will pay dividends for years.

Structural Root Location
As a general rule for young nursery-grown trees, there should be two or more structural roots within 1-3 inches (2.5 - 7.5 cm) of the soil surface. "First order lateral roots" is another term that has been used for these roots. The structural roots begin to form very early. On seedlings, they start as the natural lateral roots arising from the primary root just below the soil surface. On cutting and tissue-culture-propagated plants, the adventitious roots that form very early usually develop into the structural roots. Often these roots form only at the bottom end of the cutting. The size and number will vary with species. If the roots are deeper than 3 inches (7.5 cm), consider rejecting the stock, as the root ball may be undersized (See American Standard for Nursery Stock 2004 in a previous Seminar).

The best time to determine root depth is while tagging trees, before they are dug. It can also be done after the trees are dug. Checking in the nursery and rechecking just before planting may be the best way to be absolutely sure that the roots are not too deep in the root ball.

Checking for root depth can be done several ways. A gap between the base of the trunk and the soil is a sign that the roots are too deep. An inexpensive surveyor's chaining pin or a stiff piece of wire can be used to probe for roots in the field, or in the root ball. The severed ends of the structural roots can sometimes be seen poking through the burlap on the sides of the root ball. Carefully removing soil from around the base of the trunk with a hand trowel is also acceptable but difficult to do after the root ball has been wrapped in burlap and ropes.

Placement of Structural Roots in Relation to Grade
If structural roots are found at the correct depth, plant with the top of the root ball slightly above grade. If the structural roots are slightly deep in the root ball, plant with the top of the root ball higher above grade. Leave the soil in the ball above grade intact, at least until the root ball is placed in the planting hole and backfilled.

Sometimes it may be preferable to leave the extra soil above grade rather than remove it and risk cold or sunscald damage on the tender trunk surface. If the extra soil over the structural roots is filled with fibrous roots, removing them suddenly could cause extra stress. The extra soil should gradually erode away. Mulch can be used to cover the protruding root ball and make a more gradual slope.

Removing Non-Biodegradable Materials
Materials used to cover and support the root ball during transport and storage can injure trees if left in place after planting. If root ball has been reburlapped, burlap on the outside of the basket should be removed after the root ball is placed in planting hole.

Remove all basket wires down to 4-6 inches (10 - 15 cm) below the root ball shoulder to eliminate the wires most likely to make contact with the structural roots. After removal of basket-top horizontal ring(s) and loops, twine can be retied over the top of root ball to stabilize the trunk through the first year. Low-profile baskets are designed so that there is no wire that needs to be removed. It is not necessary to remove the loops, even if they are less than 4-6 inches below the root ball shoulder. Chances of roots growing through them are low.

If all burlap and twine are not removed from the top of the root ball and down the side to 4-6 inches (10 - 15 cm) below the shoulder at the time of planting, each root ball should be inspected within a year to confirm that the burlap and twine have rotted away and are not damaging the tree's root system.

Pruning
If pruning was done correctly during production in the nursery, the tree should require very little pruning when planting, except for removing broken twigs. It is best to not make large pruning wounds on the stem. Proper pruning cuts just outside the branch collar are imperative.

Planting Pit Depth and Width
The planting hole volume should be large enough for rapid initial root development during the first year and to encourage root spread beyond the planting hole.

The planting hole should be slightly shallower than the root ball depth to anticipate flattening of the root ball. A hole two inches high is adequate for a 2-3 inch (5 - 7.5 cm) caliper tree; up to 4 inches (10 cm) high may be needed for larger root balls. The root ball should be placed on stable subgrade to minimize settling.

On sites with poor quality, compacted, clayey, or poorly drained soil, the planting hole should be at least two times larger than the width of the root ball diameter. If the roots are unable to grow into the compacted subsoil, a hole with sloped sides will allow them to gradually grow back up toward the better quality surface soils and continue to spread beyond the planting hole. On sites with high quality soil, the planting hole needs to be only wide enough to facilitate planting.

If the sides of the hole are glazed or dried, use a hand tool to break up surfaces before planting.

It is not possible to dig a wide hole when installing trees with a tree spade. After planting, the soil around the root ball can be deeply cultivated to eliminate air pockets and provide a favorable environment for new root growth, similar to a wide planting hole.

Backfilling the Planting Hole
Compact some of the excavated soil around the base of the root ball to stabilize it. The rest of the soil should be tamped only lightly or left to settle on its own. Watering will assist in settling the soil naturally. Excessive tamping can cause soil compaction and slow water penetration and root growth.

Backfill soil amendments may be desired on sites with poor quality soil to improve soil structure, water-holding capacity, or drainage. On sites with high quality soil, the backfill does not require amending.

Watering
In the first year or two, it is important to keep the root ball moist, but not over-watered. The root ball soil is the major source of water for the tree until the root system redevelops. During this time, monitor the moisture in the root ball. Surrounding soils where there are few roots absorbing moisture often stay moist while the root ball quickly dries out.

The use of tree watering bags is gaining popularity, because they deliver water to the right place. But we know very little about heat buildup on the trunk under the empty bag. An empty bag may also deflect rainwater away from the base of the tree.

Throughout the warm, summer weather, the tree will probably need water about twice each week. Approximately 5-10 gallons (20 - 40 l) of water is sufficient to moisten a 20-inch (50 cm) diameter root ball. A 40-inch diameter root ball has more than twice the volume and would require 35-45 gallons (130 - 170 l).

Trunk Protection
Plastic guards can help to protect trunks from mowers, weed whips, and other mechanical injuries. If used, they must be removed before the trunk grows large enough to be damaged. Where sunscald or frost cracks are common, trunks of thin and/or smooth-barked trees are sometimes wrapped to prevent injury from winter sun. The preferred wraps are light in color, porous to water and biodegradable, and should be removed in the spring, no later than May 15 in the Chicago area.

Staking
Staking, guying, or bracing refer to mechanically supporting the trunk of a planted tree to keep it in an upright position. Staking is usually unnecessary for properly handled and planted B&B stock. If the root ball is in good condition and has been stabilized by firming the soil around the base, the tree is not likely to lean or shift. Many contractors feel that leaving the burlap and twine over the root ball for the first year helps to hold the root ball together and keep the tree straight. There may be a few exceptions where staking is needed, such as very windy sites, sandy root balls, or the potential for vandalism.

If a tree must be staked, be sure stakes and guys do not create a tripping hazard for people. Guying material should be wide, smooth, nonabrasive, flexible, and if possible, photodegradable. To prevent injury to the bark, the guying should be examined at least once during the growing season and adjusted if necessary. Supports should be removed after one year to avoid trunk girdling.

Mulching
Apply mulch over the entire planting hole to conserve soil moisture. The mulch layer should be 1-3 inches (2-7 cm) deep after settling, depending on the size of the tree. Mulch should not be allowed to cover the base of the trunk.

Mulch is often incorrectly piled up to 1 ft. (30 cm) deep in a small cone only about 3 ft. (90 cm) wide around the tree. This is sometimes called "volcano mulch". Volcano mulch is of little benefit to the roots, sheds water, can be potentially damaging to the trunk, and it is aesthetically unpleasing.

Sometimes volcano mulch may be covering up a bad planting job or hiding excess soil from the planting hole that was piled around the base of the tree rather than being hauled away.

Fertilization
Drought stress limits the growth of newly planted trees more than any other factor. Until the root system can grow and absorb more water, adding fertilizer to the soil is likely to be ineffective.

Additional Information and photos
http://www.ina-online.org/treespecsinstallation.html

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Research Briefs
Edited by Len Phillips

The Influence of Nitrogen Fertilization on Waterlogging Stresses
Glynn C. Percival and Ian P. Keary

The aims of this study were to determine the influence of nitrogen (N) fertilizers on tree tolerance under prolonged waterlogged conditions and investigate the effect of N fertilization on aiding tree recovery from waterlogged damage using containerized English oak (waterlogging-intermediate) and European beech (waterlogging-sensitive) as test species. English oak proved to be more waterlogging-tolerant than European beech.

N content was consistently higher in trees in which N fertilizers were added to the waterlogged solutions compared with trees waterlogged with tapwater only for 18 days. The addition of N induced greater resource allocation in favor of roots over shoots in both tree species. At the cessation of the 18-day waterlogging period and after a 10-day regeneration period, growth was constantly higher in N waterlogged trees compared with non-N waterlogged ones.

In a separate study, recovery rates of trees over a 6-week period after the cessation of 18 days waterlogging were 30% to 50% higher in N-fertilized trees compared with non-N-fertilized trees. In all cases, nonfertilized trees had the least capacity for recovery. In addition, leaf area, shoot, root, and total plant dry weight were higher in N-fertilized trees compared with nonfertilized ones.

Results of this investigation indicate:

1. applications of N fertilizers enhance the tolerance of trees under prolonged waterlogged conditions;

2. applications of N fertilizers after waterlogging stress would be of benefit to improve tree recovery rates and growth.

From a practical point of view, N fertilization of 14.5 g (0.51 oz) or greater N per liter (0.26 gal) of water is tentatively suggested based on preliminary results of this study.

Arboriculture & Urban Forestry Volume 34, Number 1 January 2008

Attitudes of Residents Toward Street Trees Before Removal of Ash Trees
Joseph Heimlich, T. Davis Sydnor, Matthew Bumgardner, and Patrick O’Brien

Residents in an area with mature street trees, including ash, scheduled for removal as a result of attack by emerald ash borer were surveyed to determine their attitudes toward their street trees. Large trees with a variety of summer and fall foliar characteristics were highly valued suggesting that residents would be satisfied with a mix of species rather than planting each street to a single species. The fact that their trees canopied the street was also important to residents and is characteristic of larger urban trees. Residents would be pleased if replacements were planted before removing existing trees. Flowers were not a significant concern for residents. In many communities, the primary maintenance concern regarding trees in this survey is the potential damage to sidewalks.

Arboriculture & Urban Forestry Volume 34, Number 1 January 2008

The Potential of a SPAD Meter to Quantify Nutrient Stress in Leaves
Glynn C. Percival, Ian P. Keary, and Kelly Noviss

The chlorophyll content meter (or SPAD meter) is a simple, portable diagnostic tool that measures the greenness or relative chlorophyll content of leaves. Compared with the traditional destructive methods of chlorophyll extraction, the use of this equipment saves time, space, and resources.

The objective of this study was to establish a correlation between chlorophyll content, total leaf nitrogen (N) content, and chlorophyll fluorescence Fv/Fm values with the SPAD meter readings in leaves displaying visual symptoms of N deficiency. In addition, this study determined a critical foliar N content below which a reduction in photosynthetic efficiency occurs.

Results of this study indicate that the SPAD meter offers a potentially useful nondestructive, hand-held system to aid in the evaluation of tree health. However, users should be aware of the limitations of this system. Inconsistencies in sample collection and seasonal timing may necessitate species and cultivar calibration equations to correlate SPAD values with reductions in tree vitality.

Arboriculture & Urban Forestry Volume 34, Number 2 March 2008

Tree Pulling Tests of Large Shade Trees
Brian Kane and Peggi Clouston

Shade trees provide many benefits but can cause damage if they fail. Despite the potential for costly litigation that sometimes arises when damage occurs, there are no investigations of bending moments and stresses involved in failure of shade trees. Twenty-four shade trees of three species in the genus Acer were pulled to failure. The maximum load and distance to failure were used to calculate maximum bending moment; stress at the point of failure was calculated from bending moment and stem cross-sectional dimensions. No trees uprooted, and failures were categorized as either stem at a lateral branch(es) or the attachment of codominant stems.

Failures of codominant stems required one-half the stress of stem failures. Similarly, failures of codominant stems occurred at only 45% of wood strength, whereas stem failures occurred at 79% of wood strength. Prediction of maximum bending moment from tree morphometric data was more reliable than prediction of maximum stress from tree morphometric data. Prediction of maximum bending moment and stress was more reliable for stem failures than codominant failures. Results are compared with similar tests on conifers.

Arboriculture & Urban Forestry Volume 34, Number 2 March 2008

Injected Treatments for Management of Madrone Canker
Marianne Elliott and Robert L. Edmonds

Pacific madrone (Arbutus menziesii) has been experiencing a decline in the Puget Sound area, primarily as a result of a canker disease caused by the fungus Fusicoccum arbuti. Cultural methods such as prevention of stress and wounding are recommended to control canker diseases on these trees. In addition, injection treatments can be used to protect valuable Pacific madrone trees in urban areas.

Two treatments that were effective in minimizing canker growth in inoculated madrones were Arbotect® and BioSerum™. Cankers on wound inoculations were 50% smaller than the control group and no infections occurred on surface-inoculated treatments. Increased callusing was observed on cankers on trees with these treatments. The mode of action for these chemicals is probably stimulation of plant defenses rather than fungicidal action. BioSerum™ is recommended in addition to cultural methods that improve tree vigor for high-value madrone trees in urban landscapes. Heavily infected trees that have lost most of their crown will probably not benefit, however.

Arboriculture & Urban Forestry Volume 34, Number 2 March 2008

Producing Bare Root Trees
Bonnie Appleton

Research is being conducted on 2-inch (5 cm) caliper trees to discover a better establishment rate with bare rooting than with balled and burlapped stock. Bare root trees growing at a nursery reduce the impact on the land from soil removal, and they fare better at the landscape site because of minimal loss of fibrous roots from ball damage. Bare root trees also have the advantage of lighter weight for reduced handling and shipping costs.

Nursery Management and Production December 2008

Root Pruning and Stability E. Thomas Smiley

Two root-pruning methods simulated construction-related trenching and individual root cuts such as from decay after root pruning. Utility trenching was simulated with linear cuts across the root zone. The trees were then pulled to failure to determine their stability. Measurable decreases in force applied occurred when cuts were within three times the trunk diameter from the trunk. Force decreased by 35% when a tangential cut was made at the trunk. When individual roots were severed, the pull force was reduced with each root cut. When one root was severed, the decrease in force averaged 12%; when half of the exposed buttress roots were severed, the decrease was 30%.

Arborists should avoid cutting any tree roots near the trunk. Linear trenching should not be closer to the trunk than a distance equal to or greater than three times the trunk diameter.

Arboriculture & Urban Forestry Volume 34, Number 2 March 2008

Attitudes of Municipal Officials toward Street Tree Programs Tyler R. Stevenson, Henry D. Gerhold, and William F. Elmendorf

Survey responses from municipalities in Pennsylvania defined the developmental status of municipal street tree programs and the attitudes of officials. In sustained programs which had an ordinance, tree commission, inventory, and management plan, officials had more positive attitudes about trees than in developing programs which had at least one of these elements, or in communities without a tree program. However, even in the latter, approximately half of the officials believed that benefits of street trees outweigh costs and disadvantages, and 62% favored starting a tree program. No tree programs exist in 46% of the cities, 82% of the boroughs, and 97% of the townships, so there are many opportunities but also important barriers.

Incomplete understanding of the benefits of trees and tree care practices leads to low public support, insufficient funding, and inadequate personnel and equipment. Most officials favor spending some money on trees but regard tree programs as less important than other civic responsibilities. Officials may be persuaded to start or improve tree programs by explaining benefits more fully; explaining how public safety can be improved by proper pruning; how inventories can locate dangerous trees; and how management plans arrange tree care requirements. Furthermore, costs may be alleviated by using volunteers, grants, and available technical advice.

Arboriculture & Urban Forestry Volume 34, Number 3 May 2008

Mulching of Ornamental Trees: Effects on Growth and Physiology
Francesco Ferrini, Alessio Fini, Piero Frangi, and Gabriele Amoroso

Two organic mulching materials applied to newly planted trees were evaluated for effects on tree growth and physiology. Both mulches were efficient in maintaining a cleared area around newly planted trees, although pine bark was more durable than coarse compost from mixed green material.

Trees mulched with compost generally had greater height, trunk diameter, and current-year shoot growth. Mulching with compost increased carbon assimilation of leaves when compared with pine bark and chemical weeding. Both mulching materials increased transpiration. Little effect on gas exchange was found. However, because mulched trees were larger with longer shoots, whole plant leaf gas exchange was probably greater. Mulching had very limited effects on chlorophyll fluorescence. Results of this project have shown that mulching materials applied around trees after planting can positively affect tree growth without significantly affecting tree physiology.

Arboriculture & Urban Forestry Volume 34, Number 3 May 2008

Experimental Tree Planting on U.K. Containment Landfill Sites
Andy Moffat, Kirsten Foot, Fiona Kennedy, Martin Dobson, and Geoff Morgan

A series of experiments was set up in England in the early 1990s on five containment landfill sites engineered to modern standards to test the relative performance of 14 native and nonnative woodland tree species. Their survival, growth, and nutrition were monitored over a 10-year period, and this article describes the results. The experiments demonstrated that several species, notably ash, whitebeam, white poplar, and wild cherry, can usually be established on landfill sites with survival rates comparable to other brownfield sites. Despite general site infertility, growth of many tree species (for example, ash, beech, English oak, sycamore, Italian alder, silver maple, white poplar, and whitebeam) was similar to that expected on greenfield sites in the locality of the landfill sites. As well as infertility, soil droughtiness and mammal browsing were identified as limiting tree performance of particular species on some sites. After 10 years, there was no evidence of interaction with landfill containment systems or landfill gas.

Arboriculture & Urban Forestry Volume 34, Number 3 May 2008

To earn ISA-CEU’s for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA science credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.

The Monetary Value of Trees
By Robin Morgan

Almost everyone knows that trees and other living plants are valuable. They beautify our surroundings, purify our air, act as sound barriers, manufacture precious oxygen, and help us save energy through their cooling shade in summer and their wind reduction in winter. Many people don't realize, however, that trees have an economic value, a dollar value, that can be measured by competent tree appraisers.

The basis for the value of an urban tree could be emotional, aesthetic, or it could be strictly utilitarian. Because trees are valued for many different reasons and people seldom perceive their value as strictly monetary, it is often difficult to assign a dollar value to trees. In many communities, public spending on tree care and management reflects an approximate value of trees. Spending patterns that go unchallenged, especially among an informed public, indicate the value people associate with trees.

Monetary Value
Urban trees often have substantial monetary values. A number of studies have shown that real estate agents and home buyers assign between 10% and 23% of the value of a residence to the trees on the property. Local governments capture some of this monetary value because enhanced property values increase assessed value and the tax base.

Appraisal methods have been developed for landscape plants, including trees. The standard for estimating the monetary value of landscape vegetation, usually accepted by insurance companies, courts, and public agencies, is "Valuation of Landscape Trees, Shrubs, and Other Plants: A Guide to the Methods and Procedures for Appraising Amenity Plants". This guide was prepared by the Council of Tree and Landscape Appraisers and published by the ISA.

A tree appraisal consists of four factors:

1. Size and age - Professional arborists use a specialized appraisal formula to establish value based on tree size and age.

2. Species or classification - Trees that are hardy, durable, highly adaptable, and free from objectionable characteristics are most valuable. They require less maintenance; they have sturdy, well-shaped branches, and pleasing foliage. Tree values vary according to the hardiness zone and local conditions.

3. Condition - The professional arborist will consider the condition of the tree. A healthy, well-maintained plant has a higher value. Roots, trunk, branches, and buds all need to be inspected.

4. Location - Functional considerations are important. A street tree may be worth more than one growing in the woods. A tree standing alone often has a higher value than one in a group. A tree that is a focal point in the landscape tends to have more value. The site, placement, and contribution of a tree to the overall landscape help determine the overall value of the plant attributable to location.

All of these factors can be measured in dollars and cents. They can determine the value of a tree, specimen shrubs, or evergreens, whether for insurance purposes, court testimony in lawsuits, or tax deductions.

Value of Services to the Urban Environment
Sewage treatment costs could be cut by applying treated effluent to trees and other landscape plantings. Irrigating with recycled waste water reduces the need for costly evaporation ponds and sewage lagoons, as well as the dumping of municipal wastes into rivers, lakes and oceans. Water-loving species could serve as natural water pumps for areas with high water tables. (Editor's Note: As stated in the first article of this Seminar, be sure to test the water to confirm that total dissolved salt levels are acceptable. Excessive total dissolved salts are toxic and can severely burn foliage and kill trees.)

Trees can cut energy costs by shading buildings and pavement, which reduces the temperatures in and around buildings. By cutting air-conditioning costs, trees indirectly reduce carbon dioxide emissions equivalent to fifteen times the amount the tree could absorb. Three well-placed trees can cut air-conditioning costs by 10% to 15%. For every ton of new wood that grows, about 1.8 tons (1.7 mT) of carbon dioxide is removed from the air and 1.3 tons (1.2 mT) of oxygen is produced.

Tree Planting
There are about 100 million available tree planting spaces around American homes and businesses. Planting trees in these spaces could reduce atmospheric carbon dioxide by an estimated 18 million tons (16 mT) per year, and save consumers $4 billion each year in energy costs. The cost of reducing carbon dioxide through tree planting is about 0.3¢ to 1.3¢ per pound of carbon dioxide.

Urban forest managers must become adept at communicating the services of urban trees if their requests are to compete for an appropriate share of local budgets. Powerful computers that retrieve and summarize information can help them generate and communicate this information.

Sources

• Morgan, Robin, "The Value of Trees", World Forestry Center in Portland, Oregon, March 1993

• "Tree Values", Tree Care Information, ISA, September 2005

To earn ISA-CEU's for this article, click on TEST for Certified Arborist, Utility Specialist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA management credits. The ISA will award you with 0.5 CEU's when you score 80% or better on the test. Be sure to add your ISA cert. no. after your name when you sign in.