Living in a condo in the city of Chicago, I do not have much outdoor space to grow trees and other plants. However, I am lucky to have a roof deck on which I have grown a wide variety of plants. With some careful planning, you can grow almost any plant on a roof deck, including trees. If grown successfully, you’ll love the benefits of mid-summer shade and simple addition of nature trees bring to your roof living space. Here are some considerations for successfully doing so:
1.Mature Tree Size
Be sensible on your species selection, and make sure to choose only small to medium sized trees. You shouldn’t be planting a red oak on your roof deck, for example, as it wants to get over 100 feet tall. As a tree grows, it not only takes up more space on your deck but also requires more water and nutrients. You will have to consider how wide the branches will get, so that you won’t have to prune them back from walkways and seating areas multiple times per year.
Heavier containers (wood, clay, etc.) are a better choice for rook decks than plastic as they are more resistant to tipping over in strong winds. Planting multiple trees in one large container is better for your trees that individual small containers. In a large container, trees can share rooting space and soil.
Your roof deck likely gets a LOT of sunlight. My deck gets basically 100% sun exposure. Therefore, you’ll need to select plants that are adapted to such sunny conditions. Choosing shade-loving plants can lead to severe water shortages and foliage scorching, which can lead to other tree health problems in the future. Another consideration is that, so long as you provide your trees with their needed water and nutrients, the excessive sunlight on your roof deck will cause your tree to have more substantial growth year over year than trees of the same species grown on the ground,
Your roof deck trees are going to need a lot of water. If your deck is like mine, it has 100% sun exposure. That means trees will need use up a lot of moisture every day they are leafed-out. You’ll need to provide water to your trees even when they don’t have leaves. You will need to determine where you’ll get water from for your plants. The source will likely be a hose-accessible spigot or water from a faucet inside your home.
I do not have water access on my roof, so I am forced to carry multiple gallons up from my condo. I sometimes have to do this 3 times per day on a hot mid-summer day. You can also purchase or engineer self-watering containers that will at least store a moderate amount of water.
You’ll need several inches of soil to support fulling grown trees in containers. Small trees need a depth of at least 1 foot, and medium trees will need about 3 feet. The available soil should be at least 4 feet in diameter for small trees and 8 feet in diameter for large trees.
Place a few inches of natural mulch on the tops of your containers to help with nutrient cycling. Mulch will also help to keep the containers from drying out as quickly.
Soil is the heaviest component of a roof deck planting system. No matter the size of containers or the amount of soil you use, make sure your roof can handle the weight. For containers supporting large trees or those covering more than a few square feet of your roof, you should consult with a structural engineer to make sure your roof can handle the additional weight.
You will need to consider the temperature of your specific roof deck, not just the surrounding area. Your roof deck is likely quite exposed to the wind. This can be especially concerning in winter.
As you can see, there is a lot to consider when trying to grow trees on your roof deck. However, with some thorough planning (and a LOT of watering) you can grow a wide variety of trees and other plants that will help make your outdoor space more enjoyable.
Should I Fertilize My Trees?
Urban trees grow in an environment often quite different from their rural cousins. They are generally growing in places where they have not evolved to adapt. Roots grow under pavement. Road salts damage leaves and root systems. Vandals tear off branches and uproot entire trees. Construction compacts soil and tears roots.
Because of the environment in which they grow, urban trees often need our help. Their genome cannot anticipate all that people and cities will throw at them. The entire field of arboriculture is based off the fact that trees are growing in a human-impacted, not-natural-to-the-tree environment. However, the type of help they receive should be based on the needs of the tree, given its species and actual site conditions. Fertilization is often prescribed by tree care companies as one such remedy to improve tree health. However, such a prescription is often unwarranted.
Fertilization and other soil remedies should never be prescribed without diagnosis. Doing so is a waste of money and can lead to environmental problems such as elevated nutrient levels in waterways. Fertilization is useful in some cases, however. But there is only one reason why your trees should ever be fertilized –
Trees should only be fertilized because of a documented soil nutrient-tree need mismatch, which can be improved through the addition of deficient nutrients.
Unfortunately, many tree care companies prescribe fertilization without so much as doing a soil test. There is a simple, likely-obvious reason why they do this – it makes them a LOT of money. Never agree to have your trees fertilized if your tree care professional has not performed a soil test. If an arborist even suggests fertilizing trees or other soil amendments without a soil test, look elsewhere for help with your trees.
There are many other reasons why an arborist may suggest fertilizing trees. Some reasons that are insufficient for prescribing fertilizer include:
1.Trees are newly planted
You should never fertilize trees simply because they are newly planted. Some studies show that fertilizing newly planted trees can impede root growth, and lead to unhealthy top growth.
2.Tree roots have been damaged
A common reason for fertilizing trees is to help improve tree condition after root damage. However, the only way to help recover from root damage is to improve root growth. Fertilization does not aid in root growth, but can often impede such recovery.
3.Soil pH issues
If the trees on your property need nutrients in greater amounts. In this case, soil pH remedies would be a better option. However, the efficacy of such treatments is questionable at best.
As is the case with many aspects of arboriculture, the best answer to the problem is to plant the right tree in the right place. A tree species adapted to the soil conditions present on your property will often eliminate the need to fertilize at any point in the life of the tree. It can also eliminate the need to use other nutrient deficiency correcting solutions as well. Again, if your arborist or tree care professional prescribes fertilization or other soil remedies without a soil test, look elsewhere for help with your trees.
Watch that Lean
A leaning tree is not necessarily a cause for concern. If a tree has been leaning for most or all of its life, it has likely put on wood in the right places to adapt to the lean. Trees may lean in response to surrounding trees, available light, simple genetics or other reasons.
If you notice things like a change in lean, soil heaving around the base of the tree or cracks in the stem the tree should be further evaluated. If you are concerned about any leaning tree, have an arborist perform an inspection.
Branches of Failure
Trees with a large number of branches originating from one location can be prone to failure. Such branches have weak connective tissue and branch angles that have difficulty supporting branch weight. When these branches do fail, they often lead to large wounds that the tree has difficulty closing.
Ideally, such a problem would be fixed when the tree is very young. Most deciduous trees should be pruned so that a single leader grows from the top of the tree, at least when young. It gets difficult to prune the tree correctly when it is larger, because the pruning cuts will be larger. Such cuts can be difficult for the tree to close and can lead to decay issues. The best solution is to plant trees not prone to such branching.
Surface Root Problems
Surface roots can lead to problems such as root desiccation, lawn mower damage and trip hazards. They are often a sign of water and soil issues in a property.
Matching a tree to the site is the best way to prevent this, but once it occurs it can be alleviated with the careful application of soil and mulch.
Tar spot of maple is a leaf disease that shows up every year. And like every other year, people worry that their maple trees are sick or dying. Luckily, tar spot is a disease that looks much worse than it actually is.
It is showing up early this year, likely due to the rainy spring we had in northeast Illinois. Right now it is in the early stage, where the spots are yellowish with black specks in them that may go unnoticed. As the disease develops, the spots will look just like shiny black spots of tar flung about on the upper surface of maple leaves. The spot most commonly infects leaves of silver and Norway maples, although red and sugar maples are also susceptible.
It does little harm to the trees, but is unsightly. While it is only July, maple trees have already received the majority of the functionality they will get all growing season from their leaves. Therefore, some lost leaves will not do much harm to the tree. Fungicide/chemical treatments generally are not necessary. To reduce inoculum, rake up and discard the leaves in fall.
Below is a step-by-step example of a tree appraisal I recently performed using the Trunk Formula. This is used to determine the value of trees too large to replace. To read ore about tree appraisal and valuing trees in general, check out our article on the subject.
I was retained to appraise a 22-inch diameter Bur oak (Quercus macrocarpa) in Naperville, Illinois.
In order to determine the value of the tree, I utilized the trunk formula method as outlined in the Council of Tree and Landscape Appraisers Guide for Plant Appraisal, 9th edition. The trunk formula is the best method for appraising individual trees that are considered too large to replace with container or field-grown stock. Determination of the value of a tree is based on the cost of the largest commonly available transplantable tree and its cost of installation, plus the increase in value due to the larger size of the tree being appraised. These values are adjusted according to the species of the tree and its physical condition and landscape placement. Detailed calculations can be found at the end of this report.
The detailed trunk formula is as follows:
Appraised Value = Basic Tree Cost X Species% X Condition % X Location %
Basic Tree Cost = Trunk Area Increase of appraised tree X Unit Tree Cost + Installed Tree Cost
Location = (Site % + Contribution % + Placement %)
Basic Tree Cost
The basic tree cost is determined by comparing the cost of installing the largest commonly available transplantable tree of a high quality species to the size of the appraised tree. This cost is typically published by a regional committee or state chapter of the International Society of Arboriculture. Given the site's location in Naperville, Illinois I utilized the cost determined by the Illinois Arborist Association (IAA).
According to the IAA, the cost to be used is $787 for a 4-inch caliper tree. The cost includes transportation to the site, site preparation, planting, guarantee and profit. The unit tree cost to be used for the transplantable tree is $71 per square inch of trunk cross section.
Trunk Area Increase = (22*22*0.785) – 13 = $366.94
Basic Tree Cost = $366.94 * 71 + 787 = $26,839.74
A species rating guide is published by the IAA as well. Species ratings are based on species characteristics, without regard to condition or location. Factors considered in determining species ratings generally include environmental adaptability, biological traits, maintenance requirements and aesthetic characteristics. I utilized species rating guides for Illinois. Based on the IAA guide bur oak has a species rating of 90%.
Species rating = 90%
Condition rating takes into account the condition of the tree's roots, trunk, scaffold branches, small branches and twigs and foliage and/or buds. The condition is rated on a scale of 0-32, as follows with my ratings:
Roots (2-8) – 5
Trunk (2-8) – 6
Scaffold branches (2-8) – 5
Small branches (1-4) - 3
Foliage (1-4) – 3
I have thus assigned 22/32 points for tree condition based on my observations.
Condition rating = 68.75%
Location rating takes into account the overall site rating, which I have determined to be 80%. This is then compared to the tree's individual placement in the landscape and its contribution to the landscape to determine an overall location rating. I have assigned the tree a placement rating of 80% and a contribution rating of 80%. These are determined by what benefits the tree adds to the property, and how its placement affects these benefits. Benefits include providing shade, blocking the view of neighboring properties and intercepting rainfall.
Location rating = 80%
Appraised Value = Basic Tree Cost X Species% X Condition % X Location %
$26,839.74 X 90% X 68.75% X 80% = $13,286
When the appraised value is $5,000 or more, the value is rounded to th nearest $100. When it is below $5,000 it is rounded to the nearest $50.
Appraised value = $13,300.
This week I was called to inspect the yard of a homeowner who was concerned and upset about a vine that had come to nearly take over her yard over the last couple of years. The vine, Virginia creeper (Parthenocissus quinquefolia) had invaded her yard from the neighboring yard to the northeast, and covered most of her shrubs. It appeared that the vine was taking over plants in at least 3 other neighboring yards as well.
Controlling Virginia creeper can be quite a pain if the plant has been allowed to grow for an extended period of time, but removal is still possible.
Remove While Young
Obviously this is only possible when the plant is actually young and small. But be on the lookout for small patches of it in your yard. Removing it early on will make your life much easier, and save you the pain of having to cut the vine away from you and your neighbor's properties.
Cut it Back
If the plant has grown to significant size you will likely have to do a lot of cutting to get rid of it. Start by finding where the vine is rooted, and cut at the base plus the next several feet above the soil line. It is good practice to remove the vine from neighboring plants as well to prevent any negative effects on growth and will help improve appearance.
After you have removed as much of the vine as physically possible, apply herbicide (Glyphosate, preferably). If you do not apply herbicide, the vine is likely to come back quite quickly, especially if it had been growing for a significant amount of time and had produced a sizable root system. Make sure to follow all labeling instructions for application rates and personal protective equipment.
With the onset of fall comes tree planting season. Along with that comes the inevitable questions of what tree should I plant and where should I plant it? You want to choose a tree that will grow well and meet the needs and goals you have for your property. The three tools below can help you do that, no matter where you live.
1. National Tree Benefit Calculator
Start with this tool to see what benefits the trees currently on your property are providing. This tool calculates economic and ecological benefits such as tree dollar value, energy savings and carbon sequestration among others. It is helpful to know what benefits your trees are currently providing so that you can fill the benefit gap with new trees.
You can find the calculator at www.treebenefits.com
2. Tree Species Selectors
There are many factors to consider when planting a tree - mature height/spread, soil needs, climate, fruiting, aesthetics, etc. You want your newly planted tree to survive to maturity, and likely have some goals in mind for what the tree will provide. You simply put in the variables (or as many as you know) and the selector spits out a list of trees suitable for your planting location.
You can find a number of tree species selectors in our Resources section.
3. i-Tree Design
i-Tree Design will help you place trees around your property to maximize the benefits they provide. The tools uses mapping and your building's footprint to determine tree placement. The tool then tells you what your new tree will provide in terms of greenhouse gas mitigation, air quality improvements and stormwater interception. You can play around with a few different species and locations to determine what works best for you and the environment.
You can find i-Tree design at www.itreetools.org/design.php
What's Up With My Maple?
Over the past few weeks, I have fielded several calls from clients and concerned homeowners about the condition of their maple trees. Some are worried that their trees are dying, or that they will at least lose all of their leaves way too early. They explain that the leaves have large black spots all over and that many leaves have dropped suddenly over the past few days.
While I can understand the initial concern over the sick-looking appearance of their tree, luckily the tree generally looks a lot sicker than it actually is. What is typically affecting the tree is a leaf fungus called tar spot. Tarspot, of the genus Rhytisma, is a very common disease of maples that is currently widespread throughout the Chicago area. The disease manifests itself as dark spots on leaves that resemble tar. While the disease can be aesthetically unpleasant, infections are rarely a serious threat to the health of the tree. Heavy infections can cause early leaf drop, but even in this case defoliation typically occurs too late in the growing season to be a serious concern.
Treatment of leaf spot is not recommended. While there are fungal applications available, they are not considered worthwhile as their effectiveness is very limited. This, combined with the fact that the disease is not considered a major health concern mean that treatments are not recommended. The best thing to do is to keep the tree healthy in other aspects. The disease is also very weather-dependent, so infections are heavier in some years than others.
So if your maple has leaves looking like the one in the picture above, don't be too concerned. Just keep the tree happy and hope that next year isn't such a heavy year for the disease.
i-Tree is a software suite from the U.S. Forest Service that provides urban forest analysis and benefits tools. i-Tree helps quantify the structure of trees and forests to determine the benefits that trees provide. i-Tree Canopy is a tool within i-Tree that is used to provide a basic, but useful assessment of the tree canopy in a given area.
The i-Tree Canoy process involves the following:
Tree canopy and benefits are then estimated by i-Tree based on the results of the analysis.
I utilized i-Tree Canopy to assess the tree canopy within the Buena Park neighborhood of Chicago, in which I live. The map below shows the boundary of Buena Park, along with a few of the sample points used in the analysis. I included only the parts of the neighborhood west of Lake Shore Drive, as these are the inhabited portions.
Tree Canopy Percentage
i-Tree Canopy analysis showed that about 16.6% of Buena Park is covered in tree canopy, This is below the average of 21% for the entire Chicago region determined through a 2013 study, This is not too surprising, since the whole-Chicago study included dense urban areas like Buena Park but also more natural areas such as forest preserves. 16.6% canopy is therefore respectable given the urban nature of the neighborhood, and likely higher that most other areas in the city of Chicago.
Tree Canopy Benefits
Other benefits of urban trees measured by i-Tree Canopy include carbon sequestration, ozone removal and particulate matter removal. The total benefit for each of these, measured in amount removed and dollar value, is below:
Carbon Dioxide sequestered annually in trees - 148.66 tons ($5,378.80)
Carbon Dioxide stored in trees - 3,748.16 tons ($135,632.54)
Ozone removed annually - 1,460.18 lb ($102.19)
Particulate Matter less than 2.5 microns removed annually - 70.95 lb ($211.25)
I plan to further study the tree canopy of Buena Park to determine available public and private tree planting spaces, as well as ideal location for future tree planting. My goal is to determine the best places to plant trees in the neighborhood to maximize the return on investment of tree planting funds.
When I tell new acquaintances what I do for a living, they often ask me how I got into the field of urban forestry. The truth is - I gained an appreciation for trees and the environment at an early age. While growing up, I spent many hours in the woods, lakes and parks of central and northern Wisconsin. I hunted, fished, rode my bike, sat by a lake, and took part in many other outdoor activities. Doing so led me to appreciate the benefits that nature and trees bring to people - beauty, clean air, solitude, among others. As a kid I always had it in my head that I would focus my future career on the environment somehow.
I applied to only one school for undergrad the University of Wisconsin - Stevens Point and its College of Natural Resources. When I first got to UWSP I became a wildlife management major, having pictured myself saving habitat for wildlife in some remote location. I soon switched to Urban Forestry however, as I thought it would offer me more of a chance to manage natural resources in urban areas where I thought I could have more of an impact. Hearing that the job prospects and potential income were better didn't hurt.
After graduating from UWSP I became an arborist for many of the same reasons I switched my major back years earlier. I have (mostly) remained in the field for the last 11 years. While I have held multiple jobs, my positions have always focused on conserving trees and other natural aspects of urban areas. More than one person has expressed jealousy that I have been able to follow my passion from childhood through my early 30s.
I often present the environmental benefits of trees to clients and audiences in terms of dollars saved by our urban forests, carbon sequestered, pollutants removed, etc. And while all of that is well and good, if the audience member doesn't have a personal connection to the nature they are hearing about I highly doubt they will take what I am saying to heart.
Richard Louv's book Last Child in the Woods is probably my favorite piece of literature that explains how important it is for people to experience nature while they are young. If I hadn't spent so much time in the outdoors as a kid, how could I possible appreciate the benefits that all things wild and free provide?
So let your kids play outside. Take them camping, fishing and hiking. We'll need many more urban foresters and related conservation professionals in the future.
It's the arborist's fault if tree issues aren't considered during construction and other development projects.
That's the mantra I follow when working on tree preservation projects. After all, if the arborist doesn't speak for the trees, who will? Someone else concerned for saving trees might speak up, but without the backing of the so-called expert, trees in the way of construction stand little chance. In working to preserve trees during construction, the arborist generally has one of the following roles:
1. Tree Advocate
As mentioned above the arborist is expected to stand up for trees on a development project. It is often assumed that if the arborist does not stand up for trees, then they must not be worth standing up for. Sometimes (often) being a tree advocate means determining which trees to remove. While being a tree advocate, the arborist must also be realistic and not attempt to preserve trees that unrealistically h old up development or that will not survive construction.
2. Specialist, but also a generalist
Wwhile teh arborist is responsible for tree-specific issues, they also must understand other disciplines and how they affect trees. Urban planning, building construction, municipal government, soils, hydrology - alll of these must be considered in determining how (or if) to preserve trees.
The arorist has to be able to communicate and work with others on the project team. The general contractor, landscape architect, property owner, governing body and others will all be involved. These actors expect the arborist to be able t o work with them, communicating issues in a clear way.
Many people see trees as something nice to look at, but also something that can be easily disposed of if they become a minor annoyance or stand in the way of development. It is the arborist's job to educate on why trees must be preserved. Tree preservation is not just about saving pretty trees, t is about maintaining the many other benefits that trees bring to our urban environment. Increased property value is often the one that resonates the most with people, but slowed runoff, wildlife habitat, reduced urban heat islands, carbon sequestration, improved human health and pollutant removal are good ones too!
5 Keys to Planting a Tree
Planting a tree seems like and can be a pretty simple process. However, if you think through a few factors before selecting and planting a tree, you give it the best chance to succeed and add benefits to your property for decades to come. Here are a few tips.
1. Match species to site
Make sure the tree is cold hardy for your region. Check your soils to determine if there will be a nutrient/pH incompatibility before planting so that you won't have to correct it later. Look at what trees do well in your area.
2. Leave space for growth
Trees grow, of course, but it seems that people sometimes forget about this. I recently completed a management plan for a homeowners' association in Illinois where about 300/1000 trees have outgrown their space only 10 years after planting. Trees don't give us much benefit until they reach maturity, so give them the space to do so!
3. Inspect for defects
Examine the tree at the nursery or garden center. Look for the following:
Good form - does it have a good central leader? Broken branches?
Signs of disease/insects
Healthy root flare
Basically, start with a healthy tree to minimize problems later.
4. Proper planting hole
Dig the hole just deep enough to plant the root ball or bare roots. The root flare should sit a couple inches above grade once planted. Dig the hole about 3X the root ball width. Backfill with soil of similar texture to the surrounding soil.
5. Post planting care
Make sure to water the tree regularly after planting. A lack of water is the number one reason why newly-planted trees don't survive.
You should also place mulch around the base of the tree, but not touching it. Mulch against the trunk can lead to rot on the trunk and root problems down the line. A 3-4 inch layer of mulch is best. Replenish as needed.
Only stake the tree if it can't stand on its own, or if vandalism is a concern. If you must stake, remove it after one growing season.
This week I evaluated a number of trees affected by emerald ash borer in the suburbs of Chicago, which reminded me of a guest blog post I wrote a few years back for a colleague's website. It covers a little bit about my past and my thoughts on the future effects of EAB around Chicago.
I developed an appreciation for trees and the environment at an early age. I grew up spending countless hours in the woods, lakes and parks of central and northern Wisconsin. Doing so led me to appreciate the benefits that trees bring to people - beauty, clean air and attraction of wildlife, among others.
Having now lived in Chicago for about 9 years, I have realized that many of my fellow urbanites didn’t have as much opportunity as I did growing up to experience nature. While many of my fellow Chicagoans do value the environment a great deal, it seems that this value has come from a different source. I believe that people begin to appreciate the environment for one of two reasons – they spend time in the outdoors and develop appreciation through their experience or they witness or learn about some sort of environmental degradation. Many Americans, especially urbanites, seem to get this value from the latter.
One such environmental challenge upon us today is the emerald ash borer (EAB). As most people reading this probably already know, EAB is an exotic insect that has destroyed millions of ash trees in North America and threatens to destroy millions more. It was first discovered affecting ash trees in Michigan around 2002, and has since spread throughout the U.S. and Canada. Many scientists predict that the borer could wipe out ash trees throughout North America, in both urban and rural areas. This is mainly a man-made tragedy, as the pest was most likely introduced to the United States in shipping containers from the Far East. When it came aground, it found a plethora of trees that had no natural resistance to it.
While emerald ash borer may decimate ash trees in our urban and rural forests, we need to look at this event not for the damage it will cause but for the opportunity it presents. I believe that, through increased awareness and improved management, our urban forest could be better off as a result of emerald ash borer. Yes, the damage caused by this insect will be catastrophic. But if it causes people to look at the underlying causes of the tragedy and try to prevent similar events from happening in the future, then we could be better off as a result. The attention the borer is getting could also cause many people to gain greater general appreciation for trees and the environment as a whole.
It is often said that modern urban forestry was borne out of a tragedy similar to EAB. Dutch elm disease killed millions of elm trees in this country, beginning in the 1930s. Many cities saw almost their entire tree canopy lost to the disease. This mass loss of trees made people appreciate their trees once they were gone, and led many to realize that we should care for our trees before such a tragedy could strike again. However, while the disease led to increased management and awareness of the benefits of our urban forest, we did not completely learn the lessons the epidemic should have taught us. We still took care of our trees in a way that allowed devastating events such as EAB to occur.
You may ask what you can do to manage EAB on your property or in your neighborhood. High value ash trees that aren't infected or haven't begun to show much stress from the borer can be treated and potentially saved. However, it isn't economical to save many ash trees. Most will be lost. Instead, the best thing you can do is plan for the future. Use EAB as an opportunity to show why and how we should prepare our urban forest to be resilient against similar pests in the future. Many people have already begun to do exactly this. You can get more detailed information on management options at www.emeraldashborer.info.
I became an arborist because of my love for the environment and my desire to educate others about the natural aspects of cities and to improve the relationship between nature and city. I see the presence of emerald ash borer as an opportunity to do just that. Let’s continue to treat the issue as a chance to better our urban forests, parks and urban areas in general. Plant more trees. Educate your neighbor on emerald ash borer and the benefits of trees and other environmental assets.
Let’s hope that in the future we won’t need to rely so much on environmental hardships to get people to appreciate the natural world around them. But until then, let's use opportunities like EAB to help people appreciate the environmental assets that surround them every day.
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There are many reasons to preserve during construction, including legal requirements, aesthetics, property value and ecological benefits. However, in order for a tree to be considered “preserved” it must survive construction and thrive for many years afterward. In order for trees to be preserved, there are five steps that should be followed:
1. Planning Phase
The planning phase takes before any site disturbance. Trees and the overall site are assessed so that construction and preservation decisions can be made. Accomplishments during this phase include:
Site survey showing all relevant features:
Tree Resource Evaluation
2. Project Design
During this phase, initial construction documents are developed, and a tree preservation plan is developed to consider trees based on construction plans. Specific steps during this phase include:
Tree preservation plan components include:
During this phase, the trees and site are prepared for actual construction activities. Accomplishments during this phase include:
The construction phase is where actual site disturbance and building construction occur. The construction phase is where physical tree impacts are most likely to happen. Accomplishments during this phase include:
-Root collar covered by fill soil
This phase includes the time period after building construction and most site disturbance is complete. Steps to this phase include:
As can be seen, there are many steps to preserving trees during construction. However, the effort is worth it to preserve trees that bring significant benefits to a property. In order for trees to be properly preserved, an arborist must be brought in to a project in the project planning phase. If trees aren’t considered until later phases of construction, it will likely be too late to properly protect them and allow trees to survive and thrive.
Tree Risk Assessment - Analyzing Tree Health and Safety Through a Standard Method
Today I had the opportunity to evaluate a honeylocust (Gleditsia triacanthos) for a client that was concerned about the health and safety of the tree. The client was concerned about the tree because it seemed to have decay in its stem and was in close proximity to a driveway and parking lot.
To evaluate the tree, I performed an ANSI A300 Level 3 Advanced Risk Assessment. This assessment included a ground-level inspection of the tree's crown, base and trunk plus surrounding site conditions. Resistance-recording drilling was performed to analyze trunk decay. Such an assessment details tree characteristics and then compares the likelihood of tree failure to the likelihood of damage from failure to assess overall risk.
TREE AND SITE CHARACTERISTICS
The tree measured approximately thirty inches in diameter at a height of 4.5 feet, which is the standard height for measuring tree size.
The tree had a wound in the trunk at a height of six feet on the east side where an old stem was removed. The wound measures approximately sixteen inches by sixteen inches. There is an old pruning wound at twelve feet. There is little to no callus wood around the wounds. Callus is a type of wood that forms in response to wounds in an effort by the tree to seal off the wound. A lack of callus indicates stress in the tree. A fruiting body had been previously removed at a height of three feet on the north side of the tree, which could possibly indicate internal decay.
The tree is approximately 35-40 feet in height. The crown is somewhat one-sided to the east. The tree's leaves appeared green and healthy overall, with only a small amount of dead limbs present in the crown. A small number of leaves have damage from leaf chewing insects, but this damage does not appear severe enough to significantly affect tree health.
The tree is somewhat mature. This means that the energy cost to the tree to maintain itself is beginning to exceed the energy input the tree receives from photosynthesis. This will lead to the tree becoming less able to resist the spread of decay in the future.
I utilized a tool called an IML Resistograph to test for the presence of decay in four locations around the circumference of the trunk at a height of approximately 4.5 feet. The Resistograph uses a small drill bit to penetrate the tree stem and determine the amount of sound versus decayed wood present in a tree. The amount of sound wood is compared to stem diameter to estimate the amount of strength the tree has lost as a result of the presence of decay. The Resistograph showed very little sound wood present where I tested.
The table below shows an accepted manner within arboriculture for evaluating tree risk qualitatively. The likelihood of tree failure and impact are compared to the potential consequences of failure to determine overall tree risk.
Tree risk assessment matrix. Source: www.isa-arbor.com
If the honeylocust were to fail, the main potential targets would include the entry drive, power lines and the parking lot. This accounts for the failure of the entire tree or portions of the tree, such as individual branches. Potential damage would include property damage and injury to persons under the tree. The most likely failure route is to the east or north, which means damage would occur to power lines and potentially the entry drive. Therefore, I rate the potential consequences of tree failure as SIGNIFICANT.
I rated the tree as LIKELY to fail and impact a target, given the tree's overall condition, combined with its presence near several targets as described above.
As can be seen in the table, a combination of LIKELY failure and impact and SIGNIFICANT consequence of failure equates to a HIGH overall tree risk.
I recommended the tree be removed. There are no remedial actions other than removal that would reasonably reduce the amount of decay present in the tree, which is the main concern. Therefore, the high risk present in the tree cannot be reasonably reduced without removal.
People often ask me what the difference is between a consulting arborist and an arborist/sales rep from a tree care firm. Why am I a consultant and somebody from XYZ tree company is not? While there are many similarities (we are both arborists), there are a few differences.
As a consulting arborist, when I visit a property I am not there to sell the client something. What I am selling has already been sold - generally my time and my opinion. The time involved in visiting a property, writing a report, developing a plan, testifying as a witness, etc. are what a you pay a consultant for. In paying for their time, you are also paying a consultant for their expert opinion on a given topic related to trees. A final product such as a report or tree management plan is also generally provided.
Arborists from most tree care firms will generally visit a property free of charge, provide an evaluation and then prescribe a service, if necessary. They provide this service for free because they make money off of the services they sell during their visits. There is nothing wrong with this model; it is just different from what a consultant will do.
Many consulting arborists also have expertise outside of traditional arboriculture. My main outside expertise is in urban planning, municipal government and data visualization/mapping. Such outside experience gives a consultant a more-wide ranging of trees. For instance, my experience in municipal government is useful in interpreting codes and ordinances as they relate to trees. My knowledge of urban planning is useful in understanding the design and functionality of cities, and how trees can be used as a functional element of this design. Consulting arborists also attain credentials that most others do not, such as Registered Consulting Arborist. Some may have other certifications and accreditations, such as LEED AP, CNU-A or AICP. This just goes to show that they have enough experience in an area to have attained certification.
So when do you need a consulting arborist? And who should hire one?
The ASCA website does a great job of explaining this:
So just be aware of the differences. If what you need is advice, unaffected by a future sale, hire a consulting arborist.
Tree Selection for Homeowners
One of the most common questions I get from clients and attendees at speaking engagements is this:
What tree should I plant in my yard?
I always wish I could give a straightforward answer and instantly spit out the names of one or two trees that will thrive in their yards for the next 50+ years.
Unfortunately it is not that easy, as there are many factors to consider. Failure to think through your choice could doom your newly planted tree, or at least limit it in living up to its full potential. Here are a few considerations to help determine what will best meet your needs and the growing requirements of the tree.
So many aspects of tree health are determined by the soil in which it grows. It is much easier to select a tree suited to the soil you have than to try to adjust the soil to a certain species. Is it clay? Sand? Loam? Cement? Bricks? This website gives a good overview of how to determine the texture of your soil. However, you may want to consider sending in a sample to a local lab if you want a detailed analysis.
(Not so) high quality soil is often what urban trees are forced to grow in.
2. Tree goals
Do you want shade? Wildlife attraction? Fruit to eat? Home energy savings?
A good question to ask is: what is missing in my yard that could be at least be partially provided by a mature tree? For a good overview of urban tree benefits, check out the website for the Friends of the Urban Forest, here.
3. Growing space
What is important here is the mature size of the tree. Make sure you consider the tree's crown as well as its base. The online tree selectors, below, all give a good idea of mature tree height and spread.
This tree needs more space than it has been given to grow, and will therefore never live up to its full potential.
And remember to look up. You don't want to plant a tall-growing tree under utility lines.
Some trees will require more water than others. Some have leaves that can be a pain in the fall. Roots of some species are more prone to lift sidewalks or enter basement walls. Do you want to grow grass/shrubs/perennials under the tree but future shade will require heavy pruning?
These are just a few factors that can cause maintenance issues years down the line. Make sure you take these and others into consideration.
Online tree selectors
Once you have determined the above information, you can input everything into an online tree selector. A couple of my favorites are below.
When selecting a tree to plant, there are a lot of variables to consider - mature height/spread, soil needs, climate, fruiting, aesthetics, etc. Luckily there are a number of online tree selectors that can do the thinking for you. You simply put in the variables (or as many as you know) and the selector spits out a list of trees suitable for your planting location. Below are 5 of my favorites. These work well for the Upper Midwest, but can be applied to many other parts of the country as well. The University of Florida Selector is my favorite of the bunch, but all will work relatively well.
1. University of Florida - http://lyra.ifas.ufl.edu/NorthernTrees/NorthernTreeSelector.swf
2. Minnesota Department of Transportation - http://dotapp7.dot.state.mn.us/plant/faces/index.jsp
3. Arbor Day Foundation - http://arborday.org/shopping/trees/treewizard/intro.cfm
4. University of Illinois Extension - http://extension.illinois.edu/treeselector/
5. Morton Arboretum - http://www.mortonarb.org/trees-plants/tree-and-plant-advice/tree-selector
SITES and the Urban Forest
This past summer, the Green Building Certification Institute (GBCI) officially launched the Sustainable SItes Initiative (SITES) rating system. GBCI is the organization that certifies LEED projects and accredits LEED professionals. SITES addresses many of the landscape and site issues that are vital to sustainability outside of the physical building.
From the SITES website - "The Sustainable Sites Initiative is a program based on the understanding that land is a crucial component of the built environment and can be planned, designed, developed and maintained to protect and enhance the benefits we derive from healthy functioning landscapes."
We've been hearing about SITES for a few years now. It's development began in 2006, through a collaboration between the Lady Bird Johnson Wildflower Center, United States Botanic Garden and the American Society of Landscape Architects. A 2 year pilot recently certified 46 projects across the country.
Being an arborist and urban forester, I am largely interested in how SITES concerns trees. Broadly, the topics of climate change, biodiversity and resource depletion concern urban trees. Specific credits concern the topics of landscape water use, managing precipitation on site, native plants, urban heat islands and energy use around buildings. These are all marked improvements from any LEED rating system, which only gives minimal attention to the landscape. How effective these credits are at achieving their intended goals will be seen as more SITES projects are registered, but I am hopeful that they will make projects both more environmentally sustainable and marketable.
I look forward to having the opportunity to learn more about SITES and hopefully work on some projects under the new rating system.
When selecting trees for landscapes, people all too often stick with the familiar. On the surface, this makes sense. We know what we are getting when we plant a familiar tree. We've likely seen it growing somewhere else. There is likely something attractive or otherwise beneficial about it. Common trees may also be cheaper to purchase.
However, sticking with the familiar causes problems. Too much reliance on a single species/genus can have devastating effects if a pest/disease/condition severely affects the overplanted type of tree (see emerald ash borer, Dutch elm disease). Diversifying our plant profile can help buffer from these effects. Planting more species in a given area can also increase overall benefit of our urban forest, as different species provide different benefits.
Fortunately there are a number of underutilized trees that can do well in and around Chicago. Here are five such trees:
1. Kentucky Coffeetree (Gymnocladus dioicus)
Growth Rate: Slow to Medium
Mature Shape: Oval
Height: 60 to 75 feet
Width: 40 to 50 feet
Site Requirements: Prefers full sun and can tolerate a wide range of soils
2. American hornbeam (Carpinus caroliniana)
Height: 20 to 30 feet
Spread: 20 to 30 feet
Crown uniformity: symmetrical
Crown shape: oval
Crown density: dense
Growth rate: slow
Uses: sidewalk cutout (tree pit); deck or patio; specimen; street without sidewalk; screen; hedge; tree lawn 3–4 feet wide; tree lawn 4–6 feet wide; tree lawn > 6 ft. wide; Bonsai; shade
Pests - Relatively few insects attack hornbeam. Diseases - None are normally very serious.
3. Katsura tree (Cercidiphyllum japonicum)
Uses: shade; street without sidewalk; specimen; parking lot island 100–200 sq ft; parking lot island > 200 sq ft; tree lawn 4–6 feet wide; tree lawn > 6 ft wide; highway median
Height: 40 to 60 feet
Spread: 35 to 60 feet
Crown uniformity: symmetrical
Crown shape: oval, upright/erect, pyramidal, spreading
Growth rate: fast
4. Nannyberry (Viburnum lentago)
Uses: Nannyberry is a shade-tolerant, understory species useful in landscape plantings as shrub borders, taller barriers, hedges, and windbreaks.
General: Nannyberry is a native, deciduous, multi-stemmed shrub or small tree that may reach 36 ft. in height.
Nannyberry is leggy and somewhat open at maturity with an irregular to rounded crown. Suckers often form at the base. The bark is dark gray to black in a pattern of small blocks.
5. Ohio buckeye (Aesculus glabra)
Uses: recommended for buffer strips around parking lots or for median strip plantings in the highway; shade tree
Height: 50 to 70 feet Spread: 40 to 50 feet Crown shape: round Crown density: dense
Growth rate: medium
6. Japanese tree lilac (Syringa reticulata)
Characteristics: medium-sized ornamental tree or very large ornamental shrub -maturing at about 25' tall x 20' wide, although larger under optimum conditions -upright oval growth habit, becoming more rounded with age -medium growth rate.
Site: full sun to partial sun -best performance occurs in full sun in a moist, well-drained soil of average fertility, but it is highly adaptable to poor soils, compacted soils, various soil pHs, and drought.
7. American yellowwood (Cladastris kentukea)
Height: 30 to 50 feet
Spread: 40 to 50 feet
Uses: recommended for buffer strips around parking lots or for median strip plantings in the highway; shade tree; specimen; residential street tree
Pest resistance: no pests are normally seen on the tree
What are your favorite undervalued trees?
A tree inventory is a management tool used to collect attributes of a population of trees in a specific location. Data is collected to accomplish a goal, such as determining maintenance needs, risk assessment, education, etc. These days, inventories are typically collected utilizing GPS/GIS and can be easily accessed and shared on the web. Homeowners associations should be interested in conduction tree inventories for many reasons, including the following:
Knowing the maintenance needs of the trees in your association can help plan for work to be done over several years. For example, a plan to prune the trees in the association would be difficult to create if the pruning needs of every tree are not known. Knowing pruning needs helps prioritize which trees to prune first, and at what cost, so that an HOA can budget for maintenance accordingly.
Informing residents of the types of trees and associated benefits throughout an Association can help improve appreciation for the natural environment. After all, one will likely find it hard to care about a resource they don't even know exists. An HOA can make their tree inventory available to residents so they can see the benefits and needs of individual trees. Residents can access some types of inventories from mobile devices so they can learn about individual trees as they walk their neighborhood.
Environmentally aware individuals may be attracted to an HOA if they see that management cares for natural assets such as trees. Caring for trees can also help lead to certification through programs such as LEED and SITES. These are third party verification services that have been shown to improve sale and rental prices for residential and commercial properties. Content produced as part of an inventory can often be utilized by an HOA in marketing materials.
4. Risk Assessment
While trees provide many benefits, they can also present safety hazards if in poor condition. An inventory will identify hazards and prioritize removal or other mitigation options to reduce the potential for tree or limb failure. Failure to assess and remove tree risks can open up an HOA or property owner to legal action if a tree failure leads to property damage or personal injury.
5. Insurance/Value Appraisal
If a tree is illegally removed through negligence, accident or weather the HOA can often attempt to recoup the value of the lost tree through insurance or legal means. However, appraised value is difficult to determine after a tree has been removed unless tree accurate details have been kept. That is why is important to know at least the size, species and condition of every tree of value on a property. All of this data can easily be collected in an inventory.
Trees as Part of Home Inspection
A home inspection is a crucial part of the home-buying process. White the building itself is almost always thoroughly inspected before purchase, it is also important to inspect the landscape. Trees, as the biggest natural part of a landscape, should be a regular part of a home inspection.
Why Include Trees in a Home Inspection?
Because trees have value. Not only do trees improve the aesthetics of a property, they can also increase property value. Studies claim that property values can be increased by up to 30% for treed versus non-treed landscapes. Trees also provide wildlife habitat, clean the air, help mitigate flooding and remove air pollutants, among many other benefits.
If you wait until after purchasing a home to assess the trees, you could be surprised to later find out that thousands of dollars in maintenance is needed to correct health and safety issues.
If you’re planning on doing construction, your arborist can advise you on the suitability of preserving specific trees for construction. A detailed tree preservation plan can be prepared for trees chosen to remain. This page by Gary Johnson gives a good overview of tree preservation for homeowners.
What about the Trees is Evaluated?
Health – Trees may have safety issues, nutrient deficiencies, water problems or may simply be in a poor location to grow well. By evaluating tree health, remedies can be prescribed to correct issues before they become critical.
Species – Different species have different management needs. Species also vary in what they contribute to a property.
Contribution to Property – Does the tree provide shade? Fruit? Wildlife value? Aesthetics? Is it a good fit for the property, or will it outgrow its space? Questions such as these can determine what your trees bring to your property individually and as a collection
Maintenance Needs – Trees may need pruning, soil management or pest management for health, safety or aesthetic reasons.
Appraised Value – Trees are often appraised for their value in case of loss. If a tree is killed by lightning or illegally removed by a neighbor, for example, you can potentially recover the lost value of the tree. Feel free to read more about appraised tree values here.
Who Performs the Inspection?
An arborist who is an ISA Certified Arborist and/or Registered Consulting Arborist should perform the inspection. You can read more about those qualifications at the links provided. The International Society of Arboriculture provides great info on why you should have an arborist with credentials inspect your trees here.