Archive #32

Archive #32 from Online Seminars for Municipal Arborists (on-line-seminars.com) May/June 2010
ISA will accept test scores for articles in this Archive. If you would like the tests for this Seminar, please email lenphillips@yahoo.com for Test #32

List of Articles
Alternative Irrigation
Medicinal Properties of Trees
Tree of the Seminar
Dendrochronology
Tree Planting Pits
Tree Risk Assessment
Soil Management
Fertilization
Research Briefs
Summer Branch Drop

Alternative Irrigation
By Dena Kirtley

Dealing with Rainwater in the Past
Decades of massive urbanization have replaced a landscape receptive to rainwater infiltration, capable of replenishing underground aquifers, with large scale impervious surfaces that alter: flow paths, water storage, pollutant levels, rates of evaporation, groundwater recharge, surface runoff, the timing and extent of flooding, and the suitability and viability of aquatic habitats.

The traditional approach to urban runoff has focused on flood water management and runoff was conveyed as quickly as possible away from urban areas to waterways and rivers, to protect people and property. In most of California for example, runoff was, and in some areas still is, conveyed via drains along streets into agricultural ditches which would then take the water directly to the storm water treatment plant adjacent to a stream, river or ocean. Consequently precipitation induced runoff was seen as waste and not a resource.

Changing Attitudes
As we became aware of the demand for and value of water, storm water is now being viewed in an entirely different light. In a typical U.S. city where sometimes nearly 50% of the landscape is asphalt or concrete, a 1" rain event can produce more than 150 million gallons of water per square mile. Considering that many metropolitan areas cover over 1,000 square miles this represents an enormous untapped supply of water that could be available for irrigation.

Retention Basins
Strategies and plans are now being developed to capture and utilize this water. One such strategy is the development of storm water retention basins. These basins were initially designed to recharge groundwater and mitigate flooding, but they have now become attractive amenities within the urban landscape. Retention basins provide ecological habitats and are home to a diverse wildlife population. More importantly, they can provide recreational venues and they are a dependable alternative water supply. Even during a dry season, urban runoff adds to the naturally occurring accumulation of storm water thereby guaranteeing a reliable source of water suitable for irrigation. Most retention basins are built adjacent to new subdivisions where run-off from specific neighborhoods runs into them. They are also sometimes connected to existing agricultural ditches managed by State Reclamation Districts originally tasked with draining swampy land for farming. In West Sacramento, CA, almost all of our retention basins interconnect with State Agricultural Reclamation District ditches.

Water Quality
It is important to be cautious when considering storm water retention basins as a water source because the quality of water varies greatly. Adjacent landscapes often contain fertilizers, herbicides, pesticides, and fungicides. Parking lot and roadway surfaces are covered with motor oil, antifreeze, exhaust soot and other pollutants. Therefore, it is important to determine the quality of the water and the appropriate treatment (if any) before use.

Fortunately, nature provides a natural water treatment process within the wetland environment. Tule or bulrush acts to absorb pollutants and vent them into the atmosphere while bacteria and microbes breakdown and render other pollutants harmless. The use of tule and bulrush are being used as on-site basin treatment options in several urban areas. Mud and silt runoff is captured by the basin and these solids are retained for eventual removal by maintenance crews.

Site Selection Considerations
There are several conditions which need to be considered when assessing a site for use as an irrigation source:

there needs to be a constant supply of water,
the site needs to be accessible for installation of the basin and equipment to maintain it,
a power source needs to be close by,
the reclamation district or property owner needs to provide permission to draw water from the basin,
any potential ecological or environmental impact.

Irrigation Design
These retention basins or irrigation supply systems should be part of a regional design process from the beginning and therefore it is important to get the local planning department involved during the development process. During a major storm, flood waters collect on the streets and enter the city storm drain systems and are carried at maximum capacity to adjacent retention basins. When the basin fills to capacity, a series of pumps move the excess water to a "main drain canal" and then the water is pumped into the river.

Proper design of the irrigation system itself is also critical; the pumps and filters, valves, piping, sprinklers/bubblers, and proper identification signage must function safely and efficiently. Signage surrounding the basin identifies it as a raw water source and this is very important as is routine maintenance. If all of these conditions are met you will have a long-term, reliable, affordable, and sustainable water supply for your landscape.

Projects
Prior to the installation of retention basins, storm water was basically uncontrolled, running into any existing agricultural ditch and leaching into groundwater naturally. In the City of West Sacramento, our first storm water pumping projects were the MC-10 Lake Washington retention basins. These retention basins represented not only a leap in water resource management, but an aesthetically pleasing addition to the city's landscape. A total of three hundred and eleven trees that were 9 to 12 feet tall and came from the nursery in 24 inch boxes, were planted around the two basins. The trees consisted of native Valley Oak, Interior Live Oak, Sycamore, and Western Redbud. In addition, 10,000 sq ft of bunching fescue was planted within the project area.

The City-owned irrigation system supplying all the newly planted trees and grasses surrounding the retention basins are fed by a filtered pumping system out of the retention basins. At capacity, the system is capable of pumping 8 hrs a day for 20 days a month, which is an average irrigation schedule. This provides a total capacity of 768,000 gallons monthly. This irrigation system is owned by the city. When we first considered pumping irrigation water out of the retention ponds, the option of pumping the water from a well was a viable choice; however, it turned out to be far more expensive so the idea was dropped.

Future Goals
The size of basins to be built in new developments will be based on a calculation of hardscape to be installed and the amount of projected capacity needed for runoff. We have identified 14 additional retention basin sites within West Sacramento where this effort can be duplicated, averaging 750,000 gallons at peak monthly consumption per site for a total of 10,472,000 gallons a month. During the irrigation season we can save as much as 63 million gallons of potable water annually at just these 14 sites. Currently, no water is being used for irrigation at any of these sites.

Dena Kirtley has been the Urban Forest Manager for the City of West Sacramento since 2004 and a Certified Arborist since 1998. Dena has worked for non-profit Urban Forestry organizations, such as the California Urban Forests Council, the Sacramento Tree Foundation, and Tree Davis since 1994. Sam Cooney provided technical assistance to the article and is the Irrigation Specialist for the City of West Sacramento. He has worked in the irrigation industry for more than 35 years including running the central control irrigation system for the City of Rocklin.

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Medicinal Properties of Trees
Edited by Len Phillips

Trees contain many natural products that have medicinal properties, three of which are terpenes, tannins, and alkaloids. Besides their function in the tree, these chemicals have been used by humans for thousands of years for their medicinal properties. Some of the benefits derived from these chemicals are described below.

Terpenes
Terpenes are a large and varied class of hydrocarbons, produced by a wide variety of trees, particularly conifers. They are the major components of resin and turpentine. Vitamin A is another example of a terpene and steroids are derivatives of terpenes.

Terpenes are also the primary constituents of the essential oils that are used as natural flavor additives to food; as fragrances in perfume; and in traditional and alternative medicines such as aromatherapy. Research into terpenes has found that many of them possess ingredients used in pesticides.

When terpenes are modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compounds are generally referred to as terpenoids, also known as isoprenoids. Terpenoids represent the oldest and are probably the most widespread group of natural products derived from trees.

Some well-known products have been developed from modified terpenoids:

Polyterpenes consist of long chains of many isoprene units. Natural rubber is a polyisoprene.
Diterpenes form biologically important compounds such as retinol, retinal, and phytol. They are known to be anti-microbial and anti-inflammatory.
Tetraterpenes include the acyclic lycopene, the monocyclic gamma-carotene, and the bicyclic alpha and beta-carotenes.
Menthol, a monoterpene, is a topical pain reliever and antipuretic. Borneol and camphor are two common monoterpenes. Borneol, derived from pine oil, is used as a disinfectant and deodorant. Camphor is used as a counter irritant, anesthetic, expectorant, and antipruritic, among many other uses.
One of the most well-known medicinally valuable terpenes is taxol. Taxol is isolated from the bark of the Pacific yew, Taxus brevifolia. It acts to stabilize the mitotic apparatus in cells, causing them to act as normal cells rather than undergo rapid proliferation as they do in cancer.

Terpenes history spans various civilizations. As they are largely found in essential oils, they were used in ancient Egypt for various religions aims. Camphor was introduced in Europe from the East by the Arabs around the 11th century. The process of obtaining plant essential oils by fatty extraction was known by the early Middle Ages.

Tannins
The term tannin refers to the use of wood tannins from oak used to tan animal hides into leather. Tannins are astringent, bitter plant polyphenols that either bind or shrink proteins. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripe fruit or red wine.

When out in the open air hydrolysable tannins normally change to a brownish color and are used for the brown color of many plant dyes. The leaching of tannins from the decaying leaves of vegetation adjoining a stream may produce what is known as blackwater or brown swamp water.

Tannins are used in dyeing, photography, and as an astringent in medicines. Tannins are added to various processed foods, including ice-cream and caramel. They are also used to precipitate proteins in wines and beer. Tannins form a vital element of tea and coffee and consuming too much of these beverages without milk may lead to calcium and iron deficiency in the body that often leads to osteoporosis and anemia. However, adding milk or lemon juice to the tea helps in reducing or neutralizing tannins’ adverse actions on iron intake.

Tannins are physically located in the vacuoles or surface wax of plants as well as in the tree bark, wood, fruit, pod, leaves, and roots. These storage sites keep tannins active against plant predators, but also keep some tannins from affecting plant metabolism while the plant tissue is alive. It is only after cell breakdown and death that the tannins are active in metabolic effects.

The other remedial values of tannins include application on burns to heal the injury and on cuts to stop the bleeding. While it stops infection on the skin surface, internally, tannin continues to heal the wound. In case of third degree burns using strong tannin sources will not only prevent septicemia, but also helps to save a life. On the other hand, when a tannin-rich solution is poured on the flesh, it generates a sealing 'eschar' that often helps in growing new skin. This technique requires repeated washing of the wound with tannins and this also helps to eliminate the bacteria. Hence, tannins are also said to have antiseptic properties.

Herbs possessing tannins are widely used as mouthwashes, eyewashes, snuff, vaginal douches, and to treat rectal disorders. When applied internally, tannins affect the walls of the stomach and other digestive parts. They sour the mucus secretions and contract or squeeze the membranes in such a manner that secretions from the cells are restricted. The good thing is that tannins’ anti-inflammatory effect helps to control or curb all indications of gastritis, enteritis, oesophagitis, and irritating bowel disorders.

Tannin repels insects and herbivores. Bacteria and fungi cannot grow on anything containing or treated with tannin. Most significantly, tannins destroy the microbe’s metabolism process by depriving them of iron and other metal ions through restriction of oxidative phosphorylation.

Alkaloids
Alkaloids are naturally occurring chemical compounds containing basic nitrogen atoms. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals. Many alkaloids often have pharmacological effects and are used as medications. Examples are cocaine, caffeine, nicotine, morphine, and quinine. Besides, being venomous, the primary function of the alkaloids in all vegetation appears to be to protect the plant from grazing animals and herbivorous insects.

Each variety of alkaloid has its own distinct quality:

Pyrrolidine alkaloids – are basically derived from the amino acid called ornithine. This cluster of amino acid comprises the tropane alkaloids, atropine, hyoscine, and hyoscyamine from the family of nightshade plants.
Pyridine and piperidine alkaloids – are a group of alkaloids which comprise numerous species of toxic plants that include poisonous hemlock (Conium maculatum), tobacco (Nicotiana tobacum) and water hemlock (Cicuta douglasii). Poisonous hemlock is one of the most aggressively lethal indigenous plants found in North America. This plant is often mistaken for a parsnip root and in this case the chemicals present in the plant effect the central nervous system directly and most often leads to death.

Pyrrolizidine and quinolizidine alkaloids – are a group of alkaloids that have always proved to be of immense pharmacological interest for researchers and clinical examiners. All these alkaloids are known to have lethal features and may prove to be fatal. Pyrrolizidine is known to be injurious to the liver.

Indole alkaloids – comprise the anesthetizing alkaloids of the passion flower, ophthalmic alkaloids associated with the physostigmine derived from the calabar bean as well as the uterine tonics such as ergotamine. This variety of alkaloids also comprises the Indian snakeroot (Rauwolfia serpentaria) that consists of reserpine, a potent hypotensive and depressive chemical. Indole alkaloids are central nervous stimulants such as strychnine, psilocybin and johimbine as well as in the mind jerking medication LSD.

During the Middle Ages, hundreds and thousands of people in Europe were badly affected by a malady known as ergotism also known as ‘St. Anthony’s Fire’. The main symptoms of this disease included festering extremities, spasms, and insanity. These people suffered from the malady as they consumed bread prepared from rye that was infected with indole alkaloids.

Bufotenine – another indole alkaloid is widely present in Yopo seeds which are used as an hallucinogenic snuff. Bufotenine is also called tryptamine and is also found in the skin discharges of particular toads of the Bufo species and this offers an explanation regarding the practice of some people licking toads.

Vinblastine and vincristine – are two more varieties of indole alkaloids that are found in the Madagascar periwinkle (Catharanthus roseus). These alkaloids have proved to be very effective for chemotherapy patients suffering from leukemia and Hodgkin’s disease, by terminating the tumor cells, hence, resulting in a reduction of the cancer. Since researchers have started utilizing this alkaloid for treating the disease, there is a 90% possibility of survival.

Quinoline alkaloids – are quinine from the bark of Cinchona ledgeriana. The alkaloid quinine is a treatment for malaria. There are people who still take prophylactic doses of bitter quinine water (tonic) in the evenings, habitually mixed with vodka or gin.

Isoquinoline alkaloids – are associated with quinoline alkaloids and are the alkaloids of mescaline cactus, while benzylisoquinolines are the opium poppy’s papaverine. Morphine alkaloids include narcotics such as morphine (which is one of the best pain relievers available), codeine and thebaine, all from the opium poppy family.

Alkaloid D-tubocurarine – possess a special healing power as it enables muscles to unwind as well as protect them from paralysis. This alkaloid has been used extensively to unwind the muscles of the heart during open heart surgeries and for curing spastic or convulsive paralysis of tetanus venom that causes retrenchment of muscle all over the body.

Purine alkaloids – are medicinally beneficial for extending the effectual life of hormones such as adrenaline. Purine alkaloids are moderate invigorators like coffee (Coffea arabica), tea (Camellia sinensis), yerba mate (Ilex paraguariensis), guarana (Paullinia cupana), and cola (Cola nitida).

Terpenoid alkaloids – are an assortment of compounds that are obtained biosynthetically through different procedures that produce a number of terpenes and steroids which display anti-feedant and anti-fungal features that are normally beneficial for curing hypertension (high blood pressure), neuralgia, and rheumatism.

This article is an example of why we should convince people to conserve the varied flora and fauna in natural ecosystems around the world, for we have yet to learn about all the medicinal benefits the plant kingdom can provide to cure the various ailments plaguing people.

Sources

Albert T. Sneden, PhD, “Natural Products as Medicinally Useful Agents”, Virginia Commonwealth University, 2009.
Herbs 2000, http://www.herbs2000.com/h_menu/tannins.htm, 2009.
“Management Techniques for Pest and Disease Control”, Wales Biomass Centre, Cardiff University, Game Conservancy Ltd., Fordingbridge, UK, 2009.
Sage R.B., Fell D., Tucker K. & Sotherton N.W. “Post hibernation dispersal of three leaf-eating beetles (Coleopteran: Chrysomelidae) colonizing cultivated willows and poplars”, Agricultural and Forest Entomology. 1, 61-70, 1999.
Semere T. & Slater F.M. “The effects of energy grass plantation on biodiversity”, 2005.
Tucker K. & Sage R. “Integrated pest management in short rotation coppice for energy: A growers guide”, 1999.
Wikipedia, the free encyclopedia, 2009.

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Tree of the Seminar
Edited by Len Phillips

'Frans Fontaine' Hornbeam is a beautiful tree for narrow urban sites. It has good disease resistance, dark green leaves, and excellent columnar 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: Carpinus betulus 'Frans Fontaine'
Trade Name: 'Frans Fontaine' Hornbeam
Parentage: Carpinus betulus cultivar
Family: Betulaceae
Year of Introduction: 1990
Family: Betulaceae
Height: 30' - 35'
Spread: 15'
Form: Narrow columnar form does not broaden with age
Bloom Period: April
Flower: Unattractive small catkins
Fruit: ¼" long, mature in early fall
Summer Foliage: Dark green in summer
Autumn Foliage: Yellow in late fall.
Winter Color: Bark provides winter interest
Bark: Dark gray
Habitat: Originally grown in Europe and Asia Minor
Culture: Adapts to most soils, prefers well drained soil and full sun
Hardiness Zone: 5 - 9
Growth Rate: Slow to moderate
Pest Resistance: None serious except loved by beavers for eating
Storm Resistance: Extremely hard wood, heavy and tough
Salt Resistance: Excellent
Planting: B&B in spring
Pruning: Seldom required, but will tolerate heavy pruning for hedge use
Propagating: Cuttings made in July or grafted to C. betulus seedlings
Design Uses: Excellent for screens, hedges, formal landscapes, medium texture
Companions: Will tolerate shade from larger companions
Other Comments: Tough, adaptable, good urban tree, good for screening and narrow sites, average appearance in New England, preferred over species
Available From: Most large nurseries
Photos: J. Frank Schmidt & Son

Tree ring dating, called dendrochronology, is a fascinating science that uses the annual growth rings of long-lived trees as a record of climatic change in a region. To understand how dendrochronology works you must first understand tree rings which are more accurately called growth rings.

Growth Rings
It's fairly common knowledge that you can tell the age of the tree by counting the growth rings. However, look a little closer at each growth ring, and you will see a wider, light-colored area to the inside of a thin dark area. The light-colored area is growth that occurs during the summer months (but is called spring-wood), when sap flows freely through the tree and growth occurs very quickly. Conversely, the darker-colored section occurs during the winter (but is called summer-wood), as the tree's genetic code sends out signals to built up a layer to protect the fresh summer growth. This outer layer of the growth ring works with the cambium layer and bark to protect the tree from the cold of winter. To prepare for the winter months, a tree will pull the majority of its sap from the upper reaches of the tree to help keep it from freezing.

When pioneers built their log homes, they always harvested their trees in the winter, for two reasons.

First, with the sap out of the majority of the tree, less time would be required to "season" the wood before building.
Second, since the bark would need to be stripped from the tree before the log could be used, the log would last longer if the outermost portion of the log was the protective outer growth ring.

If a tree is harvested before spring, the sap is likely out of the tree when it is cut down. This means that the tree is probably a bit easier to kiln dry, and is likely going to be less susceptible to twisting, cupping, bowing or checking, even though it is just as dry as wood harvested in the summer.

Chronological Markers
Absolute dating, the ability to attach a specific chronological date to an object or collection of objects was not available for archaeologists until the 20th century. Only relative dates could be determined with any confidence.
Since the turn of the 20^th century, several methods to measure elapsed time have been discovered that do not use tree growth rings. The first and simplest method of absolute dating is using objects with dates inscribed on them, such as coins, or objects associated with historical events or documents. For example, since each Roman emperor had his own face stamped on coins during his realm, and dates for emperor's realms are known from historical records, the date a coin was minted may be discerned by identifying the emperor depicted.

Dendrochronology
The use of growth ring data to determine chronological dates was first developed in the American southwest by astronomer Andrew Ellicott Douglass. In 1901, Douglass began investigating tree ring growth as an indicator of solar cycles. Douglass believed that solar flares affected climate, and hence the amount of growth a tree might gain in a given year. His research culminated in proving that growth ring width varies with annual rainfall. Not only that, it varies regionally, such that all trees within a specific species and region will show the same relative growth during wet years and dry years. Each tree then, contains a record of rainfall for the length of its life, expressed in density, trace element content, stable isotope composition, and intra-annual growth ring width.

Using local pine trees, Douglass built a 450 year record of the growth ring variability. Clark Wissler, an anthropologist researching Native American groups in the Southwest, recognized the potential for such dating, and brought Douglass fossilized wood from Pueblo ruins that provided ancient ring growth.

Unfortunately, the wood from the Pueblos did not fit into Douglass's record, and over the next 12 years, they searched in vain for a connecting ring pattern. In 1929, they found a charred log near Show Low, Arizona, which connected the two patterns. It was now possible to assign a calendar date to archaeological sites in the American southwest for the past 2000 plus years.

Measurements
Growth ring dating works because the rings are established annually in trees, caused by seasonal changes like temperature and moisture availability. Dendrochronology measures a tree's cambium, the layer of cells that lies between the wood and bark and from which new bark and wood cells originate. Environmental inputs into the cambium include non-chronological changes such as regional climatic variations, which establish recognizable patterns in the rings, encoded as variations in the width of a particular ring, in the wood density or structure, and/or in the chemical composition of the cell walls.

Pros
Determining calendar rates using dendrochronology is a matter of matching known patterns of light and dark rings to those recorded by Douglass and his successors. Dendrochronology has been expanded in the American southwest back to 322 BC, by adding increasingly older archaeological samples to the record. There are dendrochronological records for Europe and the Aegean, and the International Tree Ring Database has contributions from 21 different countries.

Cons
The main drawback to dendrochronology is its reliance on the existence of relatively long-lived vegetation with annual growth rings. Secondly, annual rainfall is a regional climatic event, and so growth ring dates for the southwest are of no use in other regions of the world.

Many growth ring records have been developed over the past 100 years, including an 8,700 year-long bristlecone pine sequence in California and a 10,000 year-long sequence of oak trees in central Europe. Building a chronology of climate change in a region is interesting and undeniably useful to understanding our natural history.

Sources

Baylor, Chris, "How Do Growth Rings Affect Wood Stock?”, About.com Guide, 2009
Hirst, K. Kris, "Tree Rings and Culture”, About.com Guide, 2009

Sometimes called “tree vaults”, tree planting pits are also referred to as “tree coffins,” and with good reason. Trees in concrete-laden urban settings struggle with many stresses that inhibit growth such as limited rooting space, air pollution, road salt, excessive temperature, vehicle impacts, etc. Although planting in tree pits is not ideal, in many cases pits offer the only opportunity for planting trees in a street-scape setting.

Tree pits should be constructed so that a continuous channel of soil under the pavement connects the individual pits and allows greater volumes of soil for root growth and water storage. Raised tree planting areas can likewise be designed to accommodate multiple rather than single trees.

Individual pits can be above, at, or below the surface of the pavement. If they are above, extra provisions must be made for:

supplemental fertilization,
irrigation,
trip hazard warning for pedestrians.

If they are at surface level, plant a ground cover at the time of tree installation to discourage foot traffic over the tree roots.

If the pit soil level will be 2” – 8” below the pavement surface, install an adjustable pit cover or grate that will accommodate trunk growth while not being a trip hazard.

Rooting Space
Unfortunately, planting success in a tree pit often follows what might be called the “Rule of Four”– the roots of a tree with a 4” trunk diameter will fill up a 4’x4’x4’ pit within 4 years. This usually results in a growth slowdown or stoppage and tree death. A soil volume of 5 cubic feet per 1 square foot of crown spread is a recommended minimum.

Research on tree planting practices has yielded new information on reducing stress to urban trees. A planned street or sidewalk reconstruction offers a prime opportunity to build better tree planting sites. The following strategies are the best bets for ensuring tree survival and green streets.

Good Soil
The best method to prepare a site for planting is to remove all urban rubble in a trench between tree pits and refill the pits and trenches with uniform, good quality loam. Soil ingredients should be thoroughly prepared and mixed before planting. The soil type should be consistent throughout the pit and to the outermost location available for root growth. Soils for tree pit design must carefully fit the location. Aeration and water – too much or too little, must be considered.

The CU-Structural Soil™ mix, sometimes called an engineered or load-bearing soil, is an alternative for rubble replacement in pits and under sidewalks. This mix was developed and patented by Cornell University and contains approximately 80% uniform sized stones mixed with about 20% loam and a small amount of material that sticks the soil to the stone. The mixture is designed to preserve large air spaces and ensure oxygen supply to the roots while providing a stable base for pavement.

Amsterdam Tree Soil is a soil mix that will hold water for the tree while allowing for the modest compaction necessary for sidewalks. Amsterdam soil will not meet most engineering compaction standards in the U.S., so it is not a suitable alternative.

Water
A tree in a pit often suffers from oxygen deprivation due to poor drainage. In addition to filling the pit with a uniform soil profile, drainage can be facilitated by a system that will drain excess water from the roots. The pits can be linked with a network of pipes.

The typical tree pit has a volume of only 64 cubic feet. Research has shown that a tree with a 20’ diameter canopy requires 300 cubic feet to have enough water for ten days without rain. Trees in pits should be deeply watered two or three times during backfilling and deep, regular soakings thereafter. The use of pavers can be one way to enable water and oxygen to permeate the soil. Trenches connecting trees can provide additional soil volume.

Citizen volunteers concerned with street tree survival are using an innovative irrigation system in Boston, MA. Used in conjunction with a tree grate, the system consists of a 4” black perforated pipe inside a filter sleeve to keep out silt; a “T” joint; and a 4” round black slotted drain cap. The perforated pipe is laid in a circle just below the soil surface around the root ball, with the “T” joint leading up to the drain cap. Although the cap is protected beneath the grate, it is easily accessible with a hose. Boston’s tree advocate groups now only plant a tree when they have a volunteer committed to watering it. Once a week the volunteer uses a hose to fill the system to overflowing, lets it drain, and then fills it again. The entire system costs about $10 per tree, and it holds up for about three years, long enough to get the young tree established.

Plastic irrigator bags are commercially available products that drain very slowly, so as to provide an effectively deep watering of young trees. A number of communities have had success with these and most report that vandalism has not been a problem despite the visibility of the bags. A scheduled maintenance commitment is necessary to ensure that the bags are filled regularly.

Group Planting
One alternative to using planting pits is to consolidate several trees into one large planting area where several trees can be planted close together. This not only provides a suitable area for root growth, it also encourages tree growth because they grow in groves and forests naturally. Unfortunately, this alternative can not easily be used in a typical city sidewalk and a great deal of creativity on the part of the arborist is necessary to find suitable locations where groves can be planted.

Choose the Right Species
A critical step toward the creation of any sustainable street-scape is to select the right tree for the right place. Only small trees or flood plain species can survive in small spaces. Planting in self-contained tree pits dictates the use of slow growing species that have a relatively small mature size and a tolerance for urban conditions. Near structures, trees with a columnar shape can avoid pruning later. Avoid trees with large surface roots that may damage pavement and trees with dense canopies that block light penetration to the pavement, preventing rapid evaporation of precipitation. Also avoid trees that can litter the pavement with fruit, branches, and large leaves.

Small stature trees for small planting pits
Hedge Maple
Amur Maple
Japanese Maple
Karpick Red Maple
Shadblow
American Redbud
Dogwood
Crabapple
Sourwood
Amanogawa Cherry
Japanese Tee Lilac

Tree Grates
A tree grate serves as a sidewalk-like surface for pedestrian traffic, protecting the soil from compaction and still enabling water to reach the roots. Tree grates have fallen out of favor for street tree plantings because the concentric rings of the grates are seldom cut away as the tree trunk grows. Eventually the grate girdles the trunk.

Standards – Tree grates are available in standard sizes in round, square, or rectangular shapes. The designs are ADA (American with Disabilities Act) compliant with openings no greater than ¼” (0.6cm) and are easily modified to accept up lighting. They can be expanded to not restrict the growth of the trunk.

The two most common mistakes when specifying tree grates are choosing inappropriate sizes and improper installation. If a tree grate is placed directly on the soil instead of suspended on a proper frame, it may cause soil compaction and vertical compression on the roots that will destroy a tree completely. Use tree grates with a minimum 12” (30 cm) opening for the tree and with removable sections that can be broken or cut out to allow for the growth of the tree. Fill the space between the finish grade of the tree and the tree grated with gravel larger than ¼” (0.6cm) to limit the accumulation of debris under the grate while still allowing air and water penetration..

Soak Stone Tree Grate – A new concept coming out of New Zealand consists of a unique porous grate of small colored stones that prevents liter accumulation, assists tree growth and provides an attractive design. It is manufactured in two halves with an anti-skid surface and is virtually maintenance free. It is covered with pebbles that are contained in a galvanized frame that can be powder coated. The grate can be moved to another site once they are no longer needed.

Tree Guards
Tree guards should extend vertically from tree grates and serve to protect trees in highly active areas. Tree guards should be narrow and painted in a similar color to other site furnishings. They are designed to protect trees from harsh weather, vandals, and animals. They are manufactured in two or more pieces and are bolted together for ease of shipping and installation around trees.

Pavers
Instead of tree grates, use bricks, cobblestones, or pavers to create a low-walled area surrounding the planting pit that is 6” – 12” (15 – 30 cm) above sidewalk level. This raised bed encourages pedestrians to walk around and helps limit compaction over the roots closest to the tree. An option is to lay the pavers level with the sidewalk around the tree. Pavers allow air and water can move into the soil through the spaces between the pavers. Pavers are most effective when used in conjunction with structural soils, avoiding the need for a heavily compacted base of stone dust or sand.

Mulch
Organic mulch is normally recommended around trees for water retention and weed prevention. However, it is impractical for street trees set level with sidewalks. Mulch maybe used in a raised planting bed if the sides are high enough to contain it.

Structural Pruning
The pruning goal for a pit-bound tree is to keep it at a manageable size that will help it maintain a sustainable shoot-to-root ratio. Excessive pruning may help limit root growth in areas with small soil volume.

Maintenance
Maintenance on newly planted trees should be planned for at least one year after planting and preferably into the second and third years. Volunteers can be great assistants for watering and for training young trees with structural pruning from the ground. Volunteers are enthusiastic, often protective advocates for public trees, and they are cost-effective labor.

In many communities, planting in pits provides the only opportunity to grow trees. Even though pits are not perfect, sound planting and maintenance practices can go a long way toward compensating for the limiting site factors that they present.

Above Ground Containers
Above ground containers that are decorative and sit on top of a paved surface, come in a wide range of sizes, colors, and materials. The sizes designed for trees range from 90 gallons (44” diameter by 18” high) up to 450 gallons (70” diameter by 30” high) [340 liters (110 cm dia. x 48 cm high) to 1700 liters (180 cm dia. x 75 cm high)]. They can be made of wood, a variety of plastics and metals, ceramic, stone, and precast concrete; for street tree use, as well as for buildings, homes, and offices. They are used indoors as well as outdoors in areas where they have the most visual impacts.

Always plant a tree in the container that will accommodate its root system. Be sure that the container offers ample soil volume and water retention. Plants need to be continually watered in containers and drain holes are necessary to remove any excess water. Container planting means constant watering especially in hot dry spells.

Self-watering planters have a reservoir with a hose-fill attachment. By keeping the reservoir filled, the plants will not run out of water. The design provides continuous soak utilizing capillary action through perforations that expose the soil to the water reservoir. If there are heavy rains, the planters should have built in overflows to eliminate over-watering

Sources

Appleton, Bonnie, "Trees for Parking Lots and Paved Areas", Virginia Tech, Publication Number 430-028, May 1, 2009.
Doherty, Karen, David V. Bloniarz and H. Dennis P. Ryan, "Positively the Pits! Successful Strategies for Sustainable Streetscapes", TCI Magazine - November 2003.
K Accents, website, http://www.kaccents.com
Neely, Dan, and Gary Watson, "The Landscape Below Ground II", International Society of Arboriculture, 1998.
Phillips, Len, “Street-tree Pitfalls”, ArborAge, August/September 2009.
Watson, G. and Dan Neely, "The Landscape Below Ground", International Society of Arboriculture, 1993.

1) Specific trees to assess (i.e. location or selection criteria);

2) Level and details of risk assessment;

3) Type of report (e.g. oral, written) to be developed;

4) The time frame for reporting;

5) To whom the report should be presented.

The arborist shall not be required to perform a higher level of assessment than specified by the scope of work.

Levels of risk assessment
The level and detail of tree risk assessment shall be specified. If defects that cannot be adequately assessed are detected during survey or basic inspection, an advanced assessment should be recommended. One or more of the following inspection levels shall be specified:

Level 1 risk assessment – survey – Level 1 shall be a limited visual assessment of an individual tree or a population of trees to identify specified conditions or defects. Conditions to be identified should include obvious defects. Level 1 assessment shall be from a limited, specified perspective, such as drive-by, walk-by, or aerial patrol. The survey assessment methodology shall be specified. Periodic assessments, monitoring, and follow-up recommendations should be made based on the outcome of the assessment and the objectives.

Level 2 risk assessment – basic – Level 2 assessments shall include a 360-degree, ground-based visual inspection of the tree crown, trunk, above-ground roots, and site conditions around the tree. The use of hand tools, trowels, binoculars, or probes, shall not be precluded from a Level 2 assessment. A mallet or other tool should be used to sound the trunk, root collar, and above ground buttress roots in order to detect large hollows and loose bark. Level 2 shall provide a detailed visual inspection of a tree(s) to detect the conditions specified and tree defects in relation to surrounding targets.

A basic assessment should include the identification of conditions indicating the presence of structural defects including, but not limited to:

Dead, diseased, broken branches, stems, and roots;
Weakly attached branches and codominant stems;
Mechanical damage and cracks into the wood;
Abnormal growth such as swelling, ribs, flat areas, or seams;
Indications of decay and cankers;
Root plate lifting, abnormal trunk flare, lack of trunk flare, soil cracks, grade change, restricted or undermined roots;
Unusual tree architecture including lean, low live crown ratio, poor taper, and crown asymmetry.

Level 2 inspections should be considered annually; more frequently if the species, tree size, tree condition, or other factors indicate a need for a more frequent interval. Scheduling inspections shall be the responsibility of the tree owner. Monitoring and follow-up recommendations should be made based on the outcome of the assessment and the objectives.

Level 3 risk assessment – advanced – Level 3 assessments shall include all Level 2 requirements. Level 3 shall include advanced method(s) to provide more detailed information on tree structural strength, the extent of specific structural defects, conditions, or other factors in relation to a target. Level 3 assessment shall include, but is not limited to, one or more of the following tree assessment techniques:

Aerial assessment of branch or stem defects;
Drilling;
Evaluation of target risk;
Increment boring;
Investigation of tree or site history related to possible or defined defects;
Lean assessment;
Probing;
Pull testing;
Radiation assessment (e.g. radar, x-ray, gamma ray);
Resistance drilling;
Sonic assessment;
Sounding;
Sub-surface root and/or soil assessment.

Tools and work practices that damage the tree beyond the scope of normal work practices shall be avoided.

Target
The arborist should consult with the client to evaluate known and foreseeable targets (static target, dynamic target or movable target) within likely striking distance of the specified tree(s) or tree parts.

Risk Analysis
The analysis of the assessment data should include the following:

Specified objectives;
Tree species;
Tree health;
Site conditions and characteristics;
History;
Past failure patterns;
Local weather patterns;
Risk mitigation.

The type of report (oral, written) required should be specified in the scope of work. Written reports should include:

Identification and location of the specified tree(s);
A description of the methods used;
Tree risk evaluation;
Recommendations for mitigating risk;
Recommendations for monitoring and follow-up.

All recommendations other than removal of the tree should contain an advisory that all potential structure and stability concerns associated with any tree cannot be eliminated. Monitoring and follow-up recommendations should be made based on the objective and the outcome of the mitigation steps.

Owner
It shall be the responsibility of the owner, the owner’s agent, or the controlling authority to determine actions and implement follow-up recommendations, mitigation steps, and future inspections.

Structure Checklist
Visual tree assessments may include, but are not limited to:

1) Dead parts,

2) Weakly attached branches, branch aspect ratio, included bark, multiple branches at one point, epicormic branches and shoots,

3) Codominant stems, included bark,

4) Cracks into or through the wood; ribs, seams,

5) Wood decay, abnormal growth patterns, positive Indicators of decay, cavities and other openings, fungal fruiting structures, carpenter ants,

6) Cankers,

7) Tree architecture, live crown ratio, height to diameter ratio, lean, branch distribution, crown position – dominant, codominant, intermediate, suppressed,

8) Root and root collar, severed, decay, restrictions to growth, girdling, root plate lifting, soil cracks, undermined, broken, basal flare.

Decay assessments may include, but are not limited to:

Sounding for bark separation and wood hollows with mallets,
Probing for decay with increment borer, small diameter drill bits, resistance recording drill,
Sonic measurements, two point sonic devices
Multipoint sonic devices - Picus tomography,
Other methods under development including radar, tree and soil applications, thermograph, x-ray, gamma ray,
Root collar and root inspection,
Aerial inspection,
Pull testing,
Modeling wind pattern and force – Wind Rose,
Interpreting results of advanced assessment,
Weather extremes – wind, snow, and ice levels that trees can withstand,
Stem and branch strength loss/decay formula,
Asymmetric decay,
Guideline for action,
Root loss assessment.

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.

California UFC members will receive credits for this article upon request. After taking the test above, please contact us at: test@on-line-seminars.com, say “Send ___ test score to CaUFC” and we will send your score to them.

Soil Management
By ASC A300 Committee

The ANSI A300 Standards are divided into multiple parts, each focusing on a specific aspect of woody plant management. These standards are used to develop written specifications for work assignments for those who supervise the management of trees, shrubs, and other woody landscape plants. The standard does not apply to agriculture, horticultural production, or silviculture.

This is an excerpt of the draft version for the standard ANSI A300 Part 2– Soil Management, which is currently open for public review. If you have any comments on this proposed Standard, please contact Gordon Mann at gordon@sactree.com

Purpose
To provide standards for developing specifications for soil management, modification, and moisture content.

Implementation
Specifications for soil management should be written and administered by an arborist. Specifications for soil management should include location, objectives, site and soil evaluations, number of soil samples, materials, application method(s), soil loosening method(s), and treatment area.

Safety
This performance standard shall not take precedence over applicable industry safe work practices. Performance shall comply with applicable Federal and State Occupational Safety (OSHA) standards, ANSI Z133, as well as other federal, state, and local regulations.

The sites shall be inspected for hazards prior to implementing any soil management operations within the root zones of trees and woody plants. The location of utilities and other obstructions both below and above ground shall be taken into consideration prior to soil management operations. Utilities and other obstructions include, but are not limited to, gas, electric, communications, sewer, drainage, and signage.

Definitions
available water: Water remaining in the soil after gravitational water held within soil macropores has drained and before the permanent wilting point is reached.
bulk density: Mass of dried soil per unit volume; often used as a measure of soil compaction.
compacted soil: A high density soil lacking structure and porosity characterized by restricted water infiltration and percolation (drainage), and limited root penetration.
drip line: A boundary on the soil surface delineated by the branch spread of a single plant or group of plants.
field capacity: The maximum water content of a soil after drainage, due to the force of gravity.
fill soil: Soil placed over the existing soil surface to raise the finished grade to some specified level.
geotextile fabric: A woven blanket manufactured from synthetic fibers.
gravitational water: Water that drains from larger soil pores (macropores) due to the force of gravity.
hand-digging: Careful soil excavation using ‘hand-tools’ to expose roots for inspection or to determine where mechanical excavation can be done without causing significant root damage or loss.
hydraulic soil excavation: The removal of soil using pressurized water to minimize root damage.
impenetrable layer: Full or partial obstructions such as hardpans, plow pans, rock, abrupt textural changes, or retaining walls that restrict drainage.
infiltration: The entry of water into a soil.
minimally injurious soil excavation: Method to remove soil around woody roots that minimizes bark injury, such as manual, hydraulic, pneumatic, or tunneling.
mulch: A material applied to the soil surface to protect the soil, deter erosion, moderate soil temperature, conserve moisture, inhibit weeds, and improve soil structure.
organic layer: The layer of decomposed and decomposing organic material above the mineral topsoil.
percolation: The movement of free water through the soil profile.
permanent wilting point: The point at which a plant roots can no longer absorb water from the soil.
permeability: The ease with which water penetrates and passes through the soil profile.
pneumatic soil excavation: The removal of soil using pressurized air to minimize root damage.
saturated soil: A soil condition where all of the pores (micro and macropores) are filled with water.
soil aeration: The process by which air in the soil is replaced by air in the atmosphere and carbon dioxide is able to diffuse into the atmosphere, or the process of improving soil porosity.
soil modification: Physically or chemically altering soils to improve conditions
soil structure: Soil classification characteristic of how soil particles clump or bind together (aggregate), creating voids between the aggregates.
soil texture: Soil classification characteristic of the relative size (fineness or coarseness) of soil mineral particles, specifically the proportions of sand, silt, and clay.
soil volume: The volume of soil available to trees and other woody plants for root development.
specifications: A detailed, measurable plan or proposal for performing a work activity or providing a product, usually a written document.
topography: As used in this standard, pertains to the surface of the land – the physical relief or terrain, such as hills, ridges, slopes, swales, drainage, slope and aspect – that influence water movement and drainage, soil depth, soil moisture content, exposure to sunlight, wind, and other factors.
wood-chip mulch: A material placed on the soil surface composed of coarsely ground wood, bark and leaves usually generated by sending tree parts through a wood chipping machine.

Soil Management
Soil management objectives shall be established before the specified work is to begin and shall include, but are not limited to, one or more of the following:

Protecting existing root systems;
Preventing or mitigating soil conditions unfavorable for root growth;
Ensuring plant establishment and long term survival;
Enhancing root function and development;
Promoting plant health, increasing growth and improving appearance;
Managing soil moisture;
Managing diseases;
Inhibiting competitive vegetation;
Reducing soil erosion and compaction;
Enhancing soil biological diversity.

General
Soil management practices should include, but are not limited to, one or more of the following:

Assessing soil conditions;
Mulching;
Tilling (cultivation);
Adding amendments to alter soil conditions;
Fertilization;
Irrigation;
Improving drainage;
Removing fill soil or pavement within the root zones of trees;
Providing adequate soil volume for new planting.

Material safety precautions shall be followed for all products and shall be used in accordance with federal, state, and local regulations. To achieve the defined objective:

Site factors shall be considered, including proximity to waterways, past soil management practices, slope, and irrigation.
Applications of materials to adjust the soil pH shall be considered.
Plant conditions such as disease, insect infestations, and herbicide damage shall be considered.
Soil modification to improve nutrient uptake shall be considered prior to fertilization.

Practices that reduce natural leaf litter accumulation within the root zones of plants should be avoided.

Soil Modification
Soil modification objectives shall include, but are not limited to, one or more of the following:

Protect existing roots;
Enhance root development;
Maintain tree health.

Soil modification practices shall include one of more of the following:

Evaluating site soil conditions;
Managing soil organic matter content;
Prevention and mitigation of soil compaction.

Evaluating Site and Soil
Site and soil evaluation objectives shall be established and the following items should be considered:

Site topography – surface and subsurface drainage;
Soil drainage (infiltration and percolation);
Soil texture;
Soil profile;
Soil structure (bulk density);
Soil depth;
Presence of impermeable layers and height of water table;
Organic matter levels.

Soil testing as well as soil and site physical characteristics should be assessed prior to designing, planting, and/or developing management plans for landscapes. The number of samples to be collected should be specified and should be representative of the site.

Organic Matter
Soil organic matter management objectives shall be established including but are not limited to, one or more of the following:

Maintain soil organic matter at an adequate level for the plant species at the site. If soil organic matter content is low, organic materials should be incorporated into the soil or applied to the surface as mulch.
When organic matter is incorporated into the soil, compost should be used.

Compaction
Objectives for prevention of soil compaction shall be established including but are not limited to, one or more of the following:

Maintain or improve soil aeration;
Maintain or increase water penetration (infiltration rate) and percolation;
Maintain or enhance water-holding capacity and drainage;
Maintain or improve ease of root penetration;
Maintain or reduce surface runoff and soil erosion.

Methods to mitigate compacted soils shall be specified including but are not limited to:

Mulching;
Incorporation of soil amendments;
Mechanical loosening (cultivation);
Loosening using high pressure air.

Measures should be taken to prevent or minimize soil compaction while working within the root zones of trees and woody plants or where landscapes are planned. Activities on wet soils should be avoided and preventative actions shall be taken to avoid compaction. Soils with surface compaction in areas where landscapes are planned should be amended with organic matter following mechanical loosening to the depth of soil compaction. Mulching should be considered an effective long term means to treat compacted soil within the root zones of trees and woody plants.

Application of Mulch
The objectives of mulching shall be established including but are not limited to one or more of the following:

Inhibit weed growth;
Conserving soil moisture;
Moderating soil temperature extremes;
Preventing and alleviating soil compaction;
Preventing soil erosion and surface crusting;
Improving the soil structure and fertility;
Encouraging beneficial soil microorganisms;
Inhibiting certain root pathogens;
Increasing root growth and plant vigor.

The types of mulch and methods of application shall be specified to meet the objective. When selecting the type of mulch, consideration should be given to tree species, soil conditions, irrigation practices, and pathogenic fungi. Fresh or partially composted coarse wood-chip mulch (greater than ¾ inch average wood particle size) from trees should be preferred when the objective is to improve soil structure and enhance soil biological activity.

Fresh wood-chip mulch that is known to cause an allelopathic response in the plants being mulched, or contaminated by a transmittable disease, or contain seeds of undesirable plant species, should be avoided. The ignitability of mulches shall be considered. Neither impervious plastic sheeting nor pervious fabric or sheeting should be used under the mulch when the objective is to improve soil structure and increase organic matter content. Mulch shall not be placed against tree trunks. Mulch should be applied over as much of the root zone as practical and applied and maintained at a depth of 2-4 inches (5-10 cm).

Soil Amendments
All soil amendments specified should be appropriate for the chemical and physical characteristics of the site soil and to meet the objective. When re-compaction is a concern, structural amendments, based on soil texture, shall be specified to meet the objectives. Non-composted woody materials shall be avoided when incorporating into the soil. Composts, when used as soil amendments, should be tested by a qualified lab for chemical properties, such as pH and salt index. Soil amendments should be incorporated into the soil after mechanical loosening of the soils has been completed and they should be incorporated throughout the layer of compacted soil. Sand should not be considered a soil amendment for clayey soils unless it will exceed 50% of the soil volume following amendment. Gypsum should not be considered an effective amendment for mitigation of soil compaction for soils with high calcium content or excessive sodium (sodium adsorption ratio > 6).

Mechanical Loosening
Compacted soil should be mechanically loosened before adding topsoil. The depth of the compacted layer to be loosened shall be specified. Compacted soils should be moist before being loosened using pneumatic excavation tools (the preferred method to loosen compacted soil). Moisture content of compacted soil should be less than field capacity before being tilled. Under existing plants, compacted soils should be loosened using the least injurious method to meet the objective. When mechanical loosening of the soil is impractical, organic mulch should be applied to mitigate the compaction in time. Remediation includes loosening, amending, and /or replacing.

Moisture Practices
The objectives of managing soil moisture shall be established to include, but are not limited to, one or more of the following:

Preventing environmental stress on plants;
Managing disease problems;
Promoting plant growth;
Mitigating plant damage from human activity;
Improving plant aesthetics;
Increasing fire-resistance;
Preventing excess water from collecting within the root zones of plants;
Improving soil aeration;
Managing subsurface water flow;
Managing surface water flow.

Measures to manage soil moisture and mitigate drainage problems should include one or more of the following:

Reduction of soil compaction;
Mitigation of impermeable layers (deep cultivation);
Excavation, swales, ditches;
Installation of drains, sumps.

Soil drainage improvement should be considered most practical when done as a treatment prior to plant installation. Where drainage is restricted, and it is not practical to mitigate the conditions, species tolerant of wet soils should be selected. When improving drainage is not practical, planting on soil mounds or large berms should also be considered to improve soil aeration in plant root zones.

Drains should be installed through or behind retaining walls to prevent water from impounding behind the walls. Drain systems shall have sufficient slope to achieve the objective. Planting containers shall have adequate drainage or facility to remove excess water.

Impenetrable Layers
Impenetrable layers that restrict drainage, limit aeration, or impound water should be mitigated near the surface by sub-soiling or soil ripping prior to planting. Auguring holes through impermeable layers around existing plants, and areas that can not be disrupted by conventional means should be considered to improve drainage.

Surface drains (swales, ditches, culverts, berms, etc.) should be considered to prevent water from collecting around trees or in landscaped areas if drainage is slow or impeded.

Subsurface drainage should be installed in sites where drainage is slow, the water table is close to the surface, or water is impounded by retaining walls, foundations, etc. Subsurface drains should be installed to an adequate depth to meet the objective. The subsurface drain method (French drains, perforated pipes, etc.) and design shall be specified. French drains should be excavated to the depth needed to ensure favorable root zone conditions and be filled with coarse, uniform-sized gravel. Filter-fabric should be installed around perforated pipe to prevent infiltration of soil material.

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.

California UFC members will receive credits for this article upon request. After taking the test above, please contact us at: test@on-line-seminars.com, say “Send ___ test score to CaUFC” and we will send your score to them as well as the ISA.

Fertilization
By ASC A300 Committee

The ANSI A300 Standards are divided into multiple parts, each focusing on a specific aspect of woody plant management. These standards are used to develop written specifications for work assignments for those who supervise the management of trees, shrubs, and other woody landscape plants. The standard does not apply to agriculture, horticultural production, or silviculture.

This is an excerpt of the draft version for the standard ANSI A300 Part 2– Fertilization, which is currently open for public review. If you have any comments on this proposed Standard, please contact Gordon Mann at gordon@sactree.com

Purpose
To provide standards for developing specifications for fertilization.

Reason for fertilization
The reason for fertilization is to supply nutrients determined to be deficient to achieve a clearly defined plant management objective. That objective should be accomplished in the manner most beneficial to the plant and the environment.

Implementation
Specifications for fertilization should be written and administered by an arborist. Specifications for fertilization should include location of plants, objectives, materials, rate, application method(s), treatment area, and timing.

Definitions
buffering capacity: The ability of the soil to maintain or resist a change in pH.
fertilization: The application of fertilizer to the soil or plant.
fertilizer: A substance containing one or more nutrients to be added to a plant or surrounding soil to supplement the supply of essential elements.
fertilizer analysis: The composition of a fertilizer expressed as a percentage by weight of total nitrogen (N), available phosphoric acid (P₂O₅), soluble potash (K₂O), and other nutrients.
fertilizer ratio: The ratio of total nitrogen (N), available phosphoric acid (P₂O₅), and soluble potash (K₂O); e.g., the ratio of a 30-10-10 fertilizer is 3:1:1.
implant: A capsule or other device permanently inserted into the xylem.
nutrient: Element or compound required for growth, reproduction or development of a plant.
macronutrient: Nutrient required in relatively large amounts by plants, such as nitrogen (N), phosphorus (P), potassium (K), and sulfur (S).
secondary nutrient: Nutrient required in moderate amounts by plants, such as calcium (Ca) and magnesium (Mg).
micronutrient: Nutrient required in relatively small amounts by plants, such as iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and boron (B).
organic fertilizer: A carbon-based fertilizer that releases essential plant nutrients upon breakdown.
quick-release fertilizer: A fertilizer that is immediately available to the plant.
salt index: A measure of the salt concentration that fertilizer produces in the soil solution. The higher the salt index, the more likely that plant damage will occur.
slow-release fertilizer: A fertilizer containing plant nutrients in a form that delays availability for plant uptake and use after application, or that extends availability to the plant.
soil pH: The relative acidity or alkalinity of soil; the negative log of the hydrogen ion concentration.
soil salinity: The measure of the concentration of mineral ions dissolved in soil solution (water).
specifications: A detailed, measurable plan or proposal for performing a work activity or providing a product, usually a written document.
subsurface application: The application of dry or liquid fertilizer below the soil surface.
surface application: The application of dry or liquid fertilizer to the soil surface, mulch or ground cover.
trunk injection: The process of injecting a liquid into the plant.
water-insoluble nitrogen (WIN): Nitrogen not readily soluble in cold water

Fertilization Practices
Fertilization objectives shall be established prior to beginning any fertilization operation including but not limited to, one or more of the following:

Ensuring plant establishment and long term survival;
Enhancing root function and development;
Promoting plant health, increasing growth and improving appearance;
Enhancing soil biological diversity.

Soil and/or foliar nutrient analysis should be used to determine the need for, type, and rate of fertilizer, as well as timing, method, and location of application treatment area. Soil pH shall be considered when selecting the fertilizer. New transplants and plants sensitive to fertilizer salt should only be fertilized with a slow-release fertilizer.

pH Adjustment
The objectives for adjusting soil pH shall be established. Soil pH in landscapes with recognized problems should be monitored and treated periodically to meet the objective. When pH adjustments are specified for new plantings, they should be performed prior to plant installation. Elemental sulfur or sulfur-containing compounds should be the preferred material to lower pH. Lime (calcium carbonate) or dolomite (calcium magnesium carbonate) should be the preferred material to raise pH. The material selected to adjust pH should be incorporated or injected into the upper 2 to 4 inches of the soil or to a depth that meets the objective. Adjusting pH in calcareous soil, those containing free calcium carbonate, should be considered impractical.

Types and Rates of Fertilizer
Fertilizer ratio formulation should be adjusted based on objectives, condition and age of the plant, local knowledge, nutrient analysis, site conditions, and/or species. In the absence of soil and/or foliar nutrient analysis, fertilizers with higher ratios of P₂O₅ and K₂O should be avoided with the exception of palms. The amount of water insoluble nitrogen (WIN) shall be considered. Slow-release fertilizers with a minimum 50% WIN should be preferred due to site considerations and plant sensitivity. Fertilizers with a salt index of less than 50 should be preferred. Slow-release fertilizers should be applied at rates between 2 and 4 pounds of actual nitrogen per 1000 ft² (1 to 2 kg N/100 m²) and should not exceed 6 pounds of actual nitrogen per 1000 ft²(2.9 kg N/100 m²) within 12 months. Quick-release fertilizers should be applied at rates between 1 and 2 pounds of actual nitrogen per 1000 ft² (0.5 to 1 kg N/100 m²) per application and shall not exceed 4 pounds actual nitrogen per 1000 ft² (2 kg N/100 m²) every 12 months.

Treatment Area
The fertilization treatment area shall be defined prior to application with consideration given to root accessibility, root location, fertilization objectives, plant species, and site considerations. For most trees and shrubs, the fertilization treatment area should be from near the trunk to near or just beyond the drip line. Inaccessible surfaces shall not be included in the rate calculation. For fastigiate trees and unusual situations, the method for determining the fertilization treatment radius should be calculated by multiplying the plant’s stem diameter at 4½ feet (1.4 m) above ground, measured in inches (cm), by 1 to 1½ (0.12 to 0.18) to determine the radius, expressed in feet (m), from the trunk of the plant. For example, a 15-inch (38.1 cm) DSH (DBH) tree would have a fertilization area radius of 15 to 23 feet (4.6 to 6.9 m).

Application
Where turf or ground covers exist, subsurface fertilization should be the preferred method of fertilization. Precipitation and irrigation methods should be considered. Fertilizer shall be uniformly distributed within the treatment area. Surface applied fertilizers shall be watered in. The watering-in period should be specified based on the objective and the material used. Surface application shall not be made where surface runoff is likely to occur.

Dry Fertilization
Damage to the buttress roots should be avoided. Holes shall be evenly spaced within the treatment area. Hole depth, diameter, and spacing shall be specified. Holes should be 2 to 4 inches (5 to 10 cm) in diameter, spaced 12 to 36 inches (30 to 91 cm) apart, and 4 to 8 (10 to 20 cm) inches deep. The fertilizer shall be evenly distributed among the holes. Fertilizer should be deeper than 2 inches (5 cm) from the soil surface.

Liquid Fertilizer Injection
Damage to the buttress roots should be avoided. Injection sites shall be evenly spaced within the treatment area. Injection site spacing and depth shall be specified. Injection sites should be 12 to 36 inches (30 to 91 cm) apart, and 4 to 8 inches (10 to 20 cm) deep, not to exceed 12 inches (30 cm) deep.

Alternative Techniques
All products shall be used in accordance with manufacturers’ recommendations. Foliar applications, trunk injections, and implants shall only be used when soil application of fertilizer is impractical or ineffective in achieving fertilization objectives. The fertilizer shall be formulated for the application method. Water pH, salinity, and hardness should be considered. When applying foliar fertilizer, the fertilizer solution should be sprayed to thoroughly cover the foliage at the proper stage of growth to achieve fertilization objectives.

Injections and implants
Timing of injection/implant application should be at the proper growth stage to achieve fertilization objectives. Products should be applied in the root flare or as low as practical in the trunk. Holes shall be made as small and shallow as practical. Application intervals should be timed to optimize results with minimal negative impact. Small diameter trees and drought-stressed trees should not be treated with injections or implants. If a drill is used to create injection/implant sites, sharp bits shall be used.

Soil Sampling Guidelines
The number of samples taken may depend on the size of the site, the variability of soils at the site, history, and the level of accuracy needed. When soil conditions appear variable, planting sites may be divided into sampling units. Samples taken at the 0 to 6-inch layer are typically done to assess chemical properties of the soil. Samples taken at deeper measurements are typically done to identify changes in profile (textural changes), obstructions to drainage, and propensity for root development.

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Research Briefs
Edited by Len Phillips

California Elm Trial
Greg McPherson, Larry Costello, James Harding, Steve Dreistadt, Mary Louise Flint and Skip Mezger
In 2005, 14 cultivars of elm trees were planted at UC Davis. The planting was part of the National Elm Trial, with trees provided by J.F. Schmidt & Son and Princeton nurseries to 18 locations across the nation. The purpose of the study is to determine the growth and horticultural performance of commercially available Dutch elm disease resistant cultivars in various climate regimes. This initial report summarizes data collected on tree growth, habit, pruning requirements, and pest and disease resistance.

Five trees from each of the 14 cultivars were planted. They are:
Ulmus propinqua ‘JFS-Bieberich’ Emerald Sunshine® Elm
Ulmus parvifolia ‘Emer II’ Allee® Elm
Ulmus ‘Frontier’ Frontier Elm
Ulmus ‘Homestead’ Homestead Elm
Ulmus ‘Morton Glossy’ Triumph™ Elm
Ulmus ‘Morton Plainsman’ Vanguard™ Elm
Ulmus ‘Morton Red Tip’ Danada Charm™ Elm
Ulmus ‘Morton Stalwart’ Commendation™ Elm
Ulmus ‘Morton’ Accolade® Elm
Ulmus ‘New Horizon’ PP8684 New Horizon Elm
Ulmus ‘Patriot’ Patriot Elm
Ulmus ‘Pioneer’ Pioneer Elm
Ulmus wilsoniana ‘Prospector’ Prospector Elm
Ulmus americana ‘Valley Forge’ Valley Forge Elm
Ulmus americana ‘Princeton’ Princeton Elm
Ulmus ‘New Harmony’ New Harmony Elm

During the first growing season one Ulmus ‘Frontier’ and all of the Ulmus parvifolia ‘Emer II’ (Allee elm) died.
Cultivars exhibiting the greatest average annual DBH growth were New Horizon, Vanguard, and Homestead. Slowest growing cultivars in DBH were Emerald Sunshine, Frontier, and Accolade.
Frontier, Emerald Sunshine, and Accolade were evaluated as having a relatively low pruning requirement, while Valley Forge, Vanguard, Pioneer and Princeton were considered to have a relatively high requirement.
We observed no Dutch elm disease or bark beetle boring damage on any cultivars. Elm leaf beetle (ELB) has been the only significant invertebrate problem. About one-half of the study cultivars experienced 30% or greater leaf-chewing damage. Leaf curling aphids (Eriosoma sp.) have infested only the American elm selections Princeton and Valley Forge.

Western Arborist Vol. 35 No. 3 Fall 2009

Control of Oak Powdery Mildew
Glynn Percival and Ian Haynes
A field trial was conducted using established English oak (Quercus robur) to assess the efficacy of four commercially available systemic-inducing resistance (SIR) compounds (salicylic acid, potassium phosphite, harpin protein, betaine) applied as a single therapeutic spray treatment against the foliar pathogen oak powdery mildew (Microsphaera alphitoides). In addition, a comparative evaluation of a conventional spray program (3 week spray intervals) for powdery mildew control was conducted using the fungicide penconazole which appear to posses marginal SIR properties.

The SIR-inducing compound containing betaine and a single spray treatment of penconazole had no significant influence on disease severity and specific activity of peroxidase and superoxide dismutase. Salicylic acid and potassium phosphite had no significant long-term effect on disease severity; although a short-term reduction in disease severity was recorded that was associated with enhanced leaf peroxidase and superoxide dismutase activity. A single therapeutic application of the harpin protein significantly reduced disease severity of powdery mildew. Only repeat spray applications of penconazole significantly reduced disease severity of oak powdery mildew.

Arboriculture & Urban Forestry, Vol. 34, No. 5 September 2008

Technology for Early Sex Determination of Ginkgo biloba
Vincent Echenard, François Lefort, Gautier Calmin, Robert Perroulaz, and Lassaad Belhahri
Random amplified polymorphic DNA (RAPD) technique with male associated decamer primer S1478 was used to amplify DNA from 72 leaf samples collected from Ginkgo biloba trees with known sexual determinism. This marker was found to be male-specific and was lacking in all female plants. Automated random polymorphic DNA analysis (ARPA), a new automated technology developed in the frame of this work, proved highly effective in distinguishing males and females with 100% efficiency and successful in male and female discrimination from a collection of young seedlings derived from a sexual cross. Our findings provide unambiguous evidence that ARPA combined with the male-associated decamer primer S1478 could be considered an efficient, rapid, and easy method to make an early sex determination in Ginkgo biloba.

Arboriculture & Urban Forestry Vol. 34, No. 5 September 2008

Efficacy of Foliar Applications in Reducing Populations of Hemlock Scale
Michael Raupp, Robert Ahern, Brad Onken, Richard Reardon, Stacey Bealmear, Joseph Doccola, Paul Wolfe II, and Peter Becker
We examined the efficacy of two approaches for controlling elongate hemlock scale on eastern hemlocks in an arboretum.

One approach relied on foliar applications of an insect growth regulator, pyriproxyfen, and horticultural spray oil when crawlers were abundant.
The second approach evaluated soil drenches and trunk injections of the systemic insecticides imidacloprid, dinotefuron, and acephate.

Foliar applications of pyriproxyfen and horticultural oil provided superior levels of control of elongate hemlock scale compared with soil drenches, trunk injections, or implants of insecticides in the year that applications were made. After foliar sprays, population reductions were rapid and, in the case of pyriproxyfen, lasted into the second growing season. By the third year, significant differences in elongate hemlock scale populations were no longer found among trees treated with insecticides and those that were not. Imidacloprid applied as a soil drench had limited efficacy in reducing populations of elongate hemlock scale on one date in the first season. Acephate implants and trunk injections of dinotefuron did not reduce the abundance of elongate hemlock scale relative to untreated trees. Arborists can achieve high levels of control of elongate hemlock scale with foliar sprays of pyriproxyfen or horticultural oil applied when crawlers are abundant in spring.

Arboriculture & Urban Forestry Vol.34, No. 5 September 2008

Seemingly healthy limbs up to a yard or meter in diameter occasionally break out of mature trees during or following hot calm summer afternoons or during calm weather following a heavy summer rain which ends a period of soil dryness. This type of limb failure occurs on both native and planted trees as well as in irrigated and unirrigated landscapes. People have been seriously injured and property damaged by falling branches. The failure of the top forty feet of a mature Eucalyptus globus in Los Angeles in 1977 seriously crippled a child and resulted in an out-of-court settlement of $1,625,000.

Trees Affected
Limb failure has been reported on species of 19 genera. The phenomenon was first reported on Quercus lobata in the coastal mountain ranges of central California. Young and vigorous trees of susceptible species seem to be less prone to branch failure while over-mature and senescent trees may shed branches repeatedly.

Most commonly, breakage occurs 3 to 14 feet (1 to 4m) from the branch attachment on long limbs that extend to or beyond the tree canopy. Sometimes a branch may fail at its attachment. Less frequently, the main leader or the entire top may fail.

No outward appearance has been associated with impending branch failure. The wood at many breaks appears sound while some or much of the wood at other breaks may be decayed or short and at right angles to the axis of the branch. Decayed wood may predispose branches to the possibility of failure, but does not account for failure occurring under the conditions that it does.

This phenomenon was thought to be confined to times of high temperature in arid regions, such as Australia, South Africa, and southwestern United States, because no one could be found who was familiar with this problem in the midwestern or eastern United States. However, summer branch drop has been reported in England and is serious enough for the Royal Botanic Garden at Kew to post a large sign at each entrance warning visitors that "The older trees; particularly beech and elm, are liable to shed large branches without warning." There have also been reports of branches dropping out of American elms. Others report that sometimes there are defects associated with the failures, and sometimes not. A lack of taper was often associated with the failure. The other factor often noted was a change in direction on the limb.

Possible Explanations
Limb failure on hot afternoons is an anomaly since tree trunks normally shrink in the afternoons. However, there are reports of limbs rising as well as shrinking indicating that transpiration has exceeded water uptake and that limbs are lighter in the afternoon. This is further borne out since most of the breaks are relatively dry. This would be due to moisture tension in the xylem drawing water into the wood on each side of the break.

However, the opposite is often the case. After a break, water has been observed "flowing" from both sides of a fracture. Many report that the limb "exploded" and dropped quickly with no warning.

There are also cases of limb failure late in the season when the hot sun broils and steams the sap. If an ax were struck into a mature Quercus lobata hisses could be heard like a legion of little safety valves. Sometimes, limbs most unaccountably, are said to burst with a loud explosion and strong limbs that had withstood centuries of storms, in the calm airs of late summer and early autumn, crash unexpectedly down, the fracture not disclosing any cause of weakness.

These observations indicated the xylem to be under pressure. Two possibilities could account for this pressure:

Wetwood bacteria have created gas pressures up to 60 psi (4.2 kg/cm2) in elm trunks. Such infections are common in several species subject to limb breakage.
Under calm conditions, transpiration may be greatly reduced due to high humidity within the tree canopies. Root pressure could then increase the moisture content of branches, thereby increasing their weight and internal sap pressure.

Another theory tied to calm weather would be due to reduced high humidity in tree canopy. Because the reduced flow of water in the xylem would allow the branch temperature to increase, this in turn could increase the production of ethylene and other substances. These could begin to weaken the cell wall cementation. This increased weakening, coupled with the increased weight of a limb due to increasing leaf surface and fruit, and reduced transpiration, could result in branch failure. If wood actually weakens under hot, calm, conditions, the process must be reversible or new wood must form rapidly enough to strengthen branches in order for them to withstand the increased weight of rain on the foliage and the strain of wind storms that may follow.

Suggested precautions
Warn people of potential hazard or rope off areas near hazardous trees as was done at Kew. This would be most important from late spring to early fall.

In areas to be frequented by people, do not plant species known to be susceptible to this problem.
On mature trees, shorten and lighten long horizontal branches and open up the tree so humidity is less likely to build up.
Keep trees vigorous and healthy. However, this may be self defeating since potentially susceptible branches would become longer and heavier, but hopefully stronger.
Inspect susceptible trees for externally visible defects, removing low-vigor limbs that have decay or cavities. If the entire tree shows signs of decay and low vigor on all the limbs, strongly recommend removing the tree.

Species most often reported in Britain to be susceptible to summer branch drop.
Quercus spp.
Populus spp.
Salix spp.
Ulmus procera
Castanea sativa
Fagus sylvatica
Fraxinus excelsior
Aesculus hippocastanum

Genera most often reported in California to be susceptible to summer branch drop.
Eucalyptus
Quercus
Ulmus
Pinus
Cedrus
Fraxinus
Platanus

Species reported in California to be susceptible to summer branch drop.
Ailanthus altissima
Erythrina caffra
Ficus microcarpa
Olea europaea
Grevillea robusta
Sequoiadendron giganteum
Sophora japonica

Source
Journal of Arboriculture, 9(4): 113

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.

California UFC members will receive credits for this article upon request. After taking the test above, please contact us at: test@on-line-seminars.com, say “Send ___ test score to CaUFC” and we will send your score to them as well as the ISA.

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