Archive #27 from Online Seminars for Municipal Arborists (on-line-seminars.com) July/August 2009
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 #27

This page will be removed on September 1, 2010

Wildlife Habitat 
By Cynthia Orlando

Not all arborists may be aware of the contribution their work can make to the larger landscape in terms of ecosystem functions and processes. Usually when we think of wildlife habitat we think of animals that make their homes in national forest ecosystems. As rural forests make way for urban growth, city parks and remnant forests are becoming more critical to meeting habitat needs of local wildlife populations such as small mammals and birds.

Most arborists are in a unique position to notice how birds and wildlife use different habitats. This type of observational skill is of real value to leaving a wildlife legacy. But how often do we really remember to think about our activities and work projects in association with bird or wildlife implications?

Maybe you're wondering what kinds of wildlife are likely to be found living in, or nearby, our urban communities. They range from bear and deer to small mammals and amphibians. Most common species include birds, especially migratory varieties, and birds of prey, like hawks, owls, and eagles. Amphibians include frogs and salamanders, and many small mammals including deer mice, voles, tree squirrels, ground squirrels, chipmunks, bats, opossums, and moles.

Conserving habitat in new construction areas

Let's say your work as an arborist takes you into areas where new construction is taking place. Construction activities remove natural habitat components so that the needs of some native birds and animals are no longer satisfied. Most developed and constructed sites result in conditions acceptable to species such as sparrows, pigeons, and raccoons, and compared to natural sites, accommodate fewer native species. Thus they lower native biological diversity.

The effects to species that are threatened or endangered can be even worse. Construction activities can remove habitat and result in animals abandoning the area, thereby eliminating these species both from the site and from adjacent areas.

Habitat Requirements

Conserving the widest diversity of wildlife habitat requirements is a helpful first step.

Food - Plants are a primary source of energy and are the building blocks of large, complex food webs in any environment. Their twigs, leaves, bark, fruits, seeds, nuts, and roots are eaten by animals, birds and insects that in turn are eaten by larger animals. Arborists who work to maintain the greatest diversity of native plants such as groundcover, small and tall shrubs, understory and overstory trees will be leaving the site characteristics suitable to meet the food requirements of wildlife.

Cover - Since birds and wildlife need protection from weather and predators, having diverse types of cover on a site is also important. A combination of native conifers and deciduous trees and shrubs including perennial and annual plants with summer and fall fruits and flowers is optimal. Also, a mixture of vegetation reduces the possibility of losing all the plants to disease or insects.

Because each tier creates its own niche, providing different layers of vegetation (canopy, understory, shrub layer, herbaceous layer, and the floor) are helpful. Again, striving to leave a diversity of plants, as well as dead or dying trees, stumps, and underground burrows, helps meet the habitat needs of wildlife in developed areas like construction sites.

Water - Fresh water, essential for most wildlife within a construction site can be used by wildlife living in the entire neighborhood. Leaving a travel corridor from uplands to existing water supplies like ponds or streams near the site will allow access by many species. These buffers also filter nutrient-laden runoff from adjacent land to preserve and improve water quality.

Habitat Conservation

Perhaps your arborist duties take you into a city's natural areas or its open spaces. Maybe you've been called upon to make recommendations about tree health, tree retention, or tree planting. All over the world, urban parks play a role in biodiversity. But this increasing urbanization results in "fragmenting" forest habitat into smaller, more isolated tracts.

When this happens, the individual stands of trees have less "interior" habitat and are more prone to "edge effects" like changes in micro-climate such as drier conditions or are subject to more extreme temperature changes. Research shows this fragmentation is a primary factor to the loss of wildlife habitat, with migratory bird species some of the most adversely affected.

Again, consolidating open space set-asides and providing corridors that link habitat patches will facilitate wildlife movement. In urban areas, these landscape links are often called "greenways". In fact, because of the rapid growth of urban areas in many places, governments will often provide detailed guidelines for developments next to streams and guidelines for integrating development and greenways. Within these guidelines, a setback distance from the top of the bank is considered the minimum amount of land to be left undeveloped.

A word of caution: remember that narrow bands of remnant forest are often prone to windfall, and should be avoided in highly populated areas.

As an arborist, you may encounter more rural situations where the urban fringe site you are working in is located next to lands managed for grazing or agriculture. Incorporating clumps of native plants, grasses and forbs in these areas can provide quality habitat for wild turkey and other animals.

A Word about Street Trees

While this article is mainly focused on actions arborists can take to conserve habitat in urban fringe areas, a brief mention about street tree composition is also warranted. Biological diversity is a key to sustainability in our urban forests. To avoid catastrophic losses and pest outbreaks, look at the makeup of the street trees; aim for proper diversification levels of no more than 30% of any one family, 20% of one genus, or 10% of one species.

Recognizing and Preserving Wildlife Trees

When thinking about the habitat characteristics of our urban forests, arborists need to better understand which trees and what characteristics are most suitable for present and future wildlife needs. Animal species that use trees for habitat can be sorted into 5 basic categories:

1. Primary cavity excavators - Examples include woodpeckers, flickers, and nuthatches that make and use new cavities every year.

2. Secondary cavity users - Owls, bluebirds and wood ducks, and raccoons, martens, and deer mice, are species which cannot excavate cavities by themselves, but use abandoned holes to nest and raise young.

3. Open nesters - Larger birds like eagles or osprey can use either dead or live trees, but they usually prefer trees with a broken top or flat crown to support their nest and provide a good view of the area.

4. Other mammals - Small mammals like bats, flying squirrels or mice look for shelter and nesting places under loose bark and other small cavities.

    5.   Amphibians - Frogs and salamanders use dead and dying trees for
          habitat, especially once the wood is in an advanced stage of decay.

In general, decaying trees are also an important food source at all levels of the food chain.

Protecting and Creating Wildlife Trees

If you see raptors such as eagles, osprey, or herons nesting in an area, the nest trees might need to be specially designated as wildlife trees. If dead or dying trees are determined to present a high enough hazard to warrant removal, some of the cover requirements they provided can be maintained by placing bird houses in the area.

You can also create the wildlife trees needed by birds like woodpeckers for nesting or perching by selecting trees too tall and unstable to retain. Cut them to a height where they won't be a hazard to people or nearby developments when they eventually fall over. Then roughen up the top or have it notched to encourage nest building. Careful extraction of the tree tops, coupled with retention or replanting of understory trees and plants, can help provide for a wide variety of future wildlife habitat needs.

To help conserve or reestablish habitat:

 Take a look at the regional landscape patterns,

 Make an assessment of other land managers,

 Share information and resources,

 Devise a plan that will have the greatest impact for wildlife.

Source

This was originally published by the Oregon Department of Forestry Urban and Community Forestry Assistance Program

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.

CaUFC credits for this article will be awarded 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.

Using Plants as a Sound Barrier
Edited by Len Phillips

Plants are often promoted for use to reduce or attenuate noise from nearby highways or other sources. Plants have the ability to absorb and scatter sound waves; they also can mask sound with the movement of their leaves. The mix of plants is important because different types of leaves reduce different types of noises. How much noise control they provide depends on the intensity, frequency and direction of the sound, and the location, height, width and density of the planting. However, the effectiveness of trees, shrubs, and ground-covers as noise reducers is still subject to some debate.

Plant Specifications

A great deal of research has been conducted over the years investigating the use of plants for street and highway noise reduction. Various results have been compiled. In general, the following criteria should be considered when proposing trees and other plants for sound reduction.

• Tall and dense plantings in buffer strips (multiple layers) that are thick enough to be visually opaque will provide some noise attenuation in the range of 3 - 10 decibels (dba) per 100 feet of buffer width. The buffer strips should have mixed broadleaf plantings at least 25 feet thick and conifers 50 to 100 feet thick to be effective.

• Deciduous plants do not provide a year round visual barrier or protection from noise. The loss of leaves changes the whole character of the plant for any noise attenuation. Evergreens are more effective for year-round screening and noise reduction.

• Shrubs should be planted in front of the trees to help provide the desired density of growth close to the ground.

• Plants need to be planted as close together as practical in order to try to form a continuous dense barrier.

• Varying growth rates from one plant to another and from one species to another can create situations where the plants may not grow together to produce a dense barrier.

• Plants need to be planted as close to the noise source as possible rather than being planted close to the noise receptor area. The U.S. Department of Transportation has recognized that the principal effect of planting for noise reduction is psychological in nature. By removing the noise source from view, the noise awareness or annoyance can be reduced in the mind of the viewer.

If plants are used, sufficient growth time must be allowed for the plants to attain their optimal height and density. Since most plants are planted in smaller sizes for ease of installation and reduced plant material costs, creating an effective plant screen can take many years before the plants grow dense enough to provide the desired physical barrier.

Noise Barriers

• To be effective, any noise barrier must be solid since sound waves will reflect and be redirected from a solid surface.

• Sound waves can also bend around and over barriers.

• Plants will have a minimal effectiveness on the sound waves due to their general open trunk, branch, and varying leaf structures.

• Many barriers use a combination of plants and solid barriers, or solid barriers alone.

• In certain situations, water features can be used to mask the street sounds, but not eliminate them.

The best way to reduce noise is to establish a soil berm for the plantings:

• Large mounds of soil thickly planted, as described above, do a much better job of blocking sound than plants alone.

• The berm should be at least eight feet tall and 20 feet wide, and as long as possible. A solid, well-planted berm can cut auto and truck noise by 70% to 80% and substantially reduce sounds from playgrounds, sporting activities, or factories. 

Barrier Walls

Since highway right-of-way widths are generally very narrow, there is usually limited space available to plant wide buffer areas of dense trees and shrubs along the highway to reduce the noise impact on adjacent property owners. Solid noise barrier walls are now being installed along many portions of highways where abutting residential communities have complaints with traffic noise.

The plants can provide aesthetic visual enhancements to psychologically reduce the scale of the wall by breaking up the expanse of the wall surface and the hard edges of the ends and caps. Planting on each side of a sound wall with taller growing trees that will over-top the height of the wall can visually reduce the apparent wall height. Shrubs planted in front of the wall and vines growing on the wall surface and over the wall top can effectively break up the surface expanse of the noise wall.

Good Sound Barrier Plants

• Bamboo is one of the best sound barrier plants to grow. In zone 8 or higher, plant one of the Bambusa multiplex varieties, which range from three feet in height to 25+ feet in height. In colder zones, Bambusa will sometimes lose some leaves during the winter. Bamboo, once topped, will remain at that height for the duration of its life and Bambusa are clumpers, meaning that it is not invasive and will not take over the landscape.  Although Bamboo is technically a grass, it can be considered a tree in this application.

• Other good sound barrier plants include: abelias, junipers, and antique, wild, and species roses.

• Barberry and even some particularly thorny cacti are commonly used as barriers.

• Dense hedges of pyracantha will keep out all but the most determined intruder. Long thorns make this plant hazardous to your health.

• Consider planting tall-growing shrubs with dense foliage such as Nandina, Callistemon, Buxus, Ligustrum, Photinia, or Escallonia. These hardy shrubs will muffle the offending noise while beautifying the landscape at the same time.

• Thickets of sassafras and pawpaw have been found to be relatively effective for this purpose.

• Also plant a mix of evergreens such as arborvitaes, spruces, pines, and hollies. To be effective sound barriers, these trees must have foliage that reaches to the ground.

Regardless of the plants selected, they must be thick, and not necessarily tall. As with any planting effort, the selected plants must be hardy to the area; able to adapt and grow in the environmental factors of the site such as soil type, moisture availability, wind conditions, winter road salt spray, drought tolerance, full sun exposure; and planted at a safe distance away from the roadway.

Sources

• Haworth, Kim, "In My Garden: Working Plants", Regional Reports, January 1, 2009

• Lerner, Joel M., "A Good Wall, Even if It's Made of Plants, Can Reduce Highway Noise", Washington Post, March 12, 2005

• Whaley, John T., "A Brief Look at Using Plants as a Sound Barrier", Urban Forestry News, Pennsylvania Community Forests Newsletter, Vol. 15, No. 3, Summer 2007

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

CaUFC credits for this article will be awarded 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.

Tree of the Seminar
Edited By Len Phillips

Princeton Elm is a large tree and is ideal for urban sites. It has a vase shape, is DED resistant and is an ideal tree for forming a canopy over the street. 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 and Jared Bookhardt from Sharp Top Trees.

Trade Name:                   Princeton Elm

Botanical Name:            Ulmus americana

Parentage:                      Selection from genus by Princeton Nurseries

Family:                             Ulmaceae

Year of Introduction:   1920

Height:                            60' - 80'

Spread:                           40' - 50'

Form:                              Upright vase shape

Bloom Period:              Early spring

Flower:                           Greenish red in March

Fruit:                               ½" long samara, greenish, mature in May - June

Summer Foliage:         Dark green leaves in summer, leathery

Autumn Foliage:          Yellow in autumn

Winter Color:                Dark grayish bark

Bark:                               Dark gray with ridges, often scaly

Hardiness Zone:          2b - 9

Growth Rate:                Fast, up to 3 feet per year, some nurseries have 
                                         reported 6 ft/yr

Site Requirements:     Tolerates urban conditions, prefers rich,
                                          moist soils, any pH, very drought and
                                          wet soil tolerant

Pest Resistance:         Resistant to Dutch Elm Disease and elm leaf beetle

Storm Resistance:      Excellent due primarily to deep roots

Salt Resistance:          Excellent

Planting:                       Easily transplanted, fibrous root system

Pruning:                       Prune in autumn

Propagating:               Rooted cuttings preferred (budding or grafts may be
                                        placed on DED susceptible root stock)

Design Uses:              Medium texture, good for homes, streets, parks, and 
                                        commercial landscapes. Deep roots will not cause
                                        sidewalks to buckle.

Companions:              Looks good with ornamental grasses due to its deep
                                        root system

Other Comments:      Excellent for street tree use, excellent branching, fall
                                        leaf color, growth rate, winter storm tolerance and form.

Available from:           Select nurseries, some are offering bare root whips
                                        by mail order to municipalities and homeowners

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.

CaUFC credits for this article will be awarded 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.

Recent Mulch Research
By Stenn Design

Urban Tree Utilization
By Dr. Steve Bratkovich, Dr. Jim Bowyer, Kathryn Fernholz, & Alison Lindburg

Introduction

Most analyses related to U.S. timber land and timber production, focus on forest land that is producing more than 20 cubic feet per acre per year of industrial wood crops under natural conditions. It's quite reasonable to focus research and attention on the commercial forest lands due to their size and economic, social, and environmental importance. However, urban forest areas are rarely researched or discussed regarding their potential to provide wood-based products.

It's estimated that today there are nearly 4 billion urban trees in the U.S., with another 70 billion trees growing in metropolitan areas. As urban land in the U.S. expands, so do the urban forests. Urban land in the lower 48 states increased from 2.5% of total land area in 1990 to 3.1% in 2000, an area about the size of Vermont and New Hampshire combined. Researchers from the U.S. Forest Service are projecting that urban land in the U.S. will nearly triple in size by 2050. This is an area larger than the state of Montana.

Utilization of urban trees for wood and paper products is still in its infancy. However, the idea is drawing more attention from researchers, community officials, arborists, tree care firms, and wood-using industries including bio-energy producers.

Available Wood in Urban Areas

Various researchers have addressed this question in different ways since the early 1990s. The following are different perspectives on the volume of urban trees removed on an annual basis from across the U.S.

• In 1994 the NEOS Corporation of Lakewood, Colorado, conducted the first national inventory of urban tree residues. A survey was conducted of generators of urban tree residues including commercial tree and landscape care firms, municipal/county park, recreation, and tree care departments, and electric utility power line maintenance firms. The results of the study indicated an annual urban tree residue volume including chips, logs, tops, brush, and stumps, of over 192 million cubic yards. This figure converts to about 25 million dry tons dry of residue. 70% of the wood residue was either given away, land filled, or left on site, with only 25% reported as recycled, sold, or used for a product.

• A 2003 report issued by the USDA Forest Service, estimated that in 2002, urban wood residues in the municipal solid waste stream totaled 14.8 million metric tons of chips, logs, stumps, tree tops and brush. About 8.5 million metric tons were recovered, mainly for compost and mulch. Of the remaining 6.3 million metric tons, 1.5 million were sent to combustion facilities, 1.6 million were deemed unusable, and 3.2 million metric tons were available for further processing. Interestingly, the total of 14.8 million metric tons was greater than the total estimated weight of timber harvested from U.S. National Forests during this same time period.

• A report from the U.S. Environmental Protection Agency in 2007 estimated that in 2006 "yard trimmings" in the municipal solid waste stream totaled 32 million tons. This estimate includes grass clippings, leaves and other non-woody residue. The urban tree and woody residue portion of the yard trimmings amount is estimated at nearly 19 million tons.

• A different approach to estimating the volume of urban trees removed on an annual basis is to look at urban tree inventories and apply an estimate of annual removal rates. This method eliminates the need to depend on survey respondents to quantify how much residue they divert from, or contribute to, the municipal solid waste stream.

• In 2002, using high resolution radiometer data to estimate urban tree cover, and combining this information with biomass equations adjusted for trees growing in an urban setting, an estimate of carbon storage in urban trees was obtained. Using this method, urban trees were estimated to contain over 704 million metric tons of carbon and an above-ground estimate of over 1.7 billion tons of 'standing biomass' in our urban communities. At a conservative one percent annual removal rate for urban trees due to storms, pest attacks, construction, life span, etc., the standing urban tree biomass removed on a yearly basis is estimated at approximately 17 million tons.

Consequently the volume of urban tree removals is a substantial number. The estimates range from over 16 to 38 million tons per year which is comparable to total annual harvests from America's National Forests. However, it is the metropolitan areas that will absorb the majority of the predicted urban growth during the next half-century.

Constraints to Utilizing Urban Wood

There is a long list of reasons that urban trees aren't always utilized to their best and highest value. Here is a quick look at some of the more common constraints.

• There is a perception that urban trees have 'zero' value.

• Urban trees typically have shorter trunks and more branches.

• They also have embedded materials such as nails, cables, and other hardware.

• Most individual urban tree removal projects generate small quantities of wood. Most wood industries can't afford to drive around town picking up one or two logs.

• Most timber sales in rural forests involve multiple tree species. This product variety interests a range of potential buyers and markets. Now after an invasive species attack (for example, emerald ash borer or Dutch elm disease), the availability of a single species or two is more the norm, limiting the number of potential buyers and markets.

• Tree inventories in urban areas often lack the scope and specificity (such as log volume and grade) needed by wood-using industries to set-up an effective utilization program.

• Most urban forestry programs have weak or non-existent wood utilization plans.

• Community leaders have little time to develop plans to dispose of urban trees. Most communities don't care what happens to the wood, as long as it is removed in a timely manner.

• When the expense of working in a city is considered in the light of a general lack of enthusiasm by many wood industry firms, the constraints of utilizing the urban wood seems daunting.

Urban Tree Utilization Industries

Most of the firms that utilize urban trees are small or are part of a larger business.

• Horigan Urban Forest Products in Skokie, Illinois, a suburb of Chicago, is one example of a company focused on lumber products. They stock hardwood lumber that caters to furniture makers, flooring and remodeling contractors, and individual homeowners and hobbyists.

• East and West Coast Urban Tree Utilization Businesses CitiLog, based in Pittstown, New Jersey, built its urban tree utilization business model on contracted services. For example, a recent project with the University of Pennsylvania took trees removed from campus that will be returned to the school as finished bookcases and tables.

• Pacific Coast Lumber in San Luis Obispo, California, mills and fabricates various products including small out-buildings, sheds, and cabins, as well as Adirondack furniture, benches, and picnic tables. Also, custom milling accounts for about 30% of their business. Renewable energy is the next product market they are looking at.

• Community recycling and reuse centers, LEED projects, and other green building efforts have provided new markets for lumber and related products from urban trees. As an example, the ReUse Center in Ann Arbor, Michigan, stocks locally produced lumber from urban sawmills. In the future, the green building sector will likely continue to grow as a market for urban wood products.

Bio-Energy

Another industry in a position to use large volumes of urban tree biomass can be found in the bio-energy sector. An example of the synergy between bio-energy and urban trees can be found in downtown St. Paul, Minnesota where a combined heat and power plant serves the commercial, industrial and residential downtown area. Completed in 2003, the plant was built as a multi-fuel unit, capable of burning coal, natural gas, or biomass in the form of wood chips. The long-term goal is to have 75% or more of the fuel for the plant to be biomass.

In addition, urban trees are not the only urban wood resource that can be tapped for energy. When combined with construction and demolition wood, discarded wood pallets and related shipping containers, and other forms of recyclable urban wood, the potential for urban areas to serve as local wood baskets or supplement existing wood baskets for industrial energy producing applications is compelling.

The Bottom Line

Urban areas, and adjacent "metropolitan land", will continue to grow throughout the U. S., consequently expanding the size of the urban forest. The estimated volume of urban trees removed annually varies but the total volume is significant. Urban forests contain a wood fiber resource that is in its infancy of being utilized for wood and paper products; however, the future looks promising. More attention including research, education, and technology transfer should be given to this resource in light of its ability to provide useful products including lumber and bio-energy, conserve landfill space, and generate economic opportunities.

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.

CaUFC credits for this article will be awarded 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.

Split Bark from Glyphosate Use 
By Candace Pollock

Glyphosate products, such as Roundup, may be a killer of weeds, but researchers are finding that the product may also damage landscape and nursery woody plants. Researchers at The Ohio State University (OSU) Extension said that glyphosate applied improperly is causing a phenomenon known as split bark. During the tree's uptake, the chemical is deteriorating the bark structure and destroying the winter hardiness of the tree.

The cosmetic damage makes the tree not saleable and is costing the landscape and nursery industries millions of dollars per year in damaged products. The economic cost to the U.S. nursery industry from split bark is conservatively estimated at $6.6 million a year. That's roughly 2.5% of finished inventory. Add to that the conservative estimate of $14 million in landscape tree failures, and people are starting to take split bark seriously.

How Damage Occurs

For a long time, the industry felt that split bark was an environmental problem, driven mainly by cold temperatures. But OSU has been receiving reports of split bark in warmer parts of the country, such as the Southeast and California. Winter temperatures are part of the problem, but only because glyphosate weakens the bark structure enough to cause the trunks to split under stress. The first step in controlling split bark is recognizing that glyphosate could be a contributing factor.

Glyphosate uptake leads to an accumulation of a type of acid called shikimic acid that results in a reduction of phenolics which are plant compounds that serve a variety of roles in plant development and survival, including defense against pathogens. Research has found that the more glyphosate is taken up by the plant, the higher the shikimic acid levels. In addition, glyphosate stays within the plant for years, being stored in the roots with sugars in the summer and fall, and then translocating to areas of the plant where growth takes place in the spring and continuing to cause injury.

Which Glyphosate to Apply

In situations where glyphosate is required, users should pay attention to which product they apply. The formulations for glyphosate have changed over the years and it is now more potent than the older products were. Plus, more generic brands are now available, and they are cheaper to come by, so users are getting more lax in their applications.

The most recent research has shown that it's not the glyphosate itself that is causing split bark, but the surfactant found in some glyphosate products. A surfactant is a wetting agent that allows for easier spreading of the chemical, and increases uptake of the chemical in woody plants. Surfactants are known as adjuvant loads on glyphosate product labels.

When glyphosate use is necessary around trees, use a glyphosate product that has no adjuvant load. Fourteen registered glyphosate products contain no adjuvant load. They include: Backdraft, Campaign, Expert, Extreme, Fallowmaster, Fallow Star, FieldMaster, Glypro, Landmaster BW, Land Star, ReadyMaster ATZ, Rodeo, Roundup-Custom, and RU SoluGran. *

Apply Glyphosate Properly

Nursery and landscape professionals should use glyphosate only when necessary. For example pre-emergent glyphosate applications to kill weed seedlings are better than a post-emergent application that kills the entire weed plant. This reduces the impact on woody plants, as well as saves money. Adoption of integrated weed management programs with reduced reliance on glyphosate can cut herbicide expenses and application labor up to 50%.

Nursery and landscape practitioners are also encouraged to apply glyphosate products properly. A Horticultural Research Institute funded project conducted last year found that many growers and nursery/landscape professionals were using glyphosate indiscriminately by:

• making applications (one quart per acre) as frequently as eight times a season, or approximately every 2.5 weeks

• removing suckers with glyphosate products

• applying the product so close to woody plants as to increase uptake through drift exposure

Glyphosate should not be used to remove suckers. There should be a 30-foot buffer between the weeds being spraying and the woody plants and glyphosate should not be applied frequently. Research has shown that one single dose of glyphosate with surfactants stays in the plant for at least a year.

Glyphosate injury is also difficult to diagnose because symptoms may not be present for up to two years after glyphosate absorption. In addition to split bark, other symptoms include witches broom, stunting, loss of apical dominance, individual dead limbs, chlorosis, and pre-mature death.

Susceptible Trees

Woody plants most susceptible to glyphosate uptake include:

• Pyrus species, especially Callery pears

• Prunus species, especially Yoshino cherry and Kwanzan cherry

• crabapples

• sycamore

• serviceberry

• hawthorn

• mountain ash

• black gum

• paperbark maple

• Japanese maples, especially variety dissectum

• Norway maple, especially 'Emerald Queen'

• red maples

• dogwood, especially Kousa

• magnolias, especially 'Elizabeth'

• yellow magnolias such as 'Butterflies', 'Sawada's Cream', 'Yellow Bird', and 'Yellow Lantern'

Conclusion

Researchers are working to develop a glyphosate product that is safer to use for weed control around landscape and nursery woody plants. Until safer glyphosate products are developed, a change in weed management practices in the nursery and landscape industries is required to control the split bark phenomenon.

Source
"Improper Glyphosate Use May Be Causing a Phenomenon Know as Split Bark", News Release No. 132, Ohio State University Extension, January, 2009

*Note: The mention of specific products does not indicate an endorsement of these products, but are listed for your information only.

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.

CaUFC credits for this article will be awarded 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. 

Diversification Planting

Edited by Len Phillips

There's very little diversity in the urban forest. Here is what the problem is and what you can do about it.

The Problem
Most insect and disease problems are host specific. For example, in the 20th century chestnut blight wiped out almost every American chestnut in the United States and then Dutch elm disease decimated American elms throughout the country. When the chestnuts and elms were gone, the durable, fast-growing and relatively disease and pest resistant ash, became the shade tree of choice for municipal foresters, developers, and homeowners. It was thought that there were only a handful of trees that tolerate the stresses of urban life: pollution, drought, and salt. Besides the ash, they include the over-planted honeylocust, silver maple, and Norway maple. Now these trees are having pest problems and may soon join the chestnut and elm as problem trees.

The Solution
Planting a diversity of tree species helps ensure that only a portion of the landscape will be at risk if a host-specific insect or disease problem becomes an epidemic. Using a diversity of species can reduce both the spread of tree disease and the effect of a disease on the overall tree cover. Dutch Elm disease, gypsy moth, oak wilt are all reasons to plant a diversity of species - starting now. Diversity is also aesthetically pleasing and good for wildlife habitat.

• Frank Santamour of the US National Arboretum proposed the following diversification plan. No planting plan should contain more than 10 percent of one species, 20 percent of one genus, or 30 percent of one family. Therefore, for every 100 trees planted, care should be taken than no more than 10 trees of any one species such as Red Oak and no more than 20 trees of any one family such as oaks are planted.

• Some communities (such as Portland, Oregon) also specify a deciduous (60%) to evergreen (40%) ratio.

• Other cities (such as Lansing, Michigan) have a diversification policy that states: "No tree will be planted next to a tree of the same species and at least four genera will be planted on a street."

• Another means of diversification is by size distribution of the tree population. That follows a 40-30-20-10 rule (40% of young trees 0"-8" dbh; 30%, 9"-16"established trees; 20%, 17"-24" mature trees; and 10%, >24" very old trees).

What does diversity really mean?
The diversification formula should be carried one step further than a planting plan. It should be applied to the existing street tree inventory so that dependence on a single species from previous or natural plantings will not be carried forward into future plantings. The diversification formula was set up so that if 10% of a city's tree population was Red Oak and a disease or insect killed them all, then 90% of the urban forest would still remain. The American Elm comprised as much as 50% - 90% of the urban tree population before Dutch Elm disease devastated the elm landscapes across North America.

One note of caution, the diversification formula may be very difficult to use in zones 2 and 3 as well as in other locations where the number of trees is severely restricted due to soil or climatic conditions.

How do communities invoke a program that enhances diversity?
Start by inventorying the urban forest (random sample or 100% inventory) to determine what the population looks like. Upon reviewing the data and policies of these programs, four clear patterns of species distribution are evident. They are:

1.  Typically, only a handful of species dominate the population. For example, it is not uncommon for a community to have 25% to 70% of the street tree population comprised of only one species.
2.  Dominant species are often a result of past planting programs and these now tend to be considered high maintenance species by the community.
3.  Many communities currently focus on providing short lists of acceptable species for planting in streetscapes. In many cases, these very brief lists have not changed in over a decade, and they perpetuate near monoculture populations.
4.  Dispite this, with few exceptions, a relatively large variety of species can be found in a community. Even for a small community it is possible to identify over eighty species and cultivars.

The negative aspects of the patterns identified above are significant. Managers invariably deal with a large number of trees planted decades ago that would now be considered inappropriate because of their high maintenance costs. A large portion of current municipal forestry budgets are devoted to maintaining these trees. Current planting programs that offer a very narrow range for species selection have a tendency to promulgate near monoculture plantings and, over time, actually reduce the number of species in the population.

By analyzing the inventory and historical data, it is evident that the potential planting palate for a community can be very large. There are many appropriate species that are underutilized. A strong emphasis should be placed on understanding the species composition of a community and the trees should be mapped at a higher order to understand species distribution.

Planning for Species Diversity
Enacting a species diversity program implies three actions:

1. Minimize overused species

2. Increase the planting of underused species

3. Introduce new species into the landscape

To achieve each of these elements, eight clear tasks have been developed. The first two tasks focus on evaluating the current and potential tree resource. The remaining six tasks outline a systematic process for establishing thresholds for each species and circulating species in and out of the annual planting list.

Task 1 - Compile and assess data on the current tree population and program
An inventory is the easiest tool for collecting and summarizing this data. Necessary information includes:

• Species count and percent representation in the population

• Number of vacant planting sites in the community

• Number of trees planted each year

• Number of trees removed each year

• Contents of the annual planting list

Task 2 - Develop a complete palate of all potential species to plant
Create a list of all trees that can potentially be planted in the area. The list should include everything from small to large; and abundant to obscure. This list can be derived from a number of sources:

• Current tree population

• Identify all species that currently appear to be doing well

• Planting lists from neighboring communities

• Local arboreta or botanic garden lists

• Tree, shrub, and landscape books

• Nursery catalogs that match zone restrictions for your area

Task 3 - Establish a target for each species on your current list
To minimize an over emphasis of any one species on the list, a cap for each species should be established. This cap should be a percentage of the total possible number of trees that can be present in the community (existing number of trees plus the number of vacant planting sites).

Task 4 - Develop a short list of species to plant each year
Develop a short list of anywhere from five to twenty species. This is the list of species that are going to be emphasized in the current year's planting program. The list should incorporate a variety of species in each of the various size categories determined in the community. The number of species in each size category should be proportional to the number of planting sites in each size category. 

Task 5 - Create a threshold for each species on your annual planting list
To minimize an over emphasis of any one species on the annual list, a cap for each species should be established. For example, if 100 trees are being planted this year, a maximum number of any one species from your list should be established. As that threshold is reached, that particular species is taken off of the list for the remainder of the year. This does not mean that the first development that gets planted can use up that entire species for the year. A careful balance of all of suggested species for the year will guarantee an even and equitable distribution of the 100 trees.

Task 6 - Establish a planting cycle for each species
Each species stays on the annual list for a few years. The duration is anywhere from three to five years and is a function of how much emphasis will be placed on that particular species (the current versus the target).

Task 7 - Rotate species in and out of annual list
Once a species has reached the end of its planting cycle, it is taken off the list for a few years. Other species are then placed on the annual list to encourage their emphasis. This down time is temporary and should last anywhere from three to five years for any one species.

Task 8 - Evaluate the program
No program is complete without the ability to gauge whether or not the program is successful. The best way to assess the success or failure of a diversification program is to compare the change over time to the individual species count and compare that count against the targets you have established for each species. Continue to assess the suitability of species, incorporate changes due to insect pests, diseases, and cultural or other realizations.

Sources

• Arbor Day Foundation, "Tree Basics", Arbor Day, May/June 2008

• Duntemann, Mark, "Urban Forestry Management Series: Implementing a Species Diversity Program", Natural Path Urban Forestry Consultants, July, 2004

• Peltier, Patrice, "A Forest of Diversity - Variety Softens Blow When Tree Disease Hits", Milwaukee Journal Sentinel, Aug. 20, 2006

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

CaUFC credits for this article will be awarded 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.

Urban Forestry Standards

Edited by Len Phillips

This article is about production standards and was compiled by members of the Society of Municipal Arborists (SMA). The information has been gathered from a variety of sources, listed at the end of the article. It is presented here as a guide for anyone who has been assigned the task of zero based budgeting.

Task                                                    Labor Hours per Tree
Planting Trees
Plant tree 5' - 6' high                                  0.45
Plant tree 2" - 2-1/2" dia.                           1.0
Planting 2" tree by bare root planting         0.5
Planting tree by tree spade                       4.0
Watering a newly planted tree                   0.3

Trimming Trees
6" diameter - by hand                                0.5
6" diameter - by lift truck                           0.4
9" diameter - by hand                               0.8
9" diameter - by lift truck                           0.6
12" diameter - by hand                             1.1
12" diameter - by lift truck                         0.8
18" diameter - by hand                             1.6
18" diameter - by lift truck                         1.1
24" diameter - by hand                              2.2
24" diameter - by lift truck                         1.6
30" diameter - by hand                              2.7
30" diameter - by lift truck                         2.1
36" diameter - by hand                             3.2
36" diameter - by lift truck                         2.4
48" diameter - by hand                             4.0
48" diameter - by lift truck                        3.4

Tree Removal
Up to 6"                                                    1.0
6 - 12"                                                       2.0
12 - 18"                                                     4.0
18 - 24"                                                     6.0
24"+                                                         10.0

Stump Removal
Up to 6"                                                     1.0
7 - 12"                                                        2.0
13 - 18"                                                      4.0
19 - 24"                                                      6.0
25"+                                                         10.0

Tree Fertilization
Punch in soil (10 yr. old tree)                     0.5

Pest Control in Trees
Power spray foliage                                  0.3
Systemic spray in soil                              0.15

Planting Shrubs
Plant shrubs individually                          0.6
Plant shrubs in a group                           0.3

Shrub Maintenance
Prune a mature deciduous shrub              0.5
Prune a mature evergreen shrub              1.0
Properly pruning a mature yew shrub       4.0
Weed, till, and edge a shrub bed              1.0 per 1,000 sq. ft.
Rake a shrub bed                                     0.85 per 1,000 sq. ft.
Mulch a shrub bed                                     0.5 per 1,000 sq. ft.

Item                                                          Standard
Total Forestry Budget                             $ 5 per capita 
                                                                 $10 per tree

Forestry Budget                                     Breakdown
Tree planting                                             more than 5%
Removals                                                  no more than 30%
Scheduled pruning                                   more than 50%
Emergency pruning                                  no more than 25%
Demand pruning                                       no more than 25%
Supervision                                               no more than 30%

Policies
Tree removals = tree planting number      Yes
Pruning cycle                                               less than 8 years
Tree planting plan & regulations                Yes
Management plan                                       Yes
Street tree inventory                                    Yes
Pruning guidelines                                      Yes
Removal regulations                                   Yes
Advisory Board                                           Yes
Conducting/contributing to research         Yes
Training & education program for staff     30 hours/year
Training & education program for workers    20 hours/year
Certified Arborists                                       1 employee/crew
CPR training                                                1 employee in 10
Trained in aerial rescue                              1 employee/crew
Certified pesticide operator                       1 employee/crew

These numbers will all vary depending upon various factors: size of trees; weather; travel time to and from job sites and forestry shop; entitled rest periods from work, etc. Based on these factors, 6.5 hours/day or 80% of the work day is the standard for time spent in performing assigned tree maintenance work.

Sources:

• McGannon, Jim, "Urban Forestry Programs Across America", City Trees, July/Aug 2001, pg. 17
  
• Municipal Forestry Department Accreditation Program, Society of Municipal Arborists, 1999, pg. 5

• Phillips, Leonard, Urban Trees, McGraw-Hill, 1993, pg. 90

• Schwab, Steve, "Tree Trimming Productivity Standards", City of Lincoln Parks & Recreation Department - Forestry Section, 2004.

• Tree Maintenance Standards, American Parks & Rec. Society, reprinted in City Trees, May/June 2001, vol.37, No.3, pg. 36

• This list was originally published in City Trees, Sept./Oct 2001, pg. 4

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.

CaUFC credits for this article will be awarded 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.

Research Briefs 

Edited by Len Phillips
 

Landscape Performance of Birch

Mengmeng Gu, James A. Robbins, and Curt R. Rom

Twenty birch genotypes were planted in April 2002 to evaluate their survival, growth, and response to two irrigation treatments. The results are:

• Betula pendula 'Trost's Dwarf', B. ermanii, and B. albosinensis had the lowest survival rate.

• Betula populifolia, B. nigra 'BNMTF', B. nigra 'Cully', and B. × 'Royal Frost' had the highest survival.

• Betula nigra 'BNMTF' and B. nigra 'Cully' were taller and had greater trunk diameter.

• B. utilis var. jacquemontii, B. papyrifera 'Uenci', B. populifolia 'Whitespire', B. maximowicziana, and B. lenta were the shortest and had the smallest trunk diameter.

• B. papyrifera, B. nigra and B. davurica had the greatest annual change in tree height.

Water-stress treatment reduced final tree height and trunk diameter in all birch trees.

Arboriculture & Urban Forestry Volume 33, Number 4 June 2007

Economic Patterns in U.S. Arboriculture

Christopher M. O'Bryan, Thomas J. Straka, Scott R. Templeton, and Judith D. Caldwell

Arboriculture is a distinct industry that provides unique services to provide for the health and care of trees. It is a developing industry and this development leads to questions on how the industry is organized and operates. The four largest arboricultural firms account for only 4% of combined industry receipts and the industry comprises nearly 82,000 establishments, employs approximately 160,000 workers, and earns annual gross receipts of nearly $9 billion.

Arboriculture & Urban Forestry Volume 33, Number 4 June 2007

Phosphite Injections Control Sudden Oak Death

M. Garbelotto, D.J. Schmidt, and T.Y. Harnik

Coast live oak trees were artificially inoculated with Phytophthora ramorum, the agent of a tree disease commonly referred to as sudden oak death. Phosphites were applied to trees. Injections of phosphites and bark applications of phosphites + the organosilicate surfactant Pentrabark^TM (Agrichem, Medina, OH, U.S.) were consistently effective in suppressing bark colonization by this pathogen without causing phytotoxicity.

Arboriculture & Urban Forestry Volume 33, Number 5 September 2007

Success of Verbenone Against the Mountain Pine Beetle

John H. Borden, Glen R. Sparrow, and Nicole L. Gervan

Pouches releasing verbenone, the anti-aggregation pheromone of the mountain pine beetle, were stapled to lodgepole pines. Post-flight assessment where almost all infested trees had been removed before beetle flight, revealed new mass attacks on 3.6% of available trees. Where no infested trees were removed, 19.6% of available trees were mass-attacked. The treatment with verbenone pouches at roughly 15 m (16.5 yd) centers is a useful tool for protecting trees from attack by the mountain pine beetle provided that verbenone is used as part of a multi-year integrated pest management program that also includes disposal of all infested trees in the area to be protected before beetle flight in midsummer.

Arboriculture & Urban Forestry Volume 33, Number 5 September 2007

Growth of Street Trees

Oliver Bühler, Palle Kristoffersen, and Søren Ugilt Larsen

Limited rooting space is considered a major problem for growth of street trees. Different approaches to extend the soil volume accessible to roots have been investigated. A survey investigated growth and vitality of trees planted in: 1) structural, load-bearing soil; 2) sand-based load-bearing soil; 3) so-called super planting pits and 4) trees planted in conventional planting pits. The results provide evidence that tree growth in both of the load-bearing materials allowing for root growth was found to be comparable to tree growth in conventional planting pits, and those methods are therefore considered applicable at sites where conventional pits cannot be established. However, tree growth in super planting pits was superior to the other methods in regard to growth rates and vitality.

A super planting pit offers a large, unsealed surface of >129.6 ft² (12 m²) in combination with deep soil loosening, providing at least 525 ft³ (15 m³) of soil for each tree. A typical super planting pit profile can be described as exchanged topsoil from 0 to 24 in (0 to 60 cm), exchanged mineral base soil from 24 to 32 in (60 to 80 cm), and loosened original soil from 32 to 48 in (80 to 120 cm) deep. The super planting pits provide extra rooting space in depth combined with a large open surface area results in high growth rates and high uniformity of the plantation.

Arboriculture & Urban Forestry Volume 33, Number 5 September 2007

EAB Density and Canopy Dieback in Ash

Andrea C. Anulewicz, Deborah G. McCullough, and David L. Cappaert

Emerald ash borer (Agrilus planipennis) (EAB), a phloem-feeding insect native to Asia, was identified in 2002 as the cause of widespread ash (Fraxinus) mortality in southeast Michigan, U.S. and Windsor, Ontario, Canada. Little information about EAB is available from its native range and it was not known whether this invasive pest would exhibit a preference for a particular North American ash species. We monitored EAB condition on green ash (F. pennsylvanica) and white ash (F. americana) street trees and white and blue ash (F. quadrangulata) trees in two woodlots. Green ash street trees had significantly more canopy dieback and higher EAB densities than white ash trees. In each of the woodlots, EAB densities were significantly higher on white ash trees than blue ash trees.

Arboriculture & Urban Forestry Volume 33, Number 5 September 2007

Response to Reduction Pruning Cuts

Jason C. Grabosky and Edward F. Gilman

Reduction pruning cuts were used to prune Quercus virginiana (live oak) and Quercus shumardii (shumard oak). One-half of the pruning wounds were harvested and dissected 3 years later to observe extent of discoloration in response to the pruning cut. Shumard oak did not limit discoloration as effectively as live oak. Discolored area in the wood increased with size of the pruning cut surface. The angle of the reduction cut relative to the American National Standards Institute-recommended angle bisect method was not found to influence discoloration. Discoloration in the less efficient compartmentalizing species (Shumard oak) was related to cut surface area, but not to cut angle. There was no relationship between aspect ratio and discoloration in the 3 years after pruning. The data suggest that reduction cuts can be made back to lateral branches as small as one-third the diameter of the removed stem.

Arboriculture & Urban Forestry Volume 33, Number 5 September 2007

Preventing Sapsucker Damage on Sugar Maple

E. Thomas Smiley, Donald C. Booth, and Liza W. Wilkinson

The yellow-bellied sapsucker (Sphyrapicus varius) is the primary cause of sapsucker damage on trees in the eastern United States. This migratory bird winters in the south and summers in northern states. Insects are a major part of this species diet; however, it is best known for making small wounds in stems and large branches and feeding on either phloem or xylem sap that oozes from the wounds. Phloem sap is the main source during the summer breeding season, whereas xylem sap is more readily available from deciduous trees after leaf drop in the winter. Sapsuckers will test many trees and select only those that have the highest quality sap to feed on repeatedly. Sugar and amino acid levels are often highest on trees that have injuries that restrict sap movement. Similarly, sapsuckers are thought to choose trees in poor health.

Symptoms of repeated feeding are horizontal rows of 0.04 in (1 cm) diameter holes in the bark. These wounds ooze sap that the bird feeds on. Excess sap may run down the surface of the bark and promote the growth of dark-colored fungi, a condition called "Black bark". Insects and animals, including squirrels, porcupines, hummingbirds, ants, hornets, and wasps, are also attracted to this sap food source. Some of these may cause more damage to the tree.

Although most trees do not exhibit severe decline from sapsucker attack, some studies have found a loss of growth and crown dieback associated with severe girdling. Sapsuckers have also been found to cause damage, which results in ring shake and the entrance of wood decay.

Wrapping trunks and branches with burlap is the traditional method to deter sapsucker wounds. However, no published studies could be found that quantify the effectiveness of this treatment. This study was undertaken to determine the effectiveness of two different trunk wrap materials, burlap and polypropylene tree wrap, for preventing sapsucker feeding.

Arboriculture & Urban Forestry Volume 33, Number 5 September 2007

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Fertilization of Landscape Trees

Edited by Len Phillips

Research on trees transplanted from nurseries indicates that there is little benefit to fertilizing at planting. Tree fertilization is not recommended on native soils because it is usually not needed. Conifers rarely need fertilization at all since most are adapted to low-nutrient soils.

With this being said, many arborists feel they must respond to customers who demand fertilization of their trees. Municipal arborists may see trees in stressed conditions where fertilizer might help. Therefore this article discusses the best fertilization practices at the present time, if fertilization is deemed necessary.

Determining the Need for Fertilizer

The best indicator of whether fertilization is necessary is a soil test. Ideally, a soil sample should be taken before trees are planted. In the absence of a soil test, the next best indicator of the need for additional fertilizer is shoot growth over the past three years. If current shoot growth is in excess of 6 inches, then fertilization is unnecessary. If shoot growth is between 2" and 6" (5 - 15 cm) then fertilizer may be applied and if shoot growth is less than 2 inches (5 cm), then fertilizer applications are appropriate. Foliage color is another indicator of the need for fertilizer. Yellow leaves may indicate the need for fertilizer as this symptom generally occurs on trees that are not taking up enough nutrients. A final indicator is the history of the location. Trees in locations that are fertilized for turf on a regular basis rarely need to have supplemental fertilizer applied. In such locations, supplemental fertilizer should only be considered if shoot growth is less than 2 inches (5 cm), or if a soil test reveals a specific nutrient deficiency.

Low soil pH levels (5.5 and below) may negatively affect trees by reducing the availability of useful nutrients and increasing the availability of aluminum, a potentially toxic element. In low pH soils, lime can be applied to raise the pH, and this is best done before a tree is planted.

Application Techniques

Many trees are injured each year by improper fertilization. Mistakes due to calculation errors during mixing, poor technique, or incorporating the wrong chemical into the tank mix are all too common. While improper mixing and application account for some tree deaths, researchers have also discovered that excess nitrogen and phosphorous (even at the recommended rates of 4 to 6 lbs N/1,000 sq. ft.) have been shown to cause the loss of beneficial mycorrhizal activity and to increase pathogenic activity in the soil.

When to Fertilize

Most trees experience a single flush of growth during spring followed by slower growth throughout the summer and fall. Because it is desirable to have nutrients available to the tree before the spring flush begins, the most beneficial time to apply fertilize is late fall or winter. However, winter applications can extend from when the ground is workable in the spring until just before trees start growing a month later. Fertilizer should not be added during the spring growth period.

If a tree shows a sign that might indicate a nutrient deficiency, fertilizer can be applied at any time during the growing season. If fertilizer is applied under hot and dry conditions, it is important to provide water for the tree soon after the fertilizer is applied so that salts from the fertilizer do not build up and damage the tree's root system. One inch of water should be applied every week around the area where fertilizer was applied.

What to Apply

A soil test provides the best indicator of elements that may need to be added to the soil to prevent nutrient deficiency problems. Unless a tree is deficient in some other element, increased nitrogen (N), more than other plant nutrients, has the most pronounced effect on the growth. However, if an increase in N produces a visible increase in growth, other elements may still be required.

High rates of phosphorous (P) should not be applied unless a need is indicated by a soil test. High rates of P can negatively affect the environment, especially lakes and streams. Never use a fertilizer that includes any kind of herbicide around a tree. These fertilizers may be beneficial to turf but can damage broadleaf trees.

Application Rates

Trees typically go through three stages of nitrogen needs.

1. During the newly planted phase, quick release N levels should not exceed 0.1 lb N/100 sq. ft. (45 g. N/10 sq. m.) per year, or a higher rate of a slow release fertilizer, up to 0.2 lb N/100 sq. ft. (90 g. N/10 sq. m.) per year can be used. Slow release and natural organic fertilizers can be incorporated into the backfill soil. Quick release fertilizers should be broadcast after planting and then watered in. Do not mix quick release forms with the soil used to backfill the planting hole, because direct contact with fertilizer will burn the roots.

2. On young landscape trees and shrubs where rapid growth is desirable, use 0.2 to 0.4 lb N/100 sq. ft. (90-180 g. N/10 sq. m.) per year. For trees in lawn areas, do not exceed 0.1 lb N/100 sq. ft. (45 g. N/10 sq. m.) per application unless a slow release or natural fertilizer is used. Higher rates will burn the grass. Recent research indicates that fertilizer at this stage results in only a slight enhancement of tree growth.

3. As trees and shrubs mature and the growth rate slows down, the need for N drops to the level needed to maintain landscape plants in a healthy condition without excessive vegetative growth.

Too much nitrogen fertilizer will push leaf development at a rate faster than the roots can support. Too much fertilizer will also cause fertilizer burn. This occurs because the high concentration of fertilizer draws water out of the root and into the soil, in turn causing a 'drought condition' to occur in the tree. Flooding the root zone with water should reverse the problem, provided the soil is well drained.

Surface Fertilizer Application

Plants respond best to surface applications of fertilizer broadcast over the area where the tree roots lie. A late fall or winter application will let the tree get the maximum value from the nutrients. Dry or granular fertilizers can be applied by hand or with the use of a mechanical spreader. Trees should always be watered around the area of fertilizer application soon after the fertilizer has been applied. This helps to ensure that the fertilizer will move down to the tree's root system before it can be taken up by weeds or grass. A good rain (1 - 2" or 2½ - 5 cm) will also be sufficient to move fertilizer to the tree's root zone. However, environmentalists stress not fertilizing prior to a rain due to risk of groundwater contamination should too much fertilizer be applied or too much rain occur.

Drill-hole Fertilizer Application

For established trees requiring phosphorus or potassium, or to apply a higher rate of fertilizer than 0.1 lb N/100 sq. ft. (45 g. N/10 sq. m.), fertilizer can be applied using the drill-hole method. This method is advantageous for supplying phosphorus and potassium to trees because these nutrients are relatively immobile in soils. Drilling holes will reduce soil compaction and increase aeration. The drill hole method is, however, extremely time consuming and is generally only used by professional arborists and landscapers for high value trees and trees under extreme nutrient stress.

The drill-hole application method involves digging holes in a grid pattern 2 feet (0.6 m.) apart using a soil auger, with the tree at the center of this pattern. Holes should be 1½ to 2 inches (30-50 cm.) in diameter and 1-1½ feet deep. The holes should be drilled in a series of parallel lines beginning 3 feet (1 m.) from the trunk and extending 2 feet (0.6 m.) beyond the drip line. For columnar trees, holes should be drilled 4 to 6 feet (1.2-1.8 m.) beyond the drip line. To calculate the amount of fertilizer to place into each hole, use the following formula: (100/analysis of N in fertilizer) × 0.12 = amount of fertilizer to add to each hole in teaspoons. For example, if you are using a fertilizer with an analysis of 18-8-8, then use (100 /18) × 0.12 = 0.66 or 2/3 teaspoons of fertilizer per hole. After the holes are drilled, place the recommended quantity of fertilizer in each hole, water the fertilizer in, and refill the holes.

Hydraulic Fertilizer Application

Hydraulic injection of liquid fertilizers into the root zone of the tree is an acceptable way to provide nutrients and may be offered by some specialty tree care companies. The use of specialized equipment and fertilizers for this method can be costly. However, when a large number of trees need to be fertilized, this system may be economical. Injections are applied in a grid pattern similar to the drill-hole method except that injection sites should be 3 feet from each other and should extend 15 feet (4.6 m.) from the base of the tree. Hydraulic injection allows nutrients, including immobile elements, to be available to the tree more rapidly than any other method of fertilizer applications.

Foliar Fertilizer Application

To rapidly correct particular micronutrient problems (iron, zinc, and manganese), a foliar fertilization supplies nutrients directly to the leaves, where they are needed. Foliar applications, usually made to landscape trees with a hand held sprayer, are effective in correcting specific nutrient deficiencies for a short period of time. Soil pH adjustment and additional soil application of these nutrients are required to correct the problem long term. Pesticides can also be applied as a foliar spray. However, foliar sprays are difficult to apply to large trees and the materials will sometimes leave a whitish film or spots on the leaves.

Fertilizer Injection Application

Another rapid way to correct micronutrient problems is by injecting these nutrients directly into the trunk of the tree. The micro-injection technique requires a good understanding of how a tree system absorbs nutrients, compartmentalizes wounds, and recovers from the small injury created during the process. To follow the basic guidelines of micro-injection, the arborist/technician must know proper placement, size, and depth of the injection hole, and the acceptable conditions under which proper injections should take place. When fertilizer is injected into the sap stream of the tree, the material moves quickly throughout the entire vascular system. The individual components go directly to where they are needed for optimum benefit to the tree.

pH Adjustments

In cases where the soil pH is above the optimum range for the growth of a particular plant species, interveinal chlorosis, or yellowing between veins, may occur on the foliage. This chlorosis is usually an indication of poor iron availability in the soil. Even though the soil may contain enough iron, the plant is not able to take up and use the iron efficiently. The solution is to decrease the pH of the soil and apply iron chelate to the leaves or the soil. Foliar applications of iron chelate need to be made several times during the growing season. A chart which is linked below, illustrates the optimum pH range for nutrient availability. http://web.missouri.edu/~umcsnrsoilwww/313/mn.htm17.jpg

Summary

It is not common that trees suffer from soil nutrient deficiencies; trees usually obtain enough nutrients from the soil in which they are growing. More often, the cause of the suffering is from inadequate water, poor or damaged root systems, or a high soil pH. However, if a newly planted tree is in poor soil or if there is a need for more rapid growth, fertilization can be beneficial. Water is still the overriding factor that usually determines plant health, even for established, mature trees.

Sources:

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

• Coder, Dr. Kim D., "Tree Root Growth Requirements", The Journal of The Society of Municipal Arborists Vol 38, Number 2 March/April 2002.

• Elliott, Marianne and Robert L. Edmonds, "Soil Nitrogen and Disease Severity in Pacific Madrone Habitats", Center for Urban Horticulture, University of Washington, Autumn 2001.

• Gillman, Jeff and Carl Rosen, "Tree Fertilization", FO-07410, University of Minnesota, Department of Horticulture, 2000.

• Gilman, Edward E. et. al., "Fertilizer Impact In Sandy Soil", Journal of Arboriculture 26(3): 177-182

• "Nitrogen Relationships of Ornamental Trees in Urban Settings: A First Look", 1998 Research & Technology Development Project.

• Shinano T., M Osaki, and M. Kato, "Differences In Nitrogen Of Trees", Tree Physiology 2001. 21:712-624

• Trowbridge, Peter J. and Nina L. Bassuk, "Trees in the Urban Landscape", John Wiley & Sons, Inc. 2004.

• Watson, G. and Dan Neely, "The Landscape Below Ground", International Society of Arboriculture, 1993.

Selected plants with the ability to withstand a pH of 7 to 8
Scientific Name	Common Name
Acer saccharinum	Silver Maple
Alnus glutinosa	Common Alder
Betula papyrifera	Paper Birch
Carpinus caroliniana	American Hornbeam
Catalpa speciosa	Northern Catalpa
Celtis occidentalis	Hackberry
Cornus sericea	Red Osier Dogwood
Juglans nigra	Black Walnut
Pinus banksiana	Jack Pine
Pinus nigra	Austrian Pine
Quercus bicolor	Swamp White Oak
Quercus macrocarpa	Bur Oak
Salix alba	White Willow
Tilia americana	American Linden
Tilia cordata	Little Leaf Linden

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