If you have not read my blog on Selecting a Tree to Plant, I encourage you to do so as it has information you need to know prior to heading to the nursery to make your purchase. Supposing you have those details in hand, have determined a likely candidate for planting and are now at the nursery. What next? Well, if they have a coffee shop, you may want to sit down…this is going to take a while.
You want to purchase a specimen that has a good chance for survival. Yes, I realize that is another obvious statement. And our prior discussion in selection criteria was supposed to give us the input we needed. However, now I am referring to the actual physical qualities of the individual tree you are considering. The key is to recognize “quality”, which may or may not be obvious. Some clues to help you out are detailed below.
No dead stuff, no disease, no bugs, no dry roots!
If you are seeing dead and broken branches or limbs, signs of disease or bug infestation, pass. There are too many better options. You can tell if a twig or limb is dead if it snaps readily with no green showing in the cambium. An incidental broken twig is not necessarily an issue. If the tree looked like it fell off the truck in transit….pass.
Check out the trunk for injuries. You don’t want to see scuffs, bark missing or indentations that might indicate an injury in the past, such as sunscald.
If you see discoloration on the leaves, such as crisp, brown edges while the rest of the leaf is green this may be a disease, it could be drought stress, it could be a number of things. It may, or may not, be serious. Ask.
If you see bugs on the tree but have no idea what they are…ask. There are beneficial bugs and insects that are great to see. And there are some you don’t want to take home with you.
Before we go any further, let me explain that you generally have three different options of types of trees to buy: bareroot, balled and burlapped (BnB) or container. These are not necessarily offered at all nurseries nor are they all offered for all species. But here is a brief explanation of the three.
These are exactly what they sound like. The roots do not have any dirt surrounding them. They are generally only available in the early spring, at least in my area (reminder I am in Montana). They tend to be smaller in caliper size (trunk diameter), 1 inch or less. Don’t let their small stature discourage you from considering them. It may be enticing to look at the big trees, but restrain your impulse for instant gratification. A smaller specimen will establish faster and easier than a larger one with a better chance of survival. The general guideline is it takes 1 year per inch of caliper for a tree to establish. During that time, the vast amount of their energy should be going into reproducing the roots lost in the digging or planting process. With bareroot trees, very little of the root system has been lost, and the small diameter ensures the establishment time is minimal. Then they are off and running!
Some nurseries don’t carry the variety of bareroot as they do for the other options; call ahead and find out who has what. You have a short time period between when they are delivered to the nursery and when they have to be potted up if they don’t sell quickly, so if you do want to consider a bareroot option, do your research before you head out.When the nursery gets them, they heal them in a medium to keep the roots moist ready for the consumer to purchase. Once you make your selection, a common scenario is the nursery will have a tank of water and shredded paper, sawdust, or other medium to put in a plastic bag to keep the roots moist on your way home. Buy it and take it home. Immediately. Don’t go shopping anywhere else. If you are not going to plant it immediately upon getting home, get it into a tank of water and/or keep the roots moist by rewetting whatever media was used, perhaps even adding more. The tree can soak in a bucket of water overnight. But then get it in the ground. That is critical.
The pros are they are cheaper to purchase, easier to handle and have a much larger root to shoot ratio (which is a good thing).
Balled and Burlapped (BnB)
These are trees of varying sizes that have been field dug with their root system wrapped in burlap and then tied into a ball shape, often with a wire cage to hold things together.
BnB trees tend to be bigger, from 1.5 inches on up. Pay attention to the ratio of root ball to trunk (addressed below). These trees lose a tremendous amount of their roots when dug and balled.
They can come in large sizes, which may be enticing. But remember the caveat about establishment and then also consider how heavy they are. All that soil weighs a ton. You may very likely opt to have these trees delivered and professionally planted.
These are trees also of varying sizes that may have been bareroot trees that didn’t sell and were then potted, or they might have been raised in a container from the get go and potted up as they outgrew the initial container. The container may be plastic, a fibrous material (biodegradable) or fabric.
Possibly the biggest problem with container trees is the potential for circling roots. These are when the roots start circling as they hit the restrictions of the container walls. The problem is they don’t stop circling just because you planted them in the open soil. As the tree grows, they can strangle or “girdle” the trunk.
If you are considering a container tree, ask how long it has been in the container. If it is a small tree, it may have just been potted up from being a bareroot that didn’t sell early in the season. In which case, it will have recently lost a great deal of its roots and be at a very vulnerable stage. If you buy it, you may actually want to let it stay in the container for a while to let it regrow some roots then plant it out in the fall.
If it is a larger tree and has been in the container for more than 2 years, be cautious. I would say the chance of circling roots is pretty good at that point.
Now back to our inspection tour…
You want to select a specimen with good structure. Honestly, that is an entire blog by itself and this one is long enough. I will address what “good structure” means in trees in another post.
If you opt for a bareroot specimen, your selection criteria is pretty straight forward. You will look for no damage as listed above. Since bareroot trees are generally healed in sawdust or a like media, you will be able to see the amount and type of root system to judge health and quantity as you lift your selection out of the mound. If there is something amiss in the root system, such as lack of volume or a significant amount of circling roots, you can replace it (or have an attendant replace it) and keep looking.
For container and BnB trees, reach down and feel the dirt in the container or root ball by poking your fingers down a few inches. Dry roots generally mean dead roots. It does not take long for small diameter roots to dry out and when they do, they start dying. I am sure we have all experienced the container plant we let dry out, watered it and it came back. That’s all good and well (well, actually it’s not a good practice), but when we are looking to purchase a tree to plant, we don’t want something that has already been subjected to drought stress which can have a long lasting detrimental effect. If the tree in question is a balled and burlapped specimen that has been allowed to dry out, heads up. Definitely pass on that one. It can take forever to rewet that root ball and since it took a long time for it to dry out, it is dollars to donuts that tree has suffered significant damage.
The plant should be in the center of the container or root ball.
You want to see an equal amount of the root ball around the stem of the tree. The tree shouldn’t be offset, i.e., closer to one side than another. Figure 1 shows an example. The front tree on the right appears to be situated in the middle of the container while the front tree on the left is offset. There are actually a few issues going on with the tree on the left, so a much better choice would be the front tree on the right.
Root ball appropriate for the tree size
With trees grown in container or balled and burlapped, you want to be sure there are enough roots for it to grow. A general guideline for BnB trees is the diameter of the root ball should be 1 ft for every 1 inch of trunk caliper (diameter) measured approximately 6” above the soil line for trees under 4.5 inches; measured at 12” above the soil line for trees over 4.5 inches in diameter. Again, using Figure 1 as an example, the front tree on the right would be a better choice than the tree on the left in the black container (right behind front tree on the left). The tree on the left behind the front left tree has a larger trunk and a smaller diameter pot.
Depth of root ball
If the root ball diameter is less than 20 inches, its depth should not be less than 65% of the diameter of the ball. If the root ball diameter is over 20 inches, it should not be less than 60% of the diameter of the ball.
Example: If you are looking at a tree with a 1.5” caliper (trunk diameter 6” above the soil line), its root ball should be at least 18 inches in diameter and 12” deep.
Here’s the rub: where exactly is “the soil line”. The soil line is intended to be at the root flare, which is the depth trees should be planted. (Coming soon: Planting a Tree Properly) The top of the soil you see in the container or the top of the burlap may be above that desired spot. In fact, in our experience, many (if not most) cases, the soil is above the appropriate “line”.
The line we start measuring from is at the root flare, which in many cases has been buried during the digging process of balling and burlapping or after many container transplants. You need to find the root flare. This is going to be easier to do with a container tree than a balled and burlapped tree. Feel free to ask a nursery associate to help you.
Now, how do you know what the root flare looks like? Many people confuse the graft (a LOT of trees are grafted) with the root flare. But keep going, you want to see roots that are at least the size of a finger going out and away from the trunk on all sides. Little, tiny roots don’t count. Those may be adventitious roots which grew in response to the tree being buried too deep. And is what will happen at home if you plant it at that depth. Once you find the true root flare, measure from there to the bottom of the ball to determine if there is sufficient depth of root material.
For container trees the criteria on size varies a bit. If you have a 1/2 inch caliper tree that is 4 to 6 ft tall, the minimum root ball diameter should be 12 inches, with a minimum depth of 7 7/8 inches. For every 1/8 inch caliper increase and 2 ft more in height, the minimum root ball diameter goes up an inch and the minimum root ball depth increases by ½ inch. These are definitely broad guidelines, but it gets you in the ballpark.
If you want to get really specific, the American Standard for Nursery Stock, ANSI Z60.1-2014 is available on line for free at the American Horticultural Society website.
Overwhelmed yet? I know. It is a lot to take in. But the more informed you are, the better selection you will make.
Spring is just around the corner and you are determined to plant a new tree. How do you make a good decision? What IS a good decision? We are often asked for suggestions on species to plant. It is never a quick or easy answer. Please note: Although I am referencing trees here, this information is applicable to pretty much any perennial plant.
There are many factors to consider prior to hitting your favorite nursery. By the way, “your favorite nursery” will be the one that has the tree species you want, of high quality, at a price you are willing to spend.
Pull up a comfortable chair, pour yourself a cup of tea … this may take a while.
Final species selection is determined by various criteria involving site characteristics, your environment and climate as well as your own personal preferences and tolerance levels. Buying that popular tree everyone has been talking about may, or may not, be a suitable choice for your property.
Before you decide what you are going to purchase you need to go through a check list which will limit what you can plant and expect it to survive. There is nothing more frustrating than to plant a tree, have it do well for a little while and then decline and die. Trees take a long time to grow and mature; you want to do everything you can to ensure circumstances are going to make that possible.
Where are you going to plant it?
You need to determine where you are going to plant the tree. No, “in my yard” isn’t a sufficient answer.
Site characteristics affecting your choice include space for it to grow to its full potential. Ok, that sounds so obvious it wasn’t even worth mentioning, right? I cannot tell you how many people call us to prune a tree that has “outgrown” its spot because the people had “no idea how big it would get”.
First of all, this is not the tree’s fault and second, size information is readily available from the internet, local nurseries and arboreta. Take the information seriously. If reliable sources say a tree has the capability of getting 30 to 40 feet tall and you have no perception of what that actually means, consider a two-story house with a peaked roof is approximately 25 ft in height. If that height potential makes you uncomfortable, select a tree which will max out smaller. Thinking you can “keep a tree small” by pruning is setting yourself up for a high maintenance situation which translates to high expense and is unnecessarily stressing the tree through repeated wounding.
It is not a bad idea to take a drive around town or your neighborhood to see who has what planted. But a cautionary note about getting information from homeowners. My sincere apologies and I don’t mean to offend anyone, however, homeowners, unless they are arborists and, unfortunately even then, are not necessarily reliable resources as to what species will do well in your area. Too often they fail to take into consideration extenuating circumstances such as soil characteristics and properties, planting practices or the quality of the specimen purchased which may all limit survivability or growth.
Back to your criteria. In addition to your comfort level on height, the tree requires the sky above it be clear of conflicts. Do you have overhead utilities? Look up! Do not plant a tall tree under utility lines whether they are house lines or main lines. This will also cause it to become a high maintenance nightmare with the very real probability of your tree being disfigured to accommodate those lines. Even if pruned away from the lines, it remains a hazard to those lines during storms, possibly disrupting your service in the case of house lines and affecting your neighborhood in the case of main lines.
Utility companies generally will not prune trees under house access lines; that is the consumer’s responsibility. They will typically prune trees under major access lines. Some people have the impression this is a free service, when in fact it costs all of us money in higher utility rates. Be responsible and do not plant anything growing over 15 ft under any main utility line. I know recommendations allow up to 20 ft, but trees outgrow their potential all the time. Play it safe. Plant a shrub if you absolutely must have growth in that area.
In addition to height potential, consider how wide will the crown get. Look at those plant specifications again. Again, take it seriously. If the spot you are considering is fairly narrow, there are cultivars specifically created to grow upright rather than spreading. These may say “columnar” or “fastigiate” in their descriptions. These are excellent choices if you have limited space.
In addition to basic height and width of the tree, consider how big the trunk itself will get. Some trees may grow tall without putting on a great deal of girth and some can get massive.
A Lombardi poplar matured too close to a house.
You also need to consider the available soil space. Tree roots need room to grow just as much as the above ground structure of the tree. Do you have enough soil volume to support the root system of the tree you are considering? Some people think roots stop at the drip line, but that isn’t the case. Tree roots can grow much further than the drip line.
While you are looking into general characteristics of your potential tree, pay attention to what is said about the root system. Not only is available space necessary, but the root structure may have attributes you find less than pleasing in your yard. Some trees have strong lateral root systems staying very close to the surface. Some are oblique or heart shape, growing out and then down. Some species maintain their tap root through maturity, although the majority of species do not. Then there are many systems that are a combination.
Are there underground utilities you need to be aware of? CALL BEFORE YOU DIG! This is a requirement in many states and is not limited to professional companies. You want those lines to be significantly far away from the mature size of the trunk.
If you have a septic system and drain field, do not plant the tree on top of either the drain field or the tank. Tree roots will not create a crack but they can and will take advantage of one that appears.
When selecting a suitable tree to plant you need to consider as many aspects of the climate as you can. The United States Department of Agriculture (USDA) Hardiness Zone Maps are based on winter lows which tells you the probability of the plant surviving the winter.
The U.S. Sunset Climate Zones consider many other factors as well, including length of growing season, timing and amount of rainfall, winter lows, summer highs, wind, and humidity.
The American Horticultural Society has developed heat zone maps as well.
These all provide helpful information to incorporate with your onsite observations of your specific location. Are you mostly in deep shade because of large trees around you? Is your property exposed to substantial prevailing winds? Are you in a cold sink? Do you have an enclosed yard with a solid fence? How tall is the fence? The more detail you note about your site, the better choices you will make.
Soil matters – a lot
The type of soil and its characteristics may be the ultimate decider in whether your tree thrives, struggles or dies. These characteristics include pH, texture, infiltration and drainage of water. You also need to be aware of limiting factors such as compaction, salinity. Future blogs will be dealing with the importance of and how to maintain healthy soil.
You take all this information and compare it to the needs of the tree you are considering to determine if it is a “good fit”.
A lovely Autumn Blaze maple planted with ample room in a site with appropriate conditions.
What is its purpose?
Generally, when we plant a tree it is with a specific function in mind. Do you want future shade for a patio, the house, a specific room in the house? Do you NOT want shade to inhibit growth in your vegetable garden?
Maybe it’s purpose is to supply you with fresh fruit. Or to provide a focal point which will enhance the aesthetics on your property by providing colorful foliage or flowers or because you are intrigued by its unusual growth habit.
A weeping juniper adding year-round interest with striking growth habit.
You are narrowing down your choices. Do yourself a favor and be prepared with a few candidates. Your nursery may, or may not, have your first choice. If you are determined on a specific species, plan ahead and order it. Check with your nursery to determine their ordering schedule. Some place orders months in advance. Others may have stock coming in regularly.
Please see my blog on “Selecting a Quality Specimen to Plant” for further information before you buy.
First off, some of you might be asking “what is a tree island?” Picture a tropical island surrounded with water, there is your island. Now place that island in your landscape surrounded by turf grass, plant a tree in it and, voila, you have a “tree island”. In landscape design, you might create the opposite effect, having the turf grass as an island surrounded by tree berms and other designated areas. Since our focus is on trees (that’s what arborists tend to do), we pretty much call anything that has separated trees from turf “tree islands”.
There are multiple purposes involved, but the two most common are:
1. Creativity in design – a way to make your landscape more interesting. (Personally, there is nothing more boring than seemingly endless acres of lawn with a lonely tree popping out here and there).
2. Separation of diverse plant species requiring different cultural practices, allowing more efficient management of each landscape component.
There is no doubt a tree island can set off a specimen plant(s) to advantage: drawing attention to unique structure, colorful foliage, showy blooms. The tree island may also be planted in a variety of compatible species for maximum effect and improvement of soil health. (A topic for another blog.) But an important feature is the ability to provide a buffer zone from management practices that are harmful to those plants within the island.
Tree islands also may provide diversity through compatible plant varieties.
Lawn care management practices can literally be deadly on trees. Weedwacking, the use of mechanical tools to mow grass and weeds away from the trunks, is more harmful than most people realize. They cannot conceive a little string can cause significant injury to a massive tree. Well, they can and do. And they can kill a young, thin-barked tree in an amazingly short period of time.
Damage is seen at the base of the tree where the bark is missing.
Lawn mowers also inflict damage. The repeated running into the tree causes permanent injuries. We were called out to remove an ash tree which was over 50 percent dead. The homeowners asked what we thought was killing the tree. One of the first things we do is look at the base of the trunk. Investigation revealed a significant injury encompassing almost 50% of the circumference of the tree. After we had made the final cut, I counted tree rings to see when the damage had begun. I told the homeowners the damage started approximately 11 years prior. The husband admitted that was about when he got his riding lawn mower and the flange of the mower hit the tree on that side almost every time he mowed.
Damage from flange on riding lawn mower.
Basal cut showing results of repetitive damage.
We have a tendency to think trees can withstand anything we do to them because we generally don’t see immediate consequences of our actions.
Other lawn care management practices which can harm trees and other plants are commonly used chemicals. Many products have “weed and feed” components. In addition to fertilizer an herbicide is included to deal with broadleaf weeds, such as dandelions. Trees are broadleaf species and some species are very sensitive to those chemicals. Tree islands at least back the herbicides off from the critical root zone. We recommend hand pulling or spot treatment of broadleaf weeds that cannot be tolerated rather than wholesale broadcasting of herbicides.
A short note on the roots of trees. They do not stop at the drip line. Many people feel you can do or apply anything if you stay outside the drip line. Well, the roots are out there. In fact, they can grow much further away from the trunk than the tree is tall. Tree roots grow wherever they can. They need space, oxygen and water. Some grow close to the surface, some can go much deeper. Many roots do congregate at the surface as that is where the most space, oxygen and water are and so are able to take up anything applied to the soil.
When designing a tree island, a common practice is to lay down weed fabric prior to applying some form of top dressing. This is not recommended when the top dressing is of an organic nature, such as wood chips, compost, or bark, which is what we recommend. Landscape fabric will block the biological exchange between the organic mulch and the mineral soil below. This means none of the benefits mulch can provide the soil will be available. This caution goes whether the fabric is pervious (allowing water and air to penetrate) or impervious (blocking water and air).
If you are using some kind of non-organic top dressing, such as rock, then it becomes less of an issue. I have personal prejudices against some of the non-organic products, but these will be dealt with in a future blog specific to top dressings.
This may seem an odd topic for an arborist and blatant lover of trees. But when dealing with innumerable clients over the years as well as speaking to groups (who are not directly clients), you have to stay realistic. Some people are just simply not as enthralled with trees as we (arborists and lovers of trees) would like to think or take for granted.
The biggest issue we hear: “They’re so messy!” Well, I can’t really argue that but it is tempting to ask if they have any children and if there is any maintenance involved with cleanup. Since I am trying to keep avenues of discourse open, I bite my tongue there.
Yes, trees produce debris. That actually is a good thing. And important, even mandatory, in a healthy environment. (I will go into this a lot more in my blog(s) on soil organic matter and healthy soil – yet to come.) In a natural setting that debris is integral to supplying nutrients back to the soil and soil organisms and hence the trees themselves via the complex breakdown of the organic matter (what we are calling “debris”). We tend to want our areas a bit too tidy.
The complaints escalate come autumn when those glorious leaves that have been giving us wonderfully-appreciated shade all summer, and which we love to oooh and aaah over in their fabulous color displays, start to fall. And keep falling. In fact, they seem to multiply on their way down to the ground. A fact that has yet to be scientifically proven but anecdotal evidence suggests….
At that point, faced with a yard full of 2-foot-deep leaves, FAR more than you can mulch and use in your garden or flower beds, to say nothing of the whining of the designated rakee in the family, you are seriously contemplating cutting all offenders down. If you live in town, this problem is compounded by the fact that leaves have no respect for property lines. They not only fall over the fence from your neighbor’s trees but they BLOW IN from who knows where! If a tree identification was to be taken from your property by the leaves on site, you would assume you lived in an arboretum, an impressive one at that! Where in reality you may have one, maybe two, species actually situated on your place.
But you take comfort in the fact you will get them all raked up and that will be that for the season. Ok, except for the next wind that blows all those errant leaves from, apparently, the next state, ….and the fun resumes. Encouraging words like “it provides good exercise”, or “it’s called job security” (my personal favorite which so far, no one appreciates), or “it’s a wonderful family activity” (unless you have a dog and then they spend as much time scattering the piles as you do raking them; however, the dog is getting good exercise and a sense of bonding with the family, so there’s that) are little solace at this time.
And what on Earth do you do with all those sacks of leaves???? Well, many cities have places to dump them. In some areas they will magically disappear if left bagged on the curb. They actually are tremendously good for gardens, both vegetable and flower, as well as top dressing any other area involving soil.
When you do rake up your leaves, make sure you leave a substantial amount under the tree they fell from. If you don’t have a tree island under your tree…. well, we need to talk. There will be a blog about that coming up as well.
Trees have a genetic growth rate for development based on their species and influenced by their environment. People often base a selection of a tree on growth rate preferring something where they will see rapid results rather than opting to buy a tree perceived as “slow” growing. And many species which have the reputation for being slow growing may actually grow fast in their youth.
Before you succumb to the desire for instant gratification, consider some of the following points because, as is often the case in life, there are trade-offs.
Fast-growing species tend to have weaker wood and can be shorter lived than slow growing species. This relates to their ability or “strategy” in dealing with disease and insect pressures, which is the topic of another blog although briefly addressed in Trees Don’t Heal, They Seal.
A fast-growing tree whose wood is weak can be a higher maintenance tree than slow-growing species. They may require more intensive or ongoing clean up as they have a tendency to be “self-pruning”. A lovely example being a willow tree that will shed limbs or twigs every time the wind blows. They often require pruning on a shorter rotation in order to keep them in check within the landscape. They may quickly outgrow the site, or need pruning simply to maintain a desirable structure.
There is a certain mindset that states a tree can be made to grow faster by fertilizing. Well, that is true. However, pushing vegetative growth (which is what fertilization does) is at the expense of the tree’s ability to put resources into root development, storage and defense; important functions for health and longevity in trees. As I just stated, a fast-growing tree will generally require pruning on a shorter time rotation than a slow-growing one, add in the fact of forcing growth to make it grow faster, and you end up compounding that issue. And that wonderfully succulent growth is candy to many insects as well as disease organisms. Many fast-growing trees already have a long list of insect and disease organisms, increasing that probability by fertilization, and you have a tree with a maintenance schedule and cost factor you may not have counted on.
Bottom line: faster is not always better. When it comes to trees you often want to bank on the tortoise, not the hare.
For the most part, trees are able to take care of themselves pretty well. However, since we take them out of their native environments and plant them where they may, or may not, have grown by themselves, there are a couple of things we can do to help them out on a seasonal basis.
If you live in an area that actually gets winter, you know, cold temperatures, snow…that kind of thing, you need to consider protecting your trees’ trunks.
The candidates most likely to need this are young, newly transplanted trees. Why? Because their bark is thin. Thin-barked trees are particularly susceptible to sunscald which is an environmentally caused, abiotic, injury which can be seriously damaging. The problem is created in the winter when the sun is lower in the sky and typically occurs on the south and southwest sides of trees. The sun heats up the bark, the sap in the cambium flows, the sun goes behind a cloud or sets creating a sudden drop in temperature which can cause lethal freezing. The damaged tissue is now susceptible to pathogenic organisms as well as having sustained the initial physical injury. The damage is seldom seen for months if not years as the dead and dying bark does not slough off the tree immediately. When finally noticed, this is seen as a “sudden” event by the homeowner but the damage actually occurred in the past.
There is no “cure”. (See Blog on Trees Don’t Heal, They Seal) Prevention, though, goes a long way. In late fall, install a protective shield on the south/southwest side of the trunk. It may go all the way around the trunk if using one of the white tubes sold for this purpose. If your tree has grown too big for the tubes (generally sold in 2” and 3” sizes), you can use flat, white corrugated protectors and tie them on.
Whereas this is generally only necessary for young trees until their bark is sufficiently thick enough to withstand normal winters, there are a few trees that remain susceptible their entire lives. Species such as Mountain ash trees, Sorbus spp., and the extremely popular Autumn Blaze maple, Acer freemonii, ‘Autumn Blaze’, are two examples. Protection for trees which stay sensitive to sunscald can be accomplished by planting understory shrubs and perennials on the south/southwest side of the tree which will give it winter protection as well.
© 2017 McNeill’s Tree Service
Trees cannot regenerate tissue over a wound as humans do. They seal off the injury and encapsulate it, hopefully stopping pathogen entry or progression in the process. But the wound is always there and visible on the inside if not also from the outside.
This is why responsible arborists try to take as much care as possible to minimize wounding caused by pruning. Because, technically, all pruning cuts are wounding the tree. But then so is the swing set attached to a limb, the bump from the car, the bicycle leaned against it, the dog tethered around the base, the lawn mower hitting it every time you mow, and don’t even get me started on weed whacker injuries!
Every poster, sign, birdhouse, decoration affixed to a tree is injuring it to one degree or another. Cats mark the trunks with their claws, birds peck holes as they go for larva under the bark or accessing sap exudations, tapping to produce maple syrup, the list simply goes on and on. In fact, I often say, trees live in spite of us, not because of us.
When a tree sustains an injury, an air embolism is created. The tree responds by trying to contain the damage this will cause by initiating chemical responses of various strengths, containing it from progressing up and down the trunk (axially), into the center of the tree (radially) and sideways (laterally). There is a more powerful reaction produced as a barrier which inhibits disease or dysfunction from extending out into new wood formed after the initial injury.
Arborists will know this sequence by the acronym CODIT, Compartmentalization of Decay in Trees, as initially described by Dr. Alex Shigo, with the boundary zones, Walls 1, 2 and 3 and the barrier zone of Wall 4.
Dr. Dirk Dujesfieken has described this process further and CODIT is now being referred to as Compartmentalization of Damage in Trees. Discussion of the CODIT Model and the CODIT Principle are lengthy subjects and topics for future blogs.
© 2017 McNeill’s Tree Service