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Paper Birch & Douglasfir: An Odd Relationship

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Blog on Arbor Day Foundation website – written by James R. Fazio – February 15, 2018

Trees in a forest are usually thought of as fierce competitors, each struggling for control of available light and soil moisture, usually at the expense of neighboring trees. But Canadian researcher Suzanne W. Simard and her colleagues found that Paper Birch trees can actually aid their neighboring Douglasfirs.

Through carefully controlled research, Dr. Simard has documented the transfer of carbon (sugar) from the Paper Birch to nearby Douglasfirs. The transfer takes place through tiny underground strands of beneficial fungi called ectomycorrhizae. These appendages are common on most tree roots. They illustrate a classic symbiotic relationship in that both the host and the fungus benefit from the close association. The fungus obtains a small amount of carbohydrates and vitamins from the tree and in turn greatly increases the absorptive surface of the root. This increases the flow of water and essential elements into the tree roots, especially phosphorous.

Dr. Simard discovered that the mycorrhizae on Birch and Douglasfirs in her research plots interconnected. Sugars flowed between the tree roots, with a net gain for the Douglasfirs. She also found that the more the Douglasfirs were stressed by shade, the more of a sugar fix they received from the Paper Birches.

 

There may be management applications of this phenomenon. By interplanting the two species, or encouraging natural regeneration of both, the birches may help the longer-lived conifers get a growth boost early in life and at the same time help crowd out competing vegetation in a plantation. Eventually the birch could be harvested when overtopped by the Douglasfirs. As an added bonus, scientists have noticed that birches also have an “antibiotic” effect on soil pathogens that cause root rot.

Sycamore Trees And Frost Crack From Winter Temps

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Blog edited from Tree Services Magazine article by VIC FOERSTER — FEBRUARY 7, 2018

A couple of weeks ago, local temperatures were quite frigid. During a similar stretch of severe weather up in west Michigan, most of their sycamore trees across town literally exploded. As a species, sycamores retain a great deal of water. The water within the wood can freeze to the point where the expansion in the wood cells causes tree trunks to burst.

Fissures, splits and cracks ran up and down hundreds of city trees. Many of them split open so far you could see completely through 30-inch diameter trees.

Several residents were wondering if their tree would survive or if they were in danger of falling. Having never seen anything like it before, a local arborist at first was unsure how to assess, but they proceeded to examine each and determined that some of the trees should be removed. Others were recommended to have trunks bolted, which, in essence, meant screwing them back together again.

Most of the trees, however needed no help, and when the temperatures warmed to a balmy positive 15 degrees, the fissures unexpectedly snapped shut. The trunks slammed back together so violently it sounded like gunfire. The police actually received so many calls about the so-called gun battles that a public notice was needed to reassure citizens.

Now years later, one can still see the vertical seams in the bark of those sycamores. During colder winters, the seams separate slightly, just not as far as that first time. If you hadn’t been there you’d never know those trees suffered such trauma.

Your sycamore could have more than a mere frost crack if you find that it is approximately 10” deep. Hometown provides FREE consultation and then offers FREE quote to review soon thereafter so call us at 301-250-1033 Monday-Friday from 8am-4pm.

7-Steps To Follow When Inspecting For Tree Decay

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-Following steps were taken from an article by John Fech in the November 2012 issue of Tree Services Magazine

By itself, tree decay can be a major concern, especially if found in a soft-wooded tree species such as your silver maple or poplar. Fortunately, some species are quite resistant and if other stressors aren’t present in a significant capacity, it may not be as worrisome as other problems such as poor location, planting errors, over fertilization or drought. A step-by-step approach works best when inspecting trees for decay:

  1. Use your eyes. Look for rot pockets, oozing, weeping, conks and different colors on the bark and branches.
  2. Walk the property extensively and identify possible targets.
  3. Use your experience. Certain tree species in certain locations are likely to develop decay. Locate tree parts that could fall on a target.
  4. Look closer using probing tools: golf club, rebar or irrigation flag. Use a rubber mallet or the butt of a hatchet to tap the tree trunk where you suspect decay is present.
  5. If necessary, use invasive tools such as a resistograph or core sampler. Reserve these for important tree specimens. Consider the use of a sonic tomograph, a device that can illustrate the inside of the tree without cutting into it.
  6. Consider the potential for each tree defect to cause failure in conjunction with the proximity of an important target.
  7. Put it all together in the form of a relative hazard assessment, combining the presence and extent of the decay with other defects.

Turf and Tree Wars*

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*shared from Tree Services Magazine article by Sharon Lilly from 1/1/13

There may be a battle brewing on your property between your trees grass. Trees and turf tend to be mutually exclusive in nature; you don’t see many trees growing in the prairies or grasslands as you may have noticed that grass is not common on the forest floor.

Our urban landscapes represent an unnatural ecosystem in which we force two somewhat incompatible plant types together and expect optimum performance from each. Trees and turf compete for sunlight, water, mineral nutrients and growing space below ground. Turf roots typically outcompete tree roots and win the belowground battle. However, the dense shade of a tree’s crown can be too much competition for turf, and trees win the aerial war.

Shade leads to reduced grass density, increased root competition and increased weed invasion. There are some varieties of turf that are somewhat shade tolerant, but this may be a partial solution, because shade-tolerant grasses tend to be less tolerant of wear.

Pruning for light penetration

Pruning to increase light penetration should be considered, keeping in mind that it is not a permanent solution. An important axiom to remember is that trees will grow into the voids created by pruning. Keep in mind the old rule of thumb not to remove more than one-fourth of the tree’s foliage-bearing crown in a single pruning. If a tree is topped or thinned too much, it will be stressed and will probably produce many water sprouts (suckers) along its branches to compensate for lost foliage. This defeats the purpose of pruning to allow more light penetration.

It may help to “raise” a tree’s crown to improve light penetration. Crown raising involves the removal of lower branches, and most tree species are tolerant of this pruning practice. Crown raising, however, does not significantly increase sunlight to the turf in most cases.

Root control

Some trees have a tendency to form surface roots, which can be a major problem in lawns. Besides ruining the appearance of the turf, they can interfere with mowing equipment, and can even become a safety hazard. Homeowners always want to know to what extent they can prune or remove tree roots without bringing about the demise of a tree. Since cut roots tend to develop more roots, root pruning is usually not a good solution.

The most simple maintenance recommendation is perhaps also the most important: mulch. Mulching the root areas of trees is probably the least expensive but most beneficial thing you can do to enhance tree health and minimize competition with turf. Mulch helps retain soil moisture, moderates soil temperature, and reduces competition from weeds. Organic mulch can help condition the soil and improve microbial activity.

Apply mulch about 3 to 4 inches deep, but do not pile it against the trunk of the tree. As far as the trees are concerned, the bigger the mulched area the better. Group trees together in mulch beds and extend the mulched areas as far out as practical.

Fertilization

There is a long-standing, but inaccurate, belief that trees must be “deep-root” fertilized. This belief is associated with the myth that a tree’s root system is an underground mirror of the crown. Because most of the absorbing roots are actually in the upper few inches of soil, it makes little sense to place the fertilizer deeper.

If the lawn is being fertilized and trees are occupying the same area, the trees might not require supplemental fertilization. The key to any fertilization program is to base the application on the plant’s needs. Soil and foliar analyses can provide the information required to make an educated decision about nutrient needs.

Mowing

Mowing equipment and string trimmers can damage trees. Most people don’t realize the degree of damage that can be caused by the bumping of a mower or the whipping action of the nylon string in a trimmer. A tree’s bark can provide only so much protection against these devices. Young, thin-barked trees can be damaged almost immediately. In the worst-case scenario, the trees are eventually girdled and die. Those that are not killed will be stressed. The wounds may serve as entry points for diseases, borers or other insects. Many canker rot and root decay fungi have entered trees from wounds created by lawn and landscape maintenance workers.

Chemical treatments

Herbicides, especially broadleaf weed killers, are often used on lawns. Since most trees are broadleaved plants they can be injured or killed if high enough doses reach them. Homeowners must keep in mind that “weed and feed” fertilizers contain herbicides that can damage trees.

Achieving a balance

Trees and turf can peacefully coexist and even thrive together in a landscape. Armed with an understanding of how each affects the other, you can modify your landscapes and adjust your maintenance procedures to optimize the growing conditions for both.

Tough Locations for Trees

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Hometown Tree Experts

Even after a tree is selected and installed based on the site conditions of sun, shade, soil drainage, proximity to other trees and shrubs, nutrient availability, desired size, slope, surroundings, adjacent activity and more, it can fail to thrive.

Sometimes that’s because the tree wasn’t chosen well and sometimes it’s because it wasn’t planted well. But even more critical to the tree’s success is where it was planted. A tree’s proper location usually will determine whether it becomes an asset or detriment to the landscape.

Tried and true: RPRP

The gold standard of “Right Plant, Right Place” still reigns supreme.

Most arborists would say failure to mind this guiding principle begins with a lack of consideration for the tree’s size. Many reasons exist for this, including lack of foresight and denial that a certain species will actually get that big or wide. Many property owners are too lazy or self-centered to consider the future of their land and the potential ramifications associated with it.

The next consideration is the square footage of available rooting space required for adequate growth, nutrient absorption and structural and support. Although it’s a gross generalization, the average shade tree requires about 1,000 square feet of unimpeded surface – either covered by turf, mulch or groundcovers – in which to grow. In many locations, this much space isn’t provided.

The desired shape of tree – vase, cylindrical, rounded – also can play a role in RPRP. Some sites allow these forms to grow and develop well, and others don’t. The ones that require the largest available space are often limited on site.

The availability of sunlight is a key consideration when choosing tree species, as many require full sun exposure, while others are tolerant of, or actually prefer, shade. Species such as serviceberry, pagoda dogwood and redbud are often poorly sited as a result of this factor.

Tough sites and why

Unfortunately, many sites are compromised in one way or another. These are the most common tough sites.

Slopes: Gentle slopes are desirable; a 2 to 3 percent drop-off facilitates water movement away from buildings, yet generally allows for water movement downward through the water profile. When the degree of slope is 5 to 10 percent or greater, problems commonly arise in tree performance and landscape maintenance. At least four undesirable outcomes are associated with a severe slope:

  • Decreased infiltration rate: On slopes, natural rainfall and irrigation water isn’t absorbed as quickly as at the top or bottom. Trees growing on the face of the slope often suffer from inadequate moisture in the root zone.
  • Difficulty in mowing: When turf grass is grown on the slope, an increased chance exists for the mower to slip and slide, potentially striking the tree trunk or lower branches, causing damage.
  • Difficulty in application of fertilizers and pesticides: After landscape maintenance products are applied on slopes, there’s a tendency for them to move downward, especially when granular products are used and/or moderate to severe rainfall occurs after application.
  • Difficulty in mulch retention: Over time, mulch pieces tend to drift downward or sideways on slopes, moving away from installed landscape plants.

Hell strips: The thin, narrow and sometimes oddly shaped portions of the landscape often provide an inhospitable location for trees to grow well. The lack of available rooting and absorptive space is the main limiting influence. In northern climes, hell strips (also called tree lawns or devil strips, depending on your region) are often the space between the sidewalk and a street; in these situations, applied salt and sand for winter traction control causes damage and adds to the lack of rooting. In general, the siting of woody plants in these locations should be carefully considered.

Parking lots: Parking lots offer many of the same negative influences as hell strips. Salt, sand, radiating heat – along with the added occasional misfortune of cars, juvenile delinquents and shopping carts running into the trunk – are the major ones. The main differences between the two are that parking lots generally offer a bit more rooting space and a whole lot more interaction with pedestrians.

Middle of turf: Generally, trees and turf don’t mix. In most scenarios, turf requires more water and fertilizer than trees; in a mixed planting, if moderate amounts are applied to keep the turf thriving, excessive amounts of both are received by the trees. As well, in the midst of an island of turf, tree trunks are prone to mower blight, especially by youngsters and turf maintenance professionals who are in a hurry. The key message to deliver to them is to stop the movement of the mower before it reaches the tree, not after.

Next to concrete and rock: These materials have their place in the landscape, but it’s hard to overlook their negative impact on trees. They have a warming effect on the soil, don’t facilitate horizontal root growth as well as organic materials, provide no soil replenishment and are just so-so on moisture retention and weed suppression as compared with organic mulches and materials.

Compacted sites, high traffic spots: Settings where the soil particles are routinely compressed are tough locations for trees. Common locations for compaction of the soil are those that receive high traffic such as parks, campus grounds and shopping malls.

Adjacent to tough sites: Locations that are adjacent to the tough sites of compaction, hell strips, parking lots and other concrete surfaces may appear to be in good shape, or at least have the potential to produce healthy shoots and roots, however they are still adjoining and share a root zone. At best, sites adjacent to poor locations are half and half – half compromised and, hopefully, half conducive in terms of healthy soil, adequate space and overall growing conditions.

Close spacing: Often a scenario where the original property owner didn’t take size into account and planted way too many trees in way too small of a space. Close spacing is really an issue of trees competing for sun, nutrients and water.

Extremes of sunlight reflection: Commonly noticed when one side of a tree – the side that faces an office building – becomes blighted by excessive sunlight that can cause desiccation of the bark, stems and leaves.

Extreme shading: Opposite of sunlight reflection, absence of sunlight can cause etiolation, or a stretching for adequate light to support sturdy shoot growth. Growth that occurs in a heavily shaded location is usually thinner and weaker than when grown under ideal conditions.

So, what to do?

Identification and understanding is the first step in dealing with difficult sites; four other actions are next as making a difference in your landscape:

*First – it’s important to evaluate the status of the tree in question. Inspect for tree hazards and document defects that will influence future actions.

*Second – decide whether to keep the tree in the landscape or remove it. Consider the number of issues that weaken its structural integrity and limit the aesthetic value. If the tree doesn’t contribute toward the goals for the property, perhaps it shouldn’t remain on site.

*Third – if removal is chosen, possible replacement choices for each site can be contemplated. This is especially true for specimens that are not performing well due to an incompatibility with the size, sun, shade, soil and slope specifics of the site. For example, if a large tree is growing where a small one is called for, the potential replacements should be chosen from that group of options. In terms of possible selections for new specimens, local botanic gardens and arboretums are good places to gather information on suitability.

*Fourth – avoid planting in tough locations in the future. Seek advise on the microclimates where trees simply aren’t a good choice. In many scenarios, tall shrubs, groundcovers, perennials, native grasses and other landscape ornamentals are better options.

Tree Stress Management

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Often times, urban trees are vulnerable to pests and diseases because they are highly stressed. Stress can result from a variety of factors including the following:
-drought
-paved surfaces that interfere with water absorption
-restricted root spaces
-compacted soils
-competition from dense layers of turf that surround a tree – Note: your trees should have layer of mulch surrounding diameter – call our Hometown Landscape division @ 301-490-5577 to assist with this recommendation.

Trees are also often times planted where they shouldn’t be or can be damaged from construction or heavy equipment. There is no single solution for managing all these issues; however, Hometown Tree Experts could assess this issue to ensure improving the overall health of your trees. Research has shown that proper care can increase the fine root density, helps to reduce water loss during dry and hot periods, and could increase the protective barrier of leaves. The trees are also greener and are better able to deal with stress. Call Hometown Tree Experts for solutions to your possible stress management @ 301-250-1033.

Bacterial Tree Ooze: How To Identify

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Slime spotted on trees is known as bacterial ooze. There are different types of bacterial ooze, and they’re not very well studied. Bacterial ooze can easily go unnoticed. At its most basic they form when a tree gets damaged and subsequently infected with bacteria. In certain circumstances if the bacteria is able to feed on the tree sap and nothing prevents it from multiplying it will eventually form this slime.

Trees, like all plants, have an immune system which should protect them from severe infections like this.  Bacterial ooze happens when the tree is unable to heal a wound and prevent the bacteria from feeding on the sap. Bacterial oozes are often fatal; the ooze that forms will rot the tree as the bacteria ‘eats’ it, ultimately leading to the tree’s death.

Without knowing what bacteria is causing the problem, it’s difficult to know how contagious an ooze might be, but in most cases the ooze itself only forms when specific conditions occur on a tree so shouldn’t spread in a woodland. The bacteria involved are often present in a woodland anyway without causing any problems – the ooze forms when something goes wrong and the bacteria breeds out of control.

Bacterial oozes may be accompanied by other pathogens that further harm the tree. For example, slime flux is a type of bacterial ooze that is a mix of bacteria and yeast. It has quite a distinctive orange/yellow appearance. The yeast and bacteria ferment the tree sap, leading to an unpleasant smell and attracting insects to the ooze.

How we could help

If you spot a tree with bacterial ooze on it, we recommend that you call Hometown Tree Experts to assess. Hometown Tree Experts would assess your tree to ensure that it is indeed safe as the rot may be weakening your tree. This issue may be spreading bacterial oozes to other trees on property so would advise assessment to prevent. If you are able to provide good photos we would appreciate this photo being emailed to us as we’d love to see them!

Trees and Hedges Keeping Cities Healthy

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Hometown Tree Experts

Sulfur dioxide, nitrogen oxides, particulate matter, fluorides, carbon dioxide, ozone. What do all of these hard-to-pronounce things have in common? They are all making their way into your body when you breathe. That’s right, these air pollutants are everywhere, even when you can’t see them. In cities, there’s a mouthful in every breath.

There are two types of air pollutants: primary and secondary. Primary pollutants are toxic as soon as they are released into the air and typically have a source that can be pinpointed. The biggest threats in this category in cities are particulate matter (PM), sulfur dioxide (SO2) and fluorides. Secondary pollutants, on the other hand, form in the air from interactions whose components might not have been toxic on their own. The major secondary pollutant we find in cities is ozone (O3).

When we talk about ozone as an air pollutant, we’re referring to ground-level ozone (which we don’t like) as opposed to stratospheric ozone (which we do like) that creates a layer in the atmosphere protecting us from UV rays. Ground-level ozone is common in areas with dense populations and traffic because ozone forms when hydrocarbons and nitrogen oxides (NOx) from industry and automobile emissions interact with sunlight.

Particulate matter consists of microscopic particles from car exhaust, road dust, industry and other emissions. It is usually measured in two categories according to size: PM10, the larger kinds, and PM2.5, the smaller and more dangerous. The smaller the particle, the deeper into your lungs it can travel, and once it’s down there, it stays there. This leads to respiratory illnesses like asthma and lung cancer — outdoor PM causes 3.2 million deaths every year worldwide. SO2 and fluorides are produced by fossil fuel combustion, which of course there’s a lot of in cities.

With the known health consequences of respiratory illness, cardiovascular disease, and lung cancer, it is clear that we should avoid exposure to these toxic air pollutants, but we don’t always have a choice. People in cities are especially vulnerable, since they have such frequent exposure to high concentrations of them. According to the World Health Organization, concentrations of PM exceed safe levels on the streets of more than 600 U.S. cities. Thankfully, city trees and greenery offer the beginnings of a solution to urban air pollution.

A study in London linked the annual removal of 90.4 tons of PM10 by urban trees to a decrease in 2 deaths and 2 hospitalizations per year. And according to a study in the U.S., the amount of PM2.5 removed annually by trees in 10 cities across the country in 2010 ranged from 4.7 tons in Syracuse to 64.5 tons in Atlanta. In the same cities, estimates of the annual monetary value of human health effects associated with PM2.5 removal, such as hospital admissions, respiratory symptoms and related deaths, ranged from $1.1 million in Syracuse to $60.1 million in New York City. That’s right: trees save lives and money.

Strategic placement of grass, ivy and other plants in cities can reduce the street level concentrations of NO2 and PM by 40 and 60 percent, respectively. There are multiple ways trees help to make urban air cleaner by filtering out pollutants:

Temperature reduction

Lowering temperatures reduces the movement of harmful ambient particles and prevents more pollutants from evaporating into the air. Trees create a great cooling effect by shading homes and streets, breaking up urban heat islands, and releasing water vapor into the air through their leaves. More tree crowns mean less dark surfaces like parking lots and paved streets being exposed to sunlight and emitting heat. Tree canopy cover in Los Angeles has decreased over the last 50 years, and a corresponding 6°F increase has been measured. Depending on the tree placement, trees can cool a city by up to 10°F, reducing the concentration of PM and other air pollutants with each degree.

Removal of pollutants

The first way trees remove air pollution is by particle interception: trapping pollution particles on their leaves and bark. Once the particle has been removed from the air, it is usually washed off the tree by rain or falls onto the ground with leaves and twigs. Studies have shown that in one urban park, tree cover removed 48 pounds of PM, 9 pounds of NO2, 6 pounds of SO2 and 100 pounds of carbon — daily. Silver birch trees in particular have been studied for their particle interception abilities: They have been found to reduce concentrations of PM by more than 50 percent.

A more complex way that trees filter the air is through gas uptake by leaf stomata. The stomata are tiny pores on tree leaves, and they absorb air to collect CO2 in order to perform photosynthesis. During that uptake of air, they also absorb gaseous pollutants in the air. Once inside the leaf, the gas diffuses throughout the leaf’s pores. It is then absorbed by films of water inside the leaf where it will either form acids or react with inner-leaf surfaces to become less toxic. It is estimated that one tree can absorb almost 10 pounds of polluted air through its leaf stomata every year.

Energy effects on buildings

Now that we understand trees’ chemical abilities, we can factor in their physical ones. Trees shade buildings in the summer and block winds in the winter, so it makes sense that they reduce building energy use for both heating and cooling purposes. Minimizing energy needs lowers the amount of fuel combustion necessary and therefore reduces the amount of pollution from power plants entering the air in the first place.

Once seen as an aesthetic window dressing, trees have never seemed as important in cities as they do now that we know their full potential. We can’t decide to stop breathing when we walk down a city street, but we can decide to plant and maintain healthy trees and hedges in cities to support the cause for greener cities. The air we breathe is a little bit cleaner thanks to each and every tree. Let’s keep it that way.

Benefits of Trees

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Hometown Tree Experts

Public Health and Social Benefits

Air Cleaning: Trees produce oxygen, intercept airborne particulates, and reduce smog, enhancing a community’s respiratory health. The urban canopy directly contributes to meeting a city’s regulatory clean air requirements.

Access to trees, green spaces, and parks promotes greater physical activity, and reduces stress, while improving the quality of life in our cities and towns.

  • Urban landscaping, including trees, helps lower crime rates.
  • Studies show that urban vegetation slows heartbeats, lowers blood pressure, and relaxes brain wave patterns.
  • Girls with a view of nature and trees at home score higher on tests of self-discipline.

Environmental Benefits

Climate change: Trees sequester carbon (CO2), reducing the overall concentration of greenhouse gases in the atmosphere. Read more about trees and climate change here.

Energy conservation:

  • A tree is a natural air conditioner. The evaporation from a single tree can produce the cooling effect of ten room-sizes, residential air conditioners operating 20 hours a day.
  • Acting as a natural air-conditioner, lush tree canopies ensure that summer temperatures are at least 6 to 8 degrees lower than in comparable neighborhoods without trees.
  • Tree windbreaks can reduce residential heating costs 10-15%; while shading and evaporative cooling from trees can cut residential air-conditioning costs 20-50%.

Water filtration and retention: Urban forests promote beneficial water quality and reduce storm water management costs.

  • Street and park trees can intercept 135 million gallons of rainwater. Trees capture and slow rainfall and their roots filter water and recharge the aquifer. Trees reduce storm water runoff, which reduces flooding, saves city storm water management costs and decreases the flow of polluted water into the Bay.

Wildlife habitat: Trees provide important habitats for numerous bird, insect and animal species.

Economic Benefits

Communities and business districts with healthy tree-cover attract new residents, industry, and commercial activity.

  • Homes landscaped with trees sell more quickly and are worth 5% to 15% more than homes without trees.
  • Where the entire street is tree-lined, homes may be worth 25% more.
  • Trees enhance economic stability by attracting businesses; people linger and shop longer when trees are present.
  • Where a canopy of trees exists, apartments and offices rent more quickly and have a higher occupancy rate; workers report more productivity and less absenteeism.

Tree Benefit “Fun Facts”:

  • Trees provide inviting and cool areas for recreation and relaxation such as playgrounds and parks.
  • Trees create a tapestry of color and interesting form that changes throughout the year.
  • The color green is calming and relieves eye strain.
  • Trees screen unattractive views and soften the harsh outline of masonry, metal, asphalt, steel and glass.
  • People walk and jog more on shaded streets, which encourage interaction with neighbors and improve the sense of community.
  • Trees absorb and block sound, reducing noise pollution by as much as 40 percent.

 

Inspecting for Tree Decay

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Roll-off services

Odd-shaped growths on a tree trunk are good indicators of internal decay. Tree decay is one of those inevitable things in life. By itself, decay can be a major concern, especially if found in a soft-wooded tree species such as silver maple or poplar. Fortunately, some species are quite resistant and if other stressors aren’t present in a significant capacity, it may not be as worrisome as other problems such as poor location, planting errors, over fertilization or drought.

Decay is risky

When considering overall risk analysis of a mature tree, a basic formula can be used to determine how much risk is posed by each specimen. Risk equals the probability or likelihood that a particular tree will fail times the consequences of the occurrence. The presence and extent of the decay is just one of many factors that lead to tree failure along with the tree’s ability to compartmentalize and slow its spread. The capacity to predict tree failure is limited, however, when many defects (root girdling, compacted soils, leaning, codominant leaders, cracks, etc.) are involved, the potential is greater.

Targets

The second part of the equation, the consequences of failure, can be estimated by observing the specific site details such as nearby parking lots, homes, commercial buildings, bike paths, driveways, school activity and churches. Simply put, any human presence or property of significant value creates a “target.” The consequences of failure are largely tied to potential targets, in that trees or tree parts that could cause their loss are directly dependent on their nature. Trees near important targets such as those mentioned have a high degree of potential loss, whereas trees growing in the middle of pastures are concerning only if failure occurs at the same time a high-value cow is paying more attention to the forages than to a falling limb.

Hazards versus negligence

All trees carry some degree of risk. A hazard exists when a reasonable level of injury threshold has been surpassed. In this case, we’re talking about tree decay as a hazard. If a small amount of decay is present, which is common for smaller trees or trees with a slow rate of spread potential, then it’s a low hazard and classified as something to monitor. If extensive decay is present and notable in rot pockets, in cracks, etc., then the level of threshold has been surpassed and a distinct hazard exists.

You have a duty to provide reasonable and proper care for trees. Negligence occurs when you have failed in that duty, and the failure has caused injury that caused real harm to people and/or property. In the specific defect of tree decay, ignoring or delaying action when a substantial amount of decay is present could be considered negligence.

Regular and thorough inspection

In order to prevent damage to people and/or property, it’s important to perform regular and thorough inspections. How often is regular? The answer is – to a certain extent – it depends. If your property has targets (most of them do), then inspections should be made more frequently than if no targets exist. The frequency also depends on the tree species. Decay-prone tree species should be inspected more frequently than those that naturally resist decay such as walnut, Osage orange and black locust.

Another part of the answer is frequency of use, somewhat involving the existing targets. For example, if the grounds of a cemetery contain a large number of mature trees, a target-rich environment is probable. While the target is high, in this case the frequency is low, as 90 percent of visitors pay their respects to the departed on Memorial Day and Veterans’ Day. The opposite is true for shopping malls and campus grounds, where lots of people are present during the day, and there are also lots of high-value property targets. On these sites, the desired frequency is perhaps not weekly, but monthly wouldn’t be out of the question. Bottom line: On high-value sites with significant targets all mature trees should be inspected for the presence of decay at least seasonally.

Inspection technique

Inspectors who have studied trees for many years have most likely have had the opportunity to work with hundreds of professionals and scientists and would find that each one has a slightly different methodology to determine whether or not decay is present. Though it’s hard to say if one is more effective than another, short of cutting a tree down and slicing it into wood cookies, a step-by-step approach works best when inspecting trees for decay.

  1. Use your eyes. Look for rot pockets, oozing, weeping, conks, and different colors on the bark and branches.
  2. Walk the property extensively and identify possible targets. Interview the property owner and neighbors to get a handle on the frequency of use on the site.
  3. Use your experience. Certain tree species in certain locations are likely to develop decay. Locate tree parts that could fall on a target.
  4. Look closer using probing tools: golf club, rebar, and irrigation flag. Use a rubber mallet or the butt of a hatchet to tap the tree trunk where you suspect decay is present.
  5. If necessary, use invasive tools such as a resistograph or core sampler. Reserve these for important tree specimens. For example, inspecting an oak at the entrance to the “Harvard Oaks” subdivision or a memorial tree. If the property owner has plenty of money to spend on inspection, consider the use of a sonic tomograph, a device that can illustrate the inside of the tree without cutting into it.
  6. Consider the potential for each tree defect to cause failure in conjunction with the proximity of an important target.
  7. Put it all together in the form of a relative hazard assessment, combining the presence and extent of the decay with other defects.