BR Planting with an Air Spade
Edited By Len Phillips

The air spade was originally developed by the military to clear land mines. Air spade technology was introduced to the tree industry and promoted mainly to diagnose and treat root problems. The air spade is a great product for blowing soil away from a tree's trunk without harming the roots. "

Using an air spade, an arborist can locate the original trunk flare of a tree planted too deeply, reveal girdling roots that may be threatening a tree's health, or a host of other uses, outlined below. All of this without damaging roots or buried utility lines. The air spade allows nursery workers to lift the entire root system when digging a tree and planting it bare root. The technique is especially useful for moving trees from tight spots that can't be reached with a mechanical spade.

The air spade uses an air compressor to generate a high velocity jet of air to dislodge the soil, but it leaves the roots intact. Most compressors will generate 150 cubic feet (42 cubic m) per minute or more-pumped into a 3/4 inch (2 cm) hose, from which it is delivered through an aperture the size of a pencil, in order to move soil, debris and rock while preserving and protecting the root system.

Uses of the air spade include:

• root collar/trunk flare excavation

• root damage investigation

• checking adequacy of root structure

• inspection and correction of root health concerns

• inspection of girdling roots

• inspection of improper planting techniques

• quick, accurate diagnosis of root diseases

• determine extent of decay without extensive root system damage

• bare root transplanting

• aeration or soil compaction reduction

• soil tilling

• vertical mulching

• preparation for soil amendments to promote root growth and survival

• radial trenching

• locating roots for utility line installation

• utility locating and repair

Transplanting Trees
The air-spade is being used for transplanting trees and shrubs. It is considered a viable option to transplanting with a tree spade or by the balled and burlapped method. Air-spade technology of bare root transplanting enables crews to remove a tree from the ground while keeping intact roughly 95% of the tree's root system. This method greatly improves the probability that the tree will survive the move. The air spade is especially useful for transplanting specimen trees.

Digging Procedure

1. Before using the air spade, hydrate the trees deeply for 72 hours prior to preparation for the transplanting. Clay soil blows best when it is damp while sandy soil blows best when it is drained, but still moist.

2. The minimum root ball should be at least 20 inches (52 cm) of root mass diameter for every caliper inch (2.5 cm) of trunk diameter.

3. Begin the process by digging a perimeter trench at the end of the roots. The soil from the air spade will be blown into the trench.

4. As the air spaded tree roots are uncovered, they are sprayed with water and covered with wet burlap.

5. When all the roots are exposed, they are gathered and attached by ropes to the trunk, in "pony-tail" fashion.

6. A forklift picks up the tree, under the trunk, and moves it and all the roots to the new location.

7. The roots are released and spread back in their original position.

8. The planting proceeds as it would with any bare root tree.

This transplanting technique should result in most of the tree's roots being retained. This greatly reduces the transplant shock and speeds the recovery of the tree.

Example
A large birch was air spaded in the heat of midday. With an eight foot (2.4 m) diameter root mass, the tree was lifted, relocated and then replanted. After it was backfilled, the tree and planting pit was flooded with water. Despite the hot, sunny weather and exposed location, there was no evidence of wilting. Two weeks later the transplanted birch remained settled in its new location without any sign of stress.

Advantages/Disadvantages

• The advantages of using an air spade include saving 80% - 95% of the tree's roots.

• Compare this to 5% - 10% of the roots in a hole dug for B&B or 30% with a tree spade.

• Minimizing root loss minimizes transplant shock.

• Air spade transplanting requires more labor than a tree spade but less labor than B&B.

• Air spade transplanting has lower equipment costs than a tree spade, but more than B&B.

• The tree survival rate is higher using the air spade method. Part of the reason for this is that roots do not easily grow from one soil type to another, but since the bare root process provides a uniform mix of soil that is typical of the new location, the tree can easily adjust.

Sources

• Personal communications with Matt Foti
• Howe, Deborah ASLA, "Roots First", Landscape Architecture Magazine, March 2009.
• Howe, Deborah ASLA, "The Bare Necessities", Lawn & Landscape Magazine, February 2009.

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Tree of the Seminar
Edited by Len Phillips

'Bessoniana' Black Locust is one tough tree for urban sites. It has good disease resistance, fast growth, and excellent year-round form. 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: Robinia pseudoacacia 'Bessoniana'
Trade Name: 'Bessoniana' Black Locust
Parentage: An older variety of European origin
Family: Fabaceae
Year of Introduction: Unknown
Height: 30'
Spread: 20'
Form: Compact, oval shape
Bloom Period: May to June
Flower: White clusters, fragrant, desired by honeybees
Fruit: Black pods
Spring Color: Late to leaf out in spring
Summer Foliage: Medium green in summer
Autumn Foliage: Yellow in fall
Winter Color: Bark provides winter interest
Bark: Dark gray bark, dark brown stems, thornless
Habitat: Species found in mid-Atlantic States west to Iowa and Oklahoma
Culture: Tough and adaptable to poor soils by fixing nitrogen
Hardiness Zone: 4 - 8
Growth Rate: Rapid but considerably slower than the species, up to 2' per year
Pest Resistance: Susceptible to several diseases and insect problems, more vigorous trees have less trouble with pests
Storm Resistance: Excellent due to very tough wood
Salt Resistance: Excellent salt resistance and urban pollution tolerance
Planting: Easily transplanted B&B or BR
Pruning: Late summer to fall due to excessive spring bleeding
Propagating: Budded onto species understock
Design Uses: Good for urban sites, city street tree, not recommended for home landscapes
Companions: Excellent with coarse textured perennials such as Hosta
Other Comments: Much more symmetrical than the species, improved crotch angles, almost completely free of spines, well behaved, excellent in New England
Available From: Difficult to find in most nurseries, look in the largest wholesale nurseries or be prepared to wait a few years for better availability. J. Frank Schmidt & Son has only 50 trees at the present time
Photos: J. Frank Schmidt & Son

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Tree Growth Regulators
Edited by Len Phillips  

There are two kinds of manufactured Tree Growth Regulators (TGRs). Invented in the 1950s, Type One TGRs stop cell division on contact. Many of the herbicides used today are made from these materials. Type One TGRs can be very effective for preventing unwanted sucker sprouts. If applied systemically, they will cause disfigurement and so they are best applied through aerosol sprays.

Type Two TGRs were developed in the 1990's and work quite differently than the Type One. Instead of inhibiting cell division, Type Two inhibits cell enlargement. The cells remain wholly intact, except for their size. The number of cells produced by the tree also remains the same.

A Type 2 TGR is a chemical that suppresses the production of gibberellin, the plant hormone that is responsible for cell elongation in the growing tips of trees. Both abscisic acid and gibberellic acid are produced from the same starting material, so when gibberellic acid formation is decreased, abscisic acid production increases. Abscisic acid induces responses that protect the tree and help plants withstand and respond to environmental stresses. The effects of increased abscisic acid include stimulation of stomatal guard cell closure and an increase in the defense response of the tree. Higher levels of abscisic acid are believed to be responsible for increased root growth, thicker leaves, and the increased drought tolerance exhibited in the treated trees. In addition, the amount of carbon dioxide that enters the leaf is reduced, limiting photosynthetic capacity during optimal conditions. When conditions become stressful, the benefit of improved water relations allows photosynthesis and other metabolic functions to proceed in treated plants while untreated plants shut down.

Paclobutrazol
Paclobutrazol (PBZ) is a Type Two TGR. Arborists know this product as Profile 2SC or Cambistat®. Both of these products are described below for your information and convenience only. No endorsement or any statement of claims about these products is assumed by Online Seminars. Likewise, these descriptions do not constitute an approval of these products to the exclusion of others.

PBZ applications significantly slow the growth of a tree but do not eliminate growth or the need for tree pruning. The application of PBZ will reduce the growth of a tree by 30 - 80%, depending upon the species of tree and the application rate.

PBZ applications extend the trim cycle interval between prunings and reduce the amount of pruning needed.

The use of a PBZ on trees directly under power lines will enable utilities to maintain their systems on a longer pruning cycle with minimal encroachment of branches that could cause an outage.

PBZ use has been shown to alter the allocation of resources from the production of leaves to favor root growth and the production of defensive chemicals. This may increase a tree's ability to survive insect and disease attacks and to withstand environmental stresses like pollution and drought. Reducing growth with PBZ reduces the amount of energy spent on shoot growth and may stimulate fine root development.

One theory as to why these growth retardants give trees protection from drought is that thicker leaves have more water holding capacity, and more roots can gather and store more water. Thicker leaves have a smaller percentage of exposed tissue than thinner leaves and because treated leaves have a lot more trichome hairs covering the stomata, there may be a physical obstruction to water loss.

PBZ has also been used to stimulate root regeneration after transplanting, and it has been studied for the purpose of stabilizing declining trees that have insufficient fine root development. Treatment should be part of a complete tree care program that includes mulching.

Laboratory and field evaluations over the past 30 years have shown that PBZ does not leach into groundwater. The chemical is tightly bound to soil particles, and only trace amounts of the chemical have been identified in the soil below 16 inches (40 cm), even after months of heavy rain. Leaves and wood chips from trees treated with PBZ can be used for mulch without adverse impact on other plants.

Profile 2SC
Profile 2SC is injected into the ground and is absorbed through the less suberized roots just below the soil line. Here the bark is more permeable due to a thinner cork layer. In addition, breaks in the outer root tissue created by normal growth processes provide pathways to the xylem. It is then carried in the transpiration stream to the tree crown. This closed injection environment reduces product exposure to people and wildlife. It appears that, by reducing tree stress, Profile 2SC may give the tree greater ability to withstand some harmful conditions. Profile 2SC is not highly mobile in soil; it remains localized at the points of application for up to 12 months after treatment. The majority of the solution stays within the top 16 inches (40 cm), with only trace movement downward. Based on research, it can be concluded that groundwater contamination is unlikely.

Cambistat®
Cambistat® is a soil-applied TGR that is used in the arboricultural industry to reduce tree growth 40% to 60% over a three year period from a single application, and provide some relief for trees in stressful sites. Studies have demonstrated that Cambistat® enhances rooting, increases tolerance to drought, and reduces the incidence of certain diseases. Treated trees have reduced growth; thus trimming cycles can be extended significantly and a lot of money is saved.

Application
Cambistat® is best applied to the tree at the soil/trunk interface. This can be done by pouring a drench into a 2" - 4" (5 - 10 cm) deep trench at the base of the tree. The roots of the tree will absorb the chemical and disperse it through the tree's crown to suppress the subsequent growth of the tree.

There is no injury to the tree from TGR application. Every species of tree that has been studied to date has been assigned a letter on a rate chart that signifies the dose of Cambistat® that is needed to give it the right amount of growth control. There are 6 categories from A to F. When the Cambistat rate chart is followed, each species will be getting the correct amount. Too much PBZ on sensitive trees can result in too much growth control. While this will not harm the tree, it can result in a tree that may not be very pleasing to the eye.

The affect of TGR applications will take several months or longer to become apparent. The first effect that will be noticed is an enhanced greening of the leaf, because PBZ stimulates the tree to produce more chlorophyll. Growth reduction of the tree can take longer and often becomes apparent the season following application. The crown of a treated tree is typically more dense and compact than an untreated tree.

Risks
The application guide and rate chart that comes with the PBZ product is updated with information coming from companies using the material, and it is very important that these guidelines be followed. PBZ must be applied correctly - too much PBZ or poor application technique can make a tree grow too slowly. This results in small leaves and a "poodle" effect. The tree will not die and it will eventually grow out of this condition, but people can become alarmed and upset when this happens.

Benefits of Slow Growth
Slowing down the growth of a tree conserves energy. Less energy is spent on top growth, which means more is available for reserves, roots, defense, etc. One of the myths that people have about trees is that fast growth is a sign of good health. Health from a tree's perspective is more related to energy than growth. Slower growing trees tend to have higher levels of energy than faster growing trees of the same species.

Urban Trees
Urban trees are surrounded by underground obstacles that prevent their root systems from becoming as large as they would in unconstrained locations. Add to this the problem of poor soil quality (compaction, herbicides, low organic matter and nutrients) and it becomes clear why urban tree lifespans are so greatly limited. A tree's lifespan is not determined by a biological clock but by the tree's ability to make enough energy to support its living mass. Once they reach a "critical size," trees become too large to be supported by the environment in which they live. They then begin to decline.

Residential yard soils have a poor capacity to support tree roots. Turf is so competitive that tree roots in lawns are literally half as abundant as in the forest. This limits how large a tree can get before it will start to decline. Research has shown that removing the turf and laying down a 3-inch (5.5 cm) layer of mulch under the tree's canopy will double the root system in that area. A healthier soil will increase the capacity of the site to support a larger and healthier tree, with significantly more roots.

There are many reasons why a tree may show symptoms of decline, including soil compaction, irrigation and drainage problems, herbicide damage, grade changes, etc. If the cause of the decline is not addressed, then treatment with a TGR is unlikely to have the desired effect. A TGR should be used in conjunction with other arboricultural practices such as radial trenching, vertical mulching, and fertilization to correct mineral deficiencies, etc.

Leaf Disease Impacts
A number of studies have shown that PBZ can help prevent disease infection of leaves. While the exact mode of this protection is not known, there are two theories that may explain this.

1. The first theory is that the morphological changes of the leaves of treated trees (thicker leaves, more trichome hairs, and more chlorophyll) change the disease/leaf interaction. Many tree diseases are highly specific to certain kinds of trees, so by changing the leaf morphology there may be a lack of "recognition" by or susceptibility to the disease that infected it.

2. A second theory is that the increase in trichome hairs creates a physical barrier to disease infection. To understand this, first understand how leaves catch fungal infections. Basically, a fungal spore comes through the air and lands on the leaf. When it gets moisture and the temperature is right, the spore hatches and a little tentacle (mycelium) comes out and grows in an attempt to get into the leaf before the moisture disappears. PBZ doesn't prevent infection, but it can significantly prolong the time needed for an infection to develop.

Bacterial leaf scorch
Bacterial leaf scorch (BLS), caused by Xylella fastidiosa, is a destructive disease that affects a number of economically important tree species in the eastern, southern, and mid-western United States. Oaks, elms, sycamores, maples, sweet gum, and mulberries are among the tree species that this disease affects. Symptoms can first be noticed in early summer, but usually increase and intensify throughout the growing season and become even more pronounced under moisture-limiting conditions. Most trees with BLS usually display decreased vigor and slowly decline over a number of years.

Bartlett Tree Research Laboratories has been conducting research on the use of PBZ for suppression of BLS with very promising results. PBZ has been shown to suppress the decline associated BLS on five different trees, but additional research is needed. It is interesting to note that the treatment has no impact on the bacteria itself. It is speculated that by changing the morphology of leaves and making them more drought tolerant, the bacteria's effect of dehydrating the tree is reduced.

Sources

• "About Profile 2SC", SePRO Corporation, 2010.

• Bai, Shuju, William Chaney, and Yadong Qi, "Response of Cambial and Shoot Growth in trees Treated with Paclobutrazol", Journal of Arboriculture 30(3): May 2004.

• Burch, P. L. and R. H. Wells, "Tree Growth Evaluated 10 Years After Application of Paclobutrazol Tree Growth Regulator", Down to Earth, Vol. 50, No. 2.

• Prosser, Tom, "Understanding Tree Growth Regulators", Tree Care Industry, February 2006.

• Rappahannock Electric Cooperative, "Tree Growth Regulators", 2006.

• Rainbow Treecare Scientific Advancements, "Tree Growth Regulator Treatments", 2003

• Sperry, Chad E. and William R. Chaney, "Tree Growth Regulator Effect on Phototropism", Journal of Arboriculture 25(1): January 1999.

• Watson, Gary and E. B. Himelick, "Effects of Soil pH, Root Density, and TGR on Pin Oak Chlorosis", Journal of Arboriculture 30(3): May 2004.

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Mycorrhizae
Edited by Len Phillips

Mycorrhizal fungi are naturally occurring fungi that prefer the soil in the woods. Mycorrhizae (my-ka-RY-zee) are not exactly a root and they are not exactly a fungus; they fall halfway between. By definition, mycorrhizal fungi are highly specialized organisms that colonize the fine, non-woody roots of plants and they act as extensions of roots. By extending the roots, the tree's absorptive surface is increased up to 700%.

The mycorrhizae association occurs when the fungi grow around a root and invade the outer layer of root cells. The fungi then act like root hairs to extract minerals from the soil. In poorer soils, the fungi explore the soil extensively in search of nutrients, more efficiently than root hairs, and translocate them back to the root for absorption and use by the tree. In exchange, the tree will "pay" for this service by providing the fungus with sugar from photosynthesis. The fungi can also absorb soil moisture more easily and increase a tree's drought tolerance. A soil full of mycorrhizal fungi seldom has bad fungi or disease issues.

The area near the roots is called the "rhizosphere", and is the thin layer of soil that sticks to the roots. The rhizosphere is a huge habitat in the soil, because plants have so many fibrous roots. At least 100 million organisms live in each gram of soil, but in the rhizosphere, there may be a trillion organisms per gram.

Benefits of Mycorrhizae
The relationship between the fungi and the tree roots is wholly symbiotic. In exchange for extending the plant's roots, the mycorrhizal fungi obtain carbohydrates, vitamins, and amino acids from their host plant. Compared to non-colonized roots, mycorrhizal roots have been shown to:

• grow faster,

• live longer,

• be more physiologically active and energy efficient,

• absorb water and accumulate nutrients better,

• improve uptake of phosphorus,

• make plants more resistant to drought,

• increase tolerance to soil compaction,

• increase tolerance to high temperatures,

• increase tolerance to salt and toxic materials,

• increase tolerance to extremes of pH,

• increase tolerance to root diseases,

• increase flower production and hardiness,

• decreased transplant shock,

• deter bacterial and fungal pathogens and parasitic nematodes,

• increase tolerance to organic and inorganic soil toxins,

• provide a conversion of atmospheric nitrogen to soluble nitrogen fertilizers,

• provide a conversion of insoluble minerals, notably rock phosphate, into soluble forms that can be readily absorbed by tree roots.

Hyphae
Hyphae are the vegetative structures of fungi. They look like tubes. A term for certain hyphae is mycelium. Hyphae from mycorrhizae on one tree can connect with hyphae from mycorrhizae attached to another tree of a different species. Hyphae grow around soil particles, binding them together to provide voids for air, water, and tree roots.

Glomalin
Glomalin is the unique fungal protein that holds soils together. The gooey protein is secreted through hyphae. Glomalin sloughs off of the hyphae and finds its way into soil. It coats soil particles and holds them together as aggregates or small grains of soil. Glomalin can be as high as 2% of the total weight of a soil aggregate.

Types of Mycorrhizae
Mycorrhizae can be divided into groups:

• Ectomycorrhizae (ECM) is a group of fungi that form a mantle or sheath around the cortical cells of short lateral roots. ECM fungi grow thick coats of mycelia around the rootlets of trees and bring water and minerals from the soil into the roots. In return the host tree supplies the fungi with sugars, vitamins, and other root substances. This relationship occurs in more than 80% of all plants. ECM colonize the roots of conifers (pines,hemlocks, spruces)and hardwoods(oaks, beeches,chestnuts, hickories, and birches). Depending on the type of mycorrhizal relationship, infected trees may have an advantage at obtaining soil water and nutrients. Some species of ECM are limited by geographical area. As with plant materials, the origin of the fungus is very important when considering purchase of inoculums. The majority of ECM grows best between 64°F (18°C) and 80°F (27°C), though some have a wider temperature tolerance. Pisolithus tinctorius, for example, can grow at soil temperatures of 93°F (34°C) or higher. ECM fungi are generally visible to the eye. 

• Endomycorrhizae are fungi that penetrate cortical cells of fleshy young, roots but form no mantle or sheath. This relationship may be beneficial to both parties or may be harmful to one of them. Endomycorrhizal fungi colonize less than 20% of all plants. Endomycorrhizae are associated with a variety of trees and shrubs such as magnolia, maples, apple, birch, ash, and American elm. 

• Ectendomycorrhizae are those fungi that both penetrate root cortical cells and form root-surrounding mantles. 

• Arbuscular Mycorrhizal Fungi (AMF) are found in all climates and ecosystems, regardless of the type of soil, vegetation or growing conditions. It is found on the majority of cultivated plants. AMF populations can be altered by urbanization. This modification can take place in the soil environment, particularly under landscape irrigation, which reduces AMF colonization on some tree roots. AMF can increase tree carbon storage potential, although this capacity in managed residential landscapes might be somewhat less than in undisturbed soil. Ultimately, the ability of AMF to increase tree growth is likely a function of tree species and factors such as water availability and enhanced phosphorus uptake. AMF are important components of terrestrial communities, but the basic ecology of individual AMF remains unclear. Taxonomic differences were apparent in the amount and proportion of fungal biomass found in roots versus in soil. The results indicate that the colonization strategies of AMF differ considerably based at the family level. 

• Vesicular Arbuscular Mycorrhizae (VAM) has unique vegetative and reproductive life stages and is a type of endomycorrhizae. During their vegetative stage, they develop a hyphal matrix comprised of runner, penetrating, and absorbing hyphae. VAM fungal hyphae explore the soil beyond the root zone and acquire phosphorus for roots. Researchers are learning from VAM fungi that it is inadequate to measure the efficiency of mycorrhizae solely in terms of phosphorus nutrition or an enhancement of plant growth. Plants recently transplanted into a landscape could benefit more from VAM fungi that promote root exploration rather than promote shoot growth. The VAM fungus suppressed shoot growth and the thickening of roots may be a drought survival mechanism promoting storage of carbon reserves in roots until drought conditions improve. Research with mycorrhizae and trees has been conducted in greenhouse environments. There is little information on the function of VAM in field environments. This same research indicates a mixture of easily cultured fungi (AMF and/or ECM) may not have any predictable benefits in the field. 

Urban Soil
Urban soils are generally missing key soil components, including mycorrhizae. This is a soil that has been dug up, stripped of topsoil, compacted, and generally abused. These are the places where mycorrhizae are really needed.

Since 1994, numerous companies have manufactured mycorrhizal fungal spores in a variety of products, serving as mulch, liquid root dip, or soil injection. All of these products include an array of mycorrhizal fungi designed to stimulate root growth. Early research indicated that trees receiving root inoculations showed greater growth, but those inoculated via the injection method were double the average growth of the control trees. Other experiments introducing mycorrhizal fungi to plants have generally failed to demonstrate significant improvement in tree growth. The best results have been in highly disturbed soils, where native mycorrhizae populations are unnaturally low. However, combining mycorrhizal inoculations with fertilizer is more effective than using either treatment alone. Soils cannot be inoculated with mycorrhizae, but soils can be inoculated with the fungi that infect roots to form mycorrhizae.

Even with the appropriate fungus, fertilization, liming, pesticide use, and topsoil removal can adversely affect the beneficial effects of the fungus. Mycorrhizae will not perform efficiently in highly fertilized soils. Therefore the tree has to rely on less efficient root hairs, which reduce the effectiveness of the fertilizer. Mycorrhizal fungi are not a panacea for poor soils.

Most plants form mycorrhizal associations without any human interference. Even in disturbed soils, mycorrhizal fungi will be introduced naturally over time as wind and animals carry fungal spores into the area. Introducing mycorrhizae in urban soils may help but the species introduced will likely be different than what the plants will eventually develop on their own.

Tree planters have been known to simply add a shovel full of local forest duff into their planting holes. Forests contain plenty of native fungi in the ground. You may also use a shovel full of soil from nearby sites where similar trees are doing well.

In poor soils, consider amending the soil with compost instead of adding mycorrhizal fungi because it improves drainage, adds nutrients to the soils, and naturally contains microorganisms that may also colonize plant roots.

Sources

• Appleton, Bonnie Lee, "Mycorrhizae", City Trees, Vol 37, Number 6 November/December 2001.

• Appleton, Bonnie, et. al., "Mycorrhizal Inoculation of Street Trees", Journal of Arboriculture Vol. 29, No. 2 March 2003.

• Buschena, Cindy, "Will Mycorrhizal Inoculations Save Your Ailing Tree", Minnesota, ADVOCATE • Summer 2000.

• Carlson, Julie, et al, "Can Mycorrhizae Improve Tree Establishment in the Landscape?", SNA NewsLine, November/December, 2000.

• Hart, Miranda M. and Richard J. Reader, "Variation In Arbuscular Mycorrhizae Fungi" New Phytology 2002. 153:335-344.

• Kernan, Michael J. Ph.D., "Biological Treatments for City Trees", City Trees, Vol 40, Number 3 May/June 2004.

• Keslick and Son, "Technical Tree Biology Dictionary", Modern Arboriculture, Associates, 2008.

• Little, Jane Braxton,"Mycorrhizae: Unsung Heroes", California Trees, Winter 2003 Vol. 14 No. 4.

• Spafford, Anne, "Mycorrhizae", Landscape Architecture, February, 2001.

• Stabler, Linda B. et al., "Urbanization Effects on Tree Growth", Journal of Arboriculture 27(4): 193-202.

"Transplanting and Root Growth", City Trees, Vol 38, Number 1 January/February 2002.

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Tree Care after Planting
Edited by Len Phillips 

After planting a balled and burlapped tree, the transplant shock period is approximately one year for each inch (2.5 cm) of stem caliper. Therefore, a three-inch (8 cm) caliper tree will need at least three years in the landscape to recover from the shock of being moved. However, if the planting site is particularly harsh, typical for many urban planting sites, this shock period may be much longer. Climate and soils are also factors which alter the shock period.

The transplant shock period should be considered as the period of intensive care. Maintenance practices should focus on eliminating or reducing all unnecessary stresses such as water stress (too much, too little), competition for root space from other plants (especially turfgrass), insect pests or pathogens that wound or defoliate the tree, nutrient deficiencies, and unnecessary wounding.

Follow-Up Care
The following five factors are all relatively simple and much more cost-effective than repair work and replacement after the tree has become larger but unhealthy and untrained:

• good planting practices,

• watering,

• mulching,

• preventing injury,

• proper pruning.

After planting, be sure to indicate on maps and/or lists the trees planted at their given locations. Then remove the nursery tags from the trees and shrubs to prevent girdling the branches and/or trunks. Properly mulch newly planted trees and shrubs. Apply no more than 4 inches (10 cm) of mulch to help keep the moisture in the ground. Mulch also protects the root zone from severe cold or severe heat, and it encourages mycorrhizae formation on the roots. Mulch should be kept at least 6 inches (15 cm) away from the trunk. Only stake trees with large crowns, those situated on windy sites, or where people may push them over. Remove the stakes after one year. If the tree is wrapped, remove the wrapping the first spring after planting.

Ideally, all trees should be inspected annually and cared for regularly. If a tree dies, care should be taken to determine the cause before another tree is planted. If poor drainage is a problem, it should be corrected if possible. If vandalism is a problem, have neighborhood kids help plant larger trees in these areas. The kids will develop a sense of "ownership" which will help protect the tree from future vandalism attacks. Also, add a large stake, 5 feet (1.5 m) tall, beside the tree to help protect it for its first two years. To offset the higher cost of planting larger trees in difficult locations, many municipalities plant smaller trees in parks and residential areas where vandalism is less likely to be a problem. In areas of high pedestrian traffic, it may be necessary to install pavers, stone, or brick set in sand over the tree ball. This will have a negative impact on the tree's growth but will allow it to continue growing (albeit more slowly).

Tree grates
Tree grates have been used for decades around the base of trees in downtown business districts. Tree grates help support the growth of the trees and strengthen their resistance against harmful environment influences. They are designed to present a level surface for pedestrians and cyclists and support their weight while preventing soil compaction over the roots. They also keep the soil, mulch, or gravel that is traditionally placed around the top of the root ball from spilling out onto the sidewalk. Tree grates also add a formal structural element to the design of the streetscape. They are not for sustainable landscapes but are a short-term solution for downtown landscapes and should be replaced about every 15 to 20 years as the tree trunk grows into it. Tree grates are less appropriate for park settings where there is usually suitable soil space for roots.

Pruning
Start proper pruning one or two years after planting. When pruning the top of
the tree, determine the desired shape of the tree, prune to remove dead branches, and correct structural weaknesses. Summer is a good time to remove water sprouts and suckers and to check the tree for dying or rubbing branches, pedestrian traffic on sidewalks, truck damage on street trees, or power lines when the weight of full foliage bends the canopy. Winter is the best time for structural pruning to encourage a well-balanced branching pattern, solid branch attachments, and a strong single leader.

Watering
Trees provided with regular irrigation through the first growing season after transplanting require approximately 3 months in hardiness zones 9-11, 6 months in hardiness zones 7-8, or one year or more in hardiness zones 2-6 to fully establish roots in the landscape soil. During this period, the tree's energy should be focused on rapid root growth. Transplanted trees rely almost entirely on root ball moisture for most of the first growing season, and because the root balls dry out more rapidly than the surrounding backfill, root ball irrigation is critical. According to recent research, for the first 4 weeks after planting, a 1-gallon (4 liter) tree requires 1 pint (½ liter) of water per day. During the next 11 weeks, 1 quart (1 liter) is used per day and for the next 21 weeks ½ gallon (2 liters) of water is used per day. However, after this point, depending on the hardiness zone, the roots should have grown into the enlarged root zone so specific root ball irrigation is no longer necessary.

Irrigation helps maintain and encourage a desirable dominant leader on a large-maturing tree. Trees that are under-irrigated during the establishment period often develop undesirable, low, and double leaders that can split from the tree later.

Root Regeneration
Root regeneration occurs soon after transplanting and refers to the replacement of roots that were cut and lost during the digging process. These new roots grow in the same direction as the original roots. The rate of regeneration varies depending primarily on soil moisture, soil type, temperature, and species. Easy-to-transplant species such as green ash will initiate new roots in 17 days or less. Red oak, a species difficult to transplant, will take 24 days to start new roots. Cool soils take a longer time to develop good root systems than warm soils. In the upper Midwest where soils are frozen in winter, tree roots grow an average of 18 inches (0.5m) a year. In Florida's sandy soils and a year-round growing season, roots will average 6 feet (2m) a year.

Once a tree is established, many roots will have grown an eventual distance equal to approximately 3 times the tree's height. During the establishment period, shoots and trunk grow slower than they did before transplanting. When their growth rates become more consistent from one year to the next and the growth rate returns to the level before transplanting, the tree is considered established.

When roots of bare-root trees and containerized trees are not spread out properly at planting, permanently kinked and twisted roots can result. Proper root development and anchorage will not occur, and vascular flow may be restricted. During the transplanting process, primary roots are cut so the existing branch roots often begin to grow more rapidly. This results in a more fibrous root system, typically found on nursery grown trees.

Winter Care
Winter sun, wind, and cold temperatures can bleach and desiccate evergreen foliage, damage bark, and injure or kill deciduous branches, flower buds, and roots. Snow and ice can break branches and topple entire trees. Salt used for deicing streets is harmful to trees and landscape plantings. Salt runoff can injure roots and be absorbed by the plant, ultimately damaging the foliage with too much salt. Salt spray from passing autos can also cause severe foliar or stem injury. Be sure there is plenty of spring rains to wash the salt off the foliage and flush it from the soil. If there is not, it will be necessary to provide irrigation. To prevent this problem, avoid planting salt-sensitive trees and shrubs in highly salted areas.

Tree Health Inspections
Various physical features can be observed to indicate the survival and general well being of a newly planted tree, including the foliage, twigs, bark, and roots. The color of the foliage is an excellent diagnostic indicator. A uniform bright green color over the entire crown with leaves fully formed is a reliable indicator of good health on hardwood species. Yellowing indicates water stress from too little or too much soil moisture or may indicate various degrees of nutrient deficiencies. Yellowing and immature leaves early in the spring usually indicates stress due to water logged soil during the dormant season. This condition commonly occurs on trees planted in compacted soils.

Diagnosis for moisture stress of conifer foliage is somewhat more difficult. Examination of the soil condition and roots may determine if moisture stress is a cause. Length of twig elongation as compared to previous growth is another indicator of plant health. Some twig shortening should be expected due to transplant shock. Planting a tree too deep can be fatal, cause rotting, and eventual failure or unwanted sprouting.

Though root examination is difficult, it is recommended when serious growth symptoms appear. The color of healthy, vigorous tree root tips is white to light yellow, with smooth surfaces. Root tips affected by poor aeration are dark brown, purple or even black and have rough-looking surfaces.

These few tips stated above will help ensure success to newly planted trees.

Sources

• Clatterbuck, Wayne K. "Post-Planting Tree Care: Fallacies and Recommendations", Wildlife & Fisheries, Agricultural Extension Service, The University of Tennessee. 2005.

• Gilman, Edward F., "Planting trees in landscapes", Environmental Horticulture Department, IFAS, University of Florida, 2004.

• Johnson, Gary, "Establishing New Trees", Department of Forestry, University of Minnesota. 2006.

• Marzalina, E. Philip, M. and P.N. Avadhani, "Recovery Patterns Of Transplanted Trees", Arboricultural Journal, 2002. 26:9197.

Struve. Daniel K. et. al., "Survival Of Transplanted Red Oaks", Journal of Arboriculture, 26(3): 162-169.

Robinson, Lana, "Prep Trees Now for Growth Next Year", TCI Magazine, September 2003.

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Planting Grow-Bag Trees
Edited by Len Phillips 

Grow-bags are a cylindrical bag made from geo-textile or poly-mesh and have been a mainstay in nurseries and greenhouses for years.. They are often used by nurseries and containerized tree growing operations to restrict the spread of tree roots. The bags are usually the final stage of producing plants that have a dense fibrous root system without the girdling and circling roots of traditional container growing. Grow-bags are also called in-ground fabric bags, root control bags, and fabric containers. They can be used above ground or in planting holes. They feature heavy-duty plastic construction, are often fluted, have pre-punched bottom drainage holes, and easily stand upright when filled with soil mix. They are capable of withstanding several years of weathering. When used above ground, the black plastic absorbs the sun's rays, which heats up the soil mix, and subsequently encourages faster, stronger growth. Properly planted and harvested, the final plant is less susceptible to transplant shock, quicker to establish, and more vigorous in the landscape.

Grow-bags range in size from small hanging versions to large specially-treated plastic bags that hold up to 11 gallons of soil. They are most commonly available in 1, 3, and 5-gallon sizes. To use them below ground, holes are augured in a field, the bags are "planted" to about 7/8s their depth, backfilled with the augured soil, and then planted with a tree or shrub. The bags stimulate extensive fibrous root growth with a higher survival rate than trees grown in rigid containers. However, trees grown for too long in the bags will become root-bound just like container grown trees.

Grow-Bag Grown Trees
Most nurseries that produce trees in grow-bags, use field soil. Irrigation and fertilizer applied only to the top of the root ball will help increase roots in the ball better than irrigation and fertilizer applied to a larger area around the container. Typically, root balls grown in grow-bags are harvested from the ground in the dormant season and potted into containers. Less commonly, they are sold directly to the landscape industry. Root balls of field-grown trees contain the same amount of roots as those grown in grow-bags except that grow-bag root balls are less than half the volume. Grow-bags small volume makes these trees easier to handle but because the root ball is smaller, there is less water storage capacity. Combined with a dense root system, this lesser reserve makes trees produced in grow-bags more sensitive to desiccation immediately after digging than trees grown directly in field soil. Nursery operators should make provisions for delivering the irrigation needed to prevent desiccation immediately after harvesting. A complaint about trees in grow-bags for too long is that roots that penetrate the bag are badly damaged when the bag is separated from the root ball at planting time.

Some growers produce trees in grow-bags above ground. The fabric allows air and the fabric itself to prune roots. The result is a reduction in the amount of circling roots

Digging
Trees grown in grow-bags are easier to lift than the same size trees balled and burlapped (B&B) because they have a smaller root ball. However, their roots are easily broken, unlike those in rigid plastic containers, so the bag should be wrapped like a B&B plant and the trees handled very carefully.

Handling at the Landscape Site
Because grow-bag trees require more frequent irrigation and require staking to hold them up, grow-bag trees are rarely planted directly into the landscape because of the likelihood of mishandling and poor understanding of the product. Soil inside the ball can become loose from just a moderate disturbance. Never drop the ball, because if the roots lose contact with the soil, the tree may go into shock and be more likely to die quickly. Always remove all the fabric before carefully sliding the root ball into the planting hole. Some container designs allow only small-diameter roots to develop outside the fabric. Fabric on these trees must be removed without disturbing the root ball. A hand pruner can be used to cut large-diameter roots flush with the inside of the fabric to make removal easier.

A new in-ground fabric container allows for the lateral exchange of water between the native soil and the container. It is also coated with an herbicide that keeps the roots from growing through the fabric. No root loss should occur at harvest, whereas up to 20% of the roots may be lost using other types of in-ground grow-bags. But if trees are received with grow-bags still attached to the root balls, they must be removed at planting to prevent root deformation.

Pros of Grow-Bags

• Smaller ball size makes grow-bags easier to handle,

• Transplanting to a container does not require a full growing season for tree recovery,

• Grow-bags provide the quality of top growth that can only be achieved in the field, and does so with the convenience and mobility of plants grown in containers,

• Grow-bags can be used over and over again,

• No heavy equipment or tree spades are necessary,

• Because a tree has not been in a grow-bag for numerous years, the circling roots of conventional containers are not a problem,

• Grow-bags are great for plants like Leyland Cypress that have easily damaged, fibrous root systems.

Cons of Grow-Bags

• Grow-bags create more fragile root balls than the root balls of B&B trees,

• Grow-bags dry out faster than the root balls of B&B trees,

• Grow-bags require staking when planted directly into the landscape.

Growing trees in the field in grow-bags and then establishing them in containers before sale, provide the maximum energy for root growth. Plant grow-bag trees into the landscape between May and September and by the following summer the trees are established. Losses are few, stress tolerance is high, and customer satisfaction is excellent.

Sources

• Botanica Fine Gardens and Landscapes, "Grow bags", Jelsoft Enterprises Ltd., 2009.

• Gilman, Edward F. "Fabric container grown Trees", ENH870, Environmental Horticulture Department, University of Florida.

• Gilman, Edward F., "Planting trees in landscapes", Environmental Horticulture Department, IFAS, University of Florida, 2004.

• Watson, Gary W. and E. B. Himelick, "Principals and Practice of Planting Trees and Shrubs"', International Society of Arboriculture, Savoy, IL 1997.

• Whitcomb, Ph.D, Carl E, "Optimal Tree Growth", The Master Plantsman, Issue 2.

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Staking, Guying, Stapling, and Wrapping
Edited by Len Phillips 

Staking
Current practice dictates that a tree should not be staked unless wind is a problem or the tree develops a lean. Then it can be supported with a flexible stake or guy wire that will permit the tree trunk to sway in the wind. Young trees standing alone with their tops free to move will develop stronger, more resilient trunks than those staked for several years. The stem may in fact become thicker from long term staking above the tie than below it because diameter growth increases in response to the movement of the crown. When a tree can only flex above the tie, it is also easy to snap off by using the tie as a pivot point.

A supported tree will initially gain height faster than an unsupported tree, but the stem will be thin and weak up to the tie and then it will taper rapidly. Normally, when a tree bends as a result of wind, root development on the windward side of the tree is increased, thereby aiding the tree in becoming stronger and eventually straightening up on its own. Recent research has discovered that a tree in a windy location actually develops an oval cross section to deal with prevailing winds. This cannot occur if the tree is staked or guyed.

If a tree must be staked, all stakes and guy wires should be removed between 12 and 18 months after planting, provided the tree can stand straight. A staking system is one that secures new trees up to 20 feet (6 m) tall with long stakes driven into the soil on either side of the root ball. From the stakes, a short bracing collar or other device holds the tree in an upright position. A tree is not likely to be girdled by the attachments in one growing season, but if they are left on for more than a year, they will girdle a tree or weaken it.

Street trees may need staking to stabilize them against jostling from pedestrian traffic. Street trees are best supported with two stakes, set parallel to the curb, so that pedestrians are not hindered. Every newly planted tree should be assessed individually to determine whether or not it should be staked. When stakes are used, the tree should be "tested" at the end of the first year by being pushed back and forth. If the tree stands upright and the trunk is rigid at the soil line, the stakes should be removed.

Staking Systems
Staking systems can vary from inexpensive wood stakes with guying material to very expensive manufactured guying systems. One system uses a unique, one-stake support with a flexible tree bracing collar that allows for natural sway movement and lessens the likelihood of trunk injury. In addition, the single stake is easy for one person to install, is reusable, does not detract from the beauty of the tree, and is not a pedestrian trip hazard. The common characteristic of any staking system is that it requires time to install and maintain.

Tree bracing collars should be smooth, wide, flexible, and not abrasive in any way. One of the best attachments is made of soft nylon webbing or carpet strips attached by grommets to a stake. The old practice of using a piece of garden hose covering a cable is no longer recommended due to the damage the hose can cause to the bark. The tree bracing collars should be located within the first third of the distance up the trunk.

The stakes can be made of any material but 2" x 2" lumber is the usual favorite. To prevent damage to the root ball, stakes should be placed in the ground beyond the outer edges of the ball.

Staking may be appropriate:

• when new trees are extremely large or have abnormally small root systems that can't physically support the larger above-ground growth and the tree can't be returned to the nursery,

• when the stem is spindly and bends excessively if it is not supported and the tree can't be returned to the nursery,

• when the tree is a palm that may require staking due to a small root ball,

• when the planting site is very windy and trees will be uprooted if they are not supported,

• when there is a good chance vandals will uproot or damage unprotected trees,

• when the tree is planted in sand or other loose-textured soils.

Cons of Staking

• Stakes detract from the desired look of the landscape,

• Trees need to move without restriction from the ground up,

• Staking causes some trees to break and can also restrict the flow of sugars by crushing the cambium,

• Often the staking system is not adjusted properly or is left on the tree for too long, causing damage to the tree,

• Staking requires labor to install, maintain, and remove,

• Staking requires periodic inspections and adjustment as needed to avoid damaging the tree.

Guying
Trunk stabilizing with guy wires has been the traditional method for stabilizing newly planted trees for centuries. It is believed that trunk stabilizing came with the trees that were lashed to the decks of early trade ships.

A guying system secures new plantings by long wires running from the ground to the first third the distance up the trunk where the wire is secured around the trunk. This system is designed for trees exceeding twenty feet (6 m) in height, all evergreens over 8 feet (2.5 m), and uses turnbuckles and earth anchors. Recyclable tree bracing collars made of flexible plastic or nylon tape, manufactured for this purpose, or twist braces that allow for flexibility of the tree trunk should be used instead of hose and wire. Otherwise, a guy wire that is too tight around the trunk can girdle and kill the tree.

Cons of guying

• Wires detract from the desired look of the landscape and often require flagging to prevent tripping,

• Trees need to move without restriction from the root collar,

• Guying places unnatural stress at the point where the guying materials attach to the trunk,

• Often the guying material is not adjusted properly or is left on the tree for too long,

• Girdling occurs where the tree begins to grow around the offending guying materials, absorbing them into the trunk,

• Trunk stabilizing requires labor to install, maintain, and remove.

Biodegradable Guying System
One inexpensive guying system consists of using wire that is a soft No. 9 wire put in a 2"x18" (5x45 cm) length of carpet, creating an open loop around the tree trunk. The wire is attached to a softwood stake that is not painted or treated. The wire is applied so that the tree trunk touches the inside windward edge of the open loop, allowing the tree trunk a limited freedom of movement in almost every direction. This staking method completely breaks apart after 18 months and eventually rots away, eliminating the need for follow up maintenance at sites were none will be available.

Below-grade Stabilizing
A below-grade system that secures new plantings by the root-ball is called stapling. A long "staple" is placed through the root ball to hold the ball in contact with the bottom of the planting pit thereby holding the root system in place. When the roots are stabilized, there is improved root growth and the trunk is allowed to move in response to surrounding conditions. Below-grade stabilizing reduces the chance that newly sprouting roots will be broken off during wind gusts that might twist the entire tree. Staple manufacturers indicate that the metal staple can be removed after one season or, if left in place, will eventually rust away. Staples can also be built out of three pieces of wood nailed together into a staple shape.

Pros of Stapling

• There are no above ground obstructions and the desired look is immediate,

• No maintenance or disposal is required because there is no need to remove the staples,

• Some below-grade staples can be installed with a sledge-hammer in as quickly as 1 minute,

• There is nothing to constrict the trunk, eliminating the risk of girdling, bark damage, and potential breaking from stress due to guying materials.

The American Nursery and Landscape Association (ANLA) encourage all municipalities, landscape architects, and landscape installers to consider using root staples. Research has shown that trunk stabilization may be detrimental to a tree's growth but when secured by the root-ball, trees flex through the length of the trunk. They develop a better overall taper and become more tolerant of wind and vandalism.

Cons of Stapling

• Unless a metal staple is removed after a couple of years, it will be a problem if the tree is removed and the stump and roots are ground out. Grinding equipment could be severely damaged if it hits the metal staple.

Wrapping
Most trees do not need to be trunk wrapped except in extremely harsh sites or to protect thin-barked trees. If a tree comes from the nursery with a wrapped trunk, remove the wrapping after planting. If wraps are desired, they should be removed within one year. To avoid trunk girdling, do not attach wraps with wire, string, nylon rope, plastic ties, or electrical tape. If cared for and maintained properly and regularly, wrapping materials are worthwhile. Replanting the tree in the same compass orientation as it was in the nursery can minimize sunscald.

Pros of Wrapping

• Many arborists think that sunscald may be prevented with white tree wraps on thin-barked trees (ex. maple, birch, cherry, and beech) especially if trees are planted on southern exposures or paved areas that reflect heat.

• A wrap is useful in preventing injury during digging and transplanting.

Cons of Wrapping

• Gas exchange is limited,

• Moisture is retained between the wrap and the tree trunk,

• Wrapping provides a habitat for insects, disease, and water damage to tree trunks,

• If there is a layer of green cortex beneath the bark that contains chlorophyll that functions to trap energy from the sun, this bark should not be covered.

• Sometimes wrap is used to hide wounds.

Unfortunately, there is still a lot of controversy surrounding the use of tree wrap for winter protection. No harm will come from placing light-colored wrapping on stems in late autumn and removing it in early spring, but the cold-damage benefits are debatable. To prevent rodent damage, install a plastic or woven wire collar around the stem instead of tree wrap. Trees that are water-stressed going into dormancy are more likely to suffer bark splits. Tree shelters or growing tubes are better than tape because they allow sunlight and air to flow around the bark.

Trunk injury from equipment causes serious damage to trees. Regular weed control in a large diameter circle around the trunk, such as layer of mulch, is the best way to protect the trunk of a recently planted tree. Stakes protect the tree from accidental injury.

Sources

• Appleton, Bonnie Lee, "To Stake or Not to Stake?" Landscape Architecture, April 2004.

• "Basic Tree Biology", City Trees, The Journal of The Society of Municipal Arborists Vol. 37, Number 6 November/December 2001.

• British Trust for Conservation Volunteers, "Tree Planting and Aftercare",www.btcv.org/skills 2009.

• Clatterbuck, Wayne K, "Post-Planting Tree Care: Fallacies and Recommendations", Wildlife & Fisheries Agricultural Extension Service, The University of Tennessee, 2006.

• Gilman, Edward F., "Planting trees in landscapes", Environmental Horticulture Department, IFAS, University of Florida, 2009.

• King, John, "Staking versus Tree Staples", City Trees, Vol. 38, Number 6 November/December 2002.

• King, John, "How to Stabilize Newly Planted Trees", City Trees, Vol. 40, Number 1 January/February 2004.

• Miller, Robert S. "Bare Root Tree Planting Advantages", City Trees, Vol. 39, Number 5 September/October 2003.

• Quinn, W., "Should Newly Planted Trees Be Staked and Tied?" ANLA Memorandum, Purdue University Extension Service, June 21, 2002.

• Spafford, Anne, "Tree Staking and Guying", Landscape Architecture, November 2000.

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Research Briefs
Edited by Len Phillips 

Deep-Rooted Trees for Urban Environments
David W. Burger and Todd E. Prager

Seedling liners of three tree species were planted in the field and grown for 18 months. Air spade excavation showed there were significant differences in root architecture among the three species and within each species' population. Among the three species, Pistacia chinensis had, on average, the deepest, most vertically oriented root systems and Fraxinus uhdei and Zelkova serrata the shallowest.

Furthermore, there were shallow-rooted and deep-rooted genotypes within each species. Shallow-rooted and deep-rooted genotypes of Fraxinus and Zelkova selected from the seedling populations were propagated vegetatively by cuttings, planted in the field, and grown for 5 to 6 years. On excavation, the root architecture of the cutting-propagated clones was assessed. Cutting-propagated clones of shallow-rooted parents were shallow-rooted; thus, they maintained the parents' root architecture. Cutting-propagated clones of deep-rooted parents were also shallow-rooted; they did not maintain their parents' root architecture.

Arboriculture & Urban Forestry Volume 34, Number 3 May 2008

Winter Hardiness and Salinity Tolerance
Glynn Percival and Sally Barnes

A field trial was undertaken to determine the influence of seven commercially available calcium fertilizers on a). the winter hardiness and b). the freezing and salinity tolerance of two tree species, evergreen oak (Quercus ilex) and apple (Malus cv. 'Golden Crown'). In all cases, the application of calcium foliar sprays increased twig, leaf, and root growth, plus freezing and salt tolerance of both species. In the case of apple, a hardiness gain was recorded in twig tissue. In the case of evergreen oak, a hardiness gain was recorded in leaf tissue. After freezing, cell damage was less in calcium-treated trees compared with non-calcium-treated controls.

There was a positive influence of calcium on enhancing leaf tissue tolerance to salt damage. Differences in the magnitude of freezing and salinity tolerance gained were noticeable among the calcium products used. In general, calcium hydroxide, calcium nitrate borate, and calcium metalosate improved twig, leaf, and root freezing and salt tolerance in both tree species over calcium chloride, calcium sulphate, calcium nitrate, and a calcium-magnesium complex.

A significant correlation existed between increased freezing tolerance and internal tissue calcium content. This study indicated that calcium sprays during late summer and fall can increase the freezing and salinity tolerance of evergreen oak and apple during the winter. This should be considered noteworthy for individuals involved in the management of trees in areas subject to subzero temperature fluctuations and/or concomitant applications of deicing salts in the form of sodium chloride.

Arboriculture & Urban Forestry Volume 34, Number 3 May 2008

Planting BR Trees in Heat
Louis Anella, Thomas C. Hennessey, and Edward M. Lorenzi

Baldcypress, London plane, and Autumn Blaze® maple can be planted using the bare-root (BR) method with irrigation even where summer heat and drought create challenges for trees. Planting in spring has little, if any, benefit for the species studied.

These findings indicate that BR planting is not limited to cooler regions of the United States. Community forestry programs in the southern United States can benefit from the advantages offered by BR planting when drip irrigation is used. In this study, a crew of three people planted all the BR trees using a small tractor and a box blade in less time than a crew of five people working with a front-end loader could unload the same number of B&B trees from the trailer.

Arboriculture & Urban Forestry Volume 34, Number 3 May 2008

Bending Moment of Shade Trees
Michael Pavlis, Brian Kane, J. Roger Harris, and John R. Seiler

Arborists assume that pruning can help reduce the risk of tree failure by reducing the wind sail (drag-induced bending moment). We simulated wind by driving trees in the back of a pickup truck from 0 to 55 mph (0 to 90 kph) and measured drag-induced bending moment as well as tree morphometric data for Freeman maple (Acer × freemanii), swamp white oak (Quercus bicolor), and shingle oak (Quercus imbricaria). Measurements were taken before and after application of one of three pruning types (raising, reduction pruning, thinning). Reduction of drag-induced bending moment differed by pruning type, largely in accordance with the mass of foliage and twigs removed. The effectiveness of pruning types was also species-dependent because crown architecture affected how much mass each pruning type removed.

In general, per unit of mass removed, reduction pruning more effectively reduced the drag-induced bending moment than thinning or raising. Reduction pruning reduced the center of pressure height and, presumably, increased crown porosity after pruning.

Arboriculture & Urban Forestry Volume 34, Number 4 July 2008

Tree Stabilization Systems
Ryan Eckstein and Edward F. Gilman

We conducted pull tests on newly planted 2.8 in (7 cm) caliper, container-grown Quercus virginiana 'SDLN' Cathedral Oak® to simulate wind loading on nine commonly used landscape tree stabilization systems. Maximum force required to rotate the root ball 20° was used to compare systems.

Terra Toggle^TM, Brooks Tree Brace®, and 2 × 2's anchoring the root ball withstood the largest forces. Typically, trees secured by these three broke before the systems failed indicating that the systems were very effective. T-stakes, dowels, and Tree Staple^TM performed no better than non-staked controls. The three guying systems tested, ArborBrace®, Duckbill®, and rebar and ArborTie®, were statistically similar and required more force to failure than controls, but less than the group that withstood the largest forces. Direction of pulling had no influence on force to failure for any stabilization system tested.

Arboriculture & Urban Forestry Volume 34, Number 4 July 2008

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CRZ for Trees
Edited by Len Phillips

Field investigation and research in the last two decades have destroyed the myth that the root system extends only to the drip line of a tree's canopy. Another commonly held myth is that all mature trees have a taproot that is the most vulnerable portion of the root system. This is not true either. A tree's root system varies in width, depth, and structural characteristics with the species of tree as well as with soil characteristics and moisture levels.

Critical Root Zone Determination
The Critical Root Zone (CRZ) is the area under and beyond a tree's crown where many important roots lay just below the surface. These are the vital roots that collect nutrients and moisture for the tree and must be protected for the tree to survive. It is very important to determine the minimum area around a tree that must be left undisturbed during any event near the tree. The health of the CRZ can be damaged by:

• cutting roots,

• excavating surrounding soil,

• applying chemicals,

• compacting surrounding soil,

• applying any material that impedes the flow of water or air to the roots.

Some reports indicate that the CRZ is the same as the tree's drip line. Others indicate that the CRZ will typically be represented by a circle concentric to the tree's trunk with a radius equal in feet to one and one-half times the number of inches of the trunk diameter. For example, the CRZ radius of a 20-inch (50 cm) diameter tree is 30 feet (9 m) or 60 feet (18 m) in diameter.

However, the latest research indicates that in order to successfully determine the extent of the CRZ and to build in close proximity to significant or specimen trees, it is important to have an accurate depiction of a tree's underground structure. Relying on formulas or guesswork alone will not suffice when engineering a parking lot to the nearest inch in elevation, the edge of a paved surface, or the nearest fraction of a linear foot for a sewage line.

CRZ Formula
In order to determine the limits of the CRZ, a formula has been developed which is: (dbh of tree) x (Distance from trunk by condition rating from table below) = radius (in feet) of CRZ

CRZ Determination for Trees with a Condition Rating of 2, 3, 4, or 5 (5 being best)
                                                                                  Condition Rating    4 or 5           2 or 3
Species tolerance            Tree Age                                                       Distance from Trunk
Good                              Young (<20% of life expectancy)                       0.5’               0.62’
                                        Mature (20 – 80% of life expectancy                 0.75’             0.94’
                                        Over mature (>80% of life expectancy)              1.0’               1.25’
Moderate                       Young                                                                0.75’             0.94’
                                        Mature                                                                1.0’              1.25’
                                        Over mature                                                       1.25’            1.56’
Poor                                Young                                                                 1.0’             1.25’
                                        Mature                                                                1.25’            1.56’
                                        Over mature                                                        1.5’             1.88’

Note: For trees with a condition rating of 1 a determination should be made, with assistance of a qualified arborist, as to whether or not the tree can be saved or is worth saving.

Examples:
A mature 60-year-old, 32" dbh live oak (Quercus virginiana), with a Condition Rating of 4 (good species tolerance, mature age): 32 x 0.75 = 24' radius CRZ

A 15-year-old, 10" dbh yellow poplar (Liriodendron tulipifera), with a Condition Rating of 2 (poor species, young age): 10 x 1.25 = 12.5' radius CRZ

Because nature is variable, textbook answers will never be sufficient. Site investigation, combined with field experience, has always been necessary. Investigative digging and air spading are also a couple of common sense approaches employed by experienced urban forestry professionals.

Sources

• Matheny, N., and J. Clark, "Trees and Development. A Technical Guide to Preservation of Trees During Land Development", International Society of Arboriculture. 183pp. 1998.

• Minneapolis Park and Recreation Board, "Pruning Regulations to Protect the Critical Root Zone", 2010.

• Rathjens, Richard G. James A. Doolittle, Greg Mazur and Alan R. Siewert, "Ground-Penetrating Radar as a Tool for Diagnosing Shade Tree Soil Problems", TCI Magazine, November 2003.

• Stokes, Alexia et al, "Root System Investigation By A Radar Ground-Penetrating System", Journal Of Arboriculture, 28(1) Pg 2 - 10, January 2002.

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