Chapter 11: Save Existing Trees—They Rarely Need to Be Removed

We have talked a lot about planting new trees, but what about saving existing trees? By saving an existing tree we preserve all the benefits generated by that tree—soil, water, carbon, and outrageous diversity. We also save the money we might have spent on removing it. Was it Benjamin Franklin who said, “a tree saved is a tree earned?”

In my professional career I have observed that trees are often removed based on issues that either do not exist or could be easily solved without removal. These decisions are usually made due to a lack of knowledge about trees and alternative options. In this chapter my goal is to provide the information necessary to make better-informed decisions about whether a tree needs to be removed. We will discuss three main topics:

1. Trees we generally shouldn’t worry about
2. Trees we should potentially worry about
3. How to inspect a tree for potential issues

Before we begin, let me give some disclaimers: trees are highly dynamic, living organisms that vary greatly by species, location, weather conditions, and more. My knowledge of trees is mostly limited to the ecosystems here in the Piedmont of North Carolina. It’s not possible for me to describe or anticipate every condition or event that could possibly lead to health decline, structural failure, or death of a tree. I cannot guarantee that trees will be healthy or safe. Therefore, take all of this chapter with a grain of salt—if in doubt, please hire a trained professional with one or multiple of the following credentials: ISA Certified Arborist, ISA Tree Risk Assessment Qualification (TRAQ), ISA Board Certified Master Arborist, and ASCA Registered Consulting Arborist.

Make sure this professional aligns with the values put forth in this book. For example, find a professional from a company that emphasizes the importance of trees on their website and does not feature or glorify tree removal. Better yet, choose one that does not even offer tree removal services if this option exists. Tree removal projects are expensive and generate a great deal of revenue for most tree service companies. It can be hard for a professional to walk away from a removal opportunity, especially if work is slow or if they need to meet a target (I’m speaking from past experience from when Leaf & Limb used to remove trees).

Trees We Generally Shouldn’t Worry About

After many years of working in the tree service industry, I have heard many unfounded fears and misinformation when it comes to trees and the supposed need to cut them down. Here are the concerns I hear most often and why they are not generally concerning.

“I saw my tree swaying in the wind (or a storm) and I’m worried it’s going to fall on my house!”

Tree movement is a good thing! They are supposed to move. As they move, trees grow stronger by developing something called response growth. Think about how we humans work our bodies to build muscle: we lift things, push things, and move around. Although the physiology is very different, the concept is the same: when trees move in the wind they grow stronger. In addition, trees have all sorts of amazing structural features that allow them to withstand high winds, such as leaves that reconfigure into cones to minimize drag, a high twistiness-to-bendiness ratio in the trunk, and tensile buttressing, to name a few.

In the face of a hurricane, tornado, or major wind event all bets are off, even for the strongest and most healthy trees. But even if we have no trees on our property, that storm system can still drop trees and branches from other sites onto our house or building. I have personally witnessed this on multiple occasions during various storms here in North Carolina. All this to say, there is no reason to remove a tree because of the possibility of extreme weather and most certainly no reason to remove a tree because it sways in the wind.

“The tree is too close to my house. I’m afraid it will fall and cause damage—and maybe kill someone!”

Live trees have springy branches full of leaves that act as sails when they fall. They tend to fall more slowly and land with less impact, creating less damage. Buildings rarely collapse; roofs are strong and are designed to protect those living and working below. In my experience, the most serious damage occurs when live trees puncture the roof and rain enters that hole, creating internal water damage. Dead trees are different—they fall with force. If these are located near a building or house and could cause harm, they should be removed.

For those worried that a tree will fall and kill someone we love, the chances of this happening are extremely low. To put the risk into perspective, a review of mortality data in the United States found that nationwide there were 407 deaths from wind-related tree failure during the 13-year period from 1995 to 2007. At the individual level, that comes out to about a one in 690,000 chance each year. Compare this to your chances of dying in a motor vehicle accident (one in 9,000) and by drowning (one in 76,000). These risks are far greater, yet many of us think little of driving multiple times every day (or relaxing in and around water).

“That tree is HUGE! It scares me so much—it needs to be cut down.”

The huge trees are generally the oldest trees. They have survived many years and weathered many storms. They have developed great strength and resilience in the face of many challenges. These are usually the safest trees we should fear the least. This assumes they have not been damaged or disturbed recently. An example of this would be a construction project nearby that caused damage to the tree’s root system. This warrants closer inspection—more on this soon.

“I need to remove the tree because its roots are cracking my pipes, damaging my foundation, raising my sidewalk, or ruining my parking lot.”

Roots in pipes, foundations, or lifting hardscapes often lead people to remove the offending tree. But this is usually unnecessary, resulting in wasted money and the loss of a healthy tree. Let’s start with pipes and foundations.

Tree roots seek food and water. They have no interest in foundations and pipes. Tree roots are like melted cheese; they ooze through and around objects, looking for the path of least resistance. They have no punching power. When roots encounter pipes and foundations that have no cracks, they turn and grow around or alongside these structures.

But if they encounter pipes and foundations with cracks, they often enter in search of water and other basic needs. These cracks usually occur due to improper installation, age, or settling. When plumbers, inspectors, and other technicians find roots in the pipe or foundation, they usually blame the root because they mistake correlation with causation. This basic mistake in logic has happened so often that trees now have a bad rap for damaging pipes and other infrastructure, though they often play no part whatsoever in the damage. The solution is to prune the root and replace the pipe or fix the foundation, not to remove the tree. This will save us a lot of money on unnecessary tree removal costs.

With sidewalks and hardscapes in general, roots do tend to cause more issues. But there are many solutions that allow us to address the issue and preserve the tree. Here are some ideas:

• We can install root barriers on the outer edge of the hardscape to prevent roots from growing underneath. This is typically a proactive solution we must implement before the roots reach the hardscape.
• If a root is already causing an issue, we can prune the root and use a pavement grinder to sand down the portion of the hardscape that has been lifted. We may also be able to slide a root barrier in place to prevent future intrusions.
• There are companies that use subsurface injections of foam and epoxy to lift and level the hardscape. This can be a cheap, easy way to level a hardscape while leaving the tree and its roots intact.
• For sidewalks specifically, consider pouring an ADA-compliant rubber overlay or equivalent (there are many options) on top of the lifted portion.
• Maybe the hardscape is old and needs to be replaced? Resurface the area taking care not to damage the roots. We can do this by instructing our contractor to use a jackhammer and hand tools only and to avoid using heavy equipment near the roots. This will limit damage to the root system. Resurfacing allows us the opportunity to add more gravel and level the surface while leaving the roots intact.

The list goes on. I recommend exploring these and other options before making the decision to remove the tree. Here is a great resources for those interested in more:

More great options for how to deal with roots and sidewalks

And let’s not forget one last option: do nothing. I realize that at times there may be city or HOA requirements to address the issues. We should also consider the needs of the elderly, pregnant, folks who rely on wheelchairs, and so forth. But if these are not a concern, consider leaving things as-is.

“I want to thin out some trees to increase the health of the largest trees.”

It is normal for trees to grow in dense stands. This is typical in forests. Trees are stronger and healthier in groups than they are as individuals. In groups, their roots interlock and increase their holding power within the soil. They are less likely to blow over. From a safety and health aspect, thinning trees creates issues. It does not solve them. Better to ignore the situation and let the trees sort things out among themselves.

“I need to remove the tree because it is at the end of its lifespan.”

A tree does not reach the end of its lifespan unless it has a fatal health issue or a structural defect that could cause it to fall and create harm to those nearby. Does this tree have such an issue? Could the issue be addressed by improving its structure or health? We will learn how to do these things in Chapters 12 and 14. In the absence of an issue, trees live a very long time. Maples can grow to be 400 years old in the wild. Some pine species here in North Carolina can reach ages of 200 to 500 years. There are oaks in the UK that are over 1,000 years old.

The point of all of these examples is that there is either nothing to worry about or there are better, cheaper solutions available than removing the tree. Now let’s talk about trees we should potentially worry about.

Trees We Should Potentially Worry About

I want to immediately state that if we have one of the situations described next this does not mean we need to remove the tree. It means we should pay extra attention to that tree and consider calling a trained professional for additional advice. This assumes that the tree could harm people or property. If it is in the woods, or in an area where it will not cause harm if it falls, we have nothing to worry about. Leave it for the birds and other life that love dying and dead trees.

New Wind Exposure

When building new neighborhoods, shopping centers, and so forth, developers often clear-cut part of the forest. As a result, trees that were once sheltered in the heart of the forest are now exposed to new wind forces they have never encountered. They have not developed the necessary response growth to withstand these new winds. This makes them susceptible to what is known as windthrow, which is a fancy term for being blown over. It will take many years, perhaps over a decade, for these trees to adapt to their new conditions. If all goes well, they will move in the wind without falling and become stronger as they do so. But until then, they should be inspected every six to 12 months since they are more likely to fall than trees that have experienced consistent wind forces for the duration of their lives.

Construction Near Trees

Any time construction, digging, trenching, or disturbance of any kind (we’ll call these construction for ease of reading) happens underneath the canopy of the tree, there is cause for concern. Construction often leads to smashed and cut roots, a decline in tree health and stability, and damage to the soil ecosystem. To learn more we need to get technical:

The area underneath the canopy near the trunk is particularly important, since there is a high concentration of roots located here. We will call this the critical root zone (CRZ). I define the minimum CRZ as a circle having a radius equal to the diameter of the trunk measured at 54 inches above the ground (this is called diameter at breast height or DBH) × 18, as measured from the outside of the tree trunk. For example, if we have a trunk that is 12 inches DBH, the CRZ is calculated as follows: 12 inches × 18 = 216 inches or 18 feet. Thus, the CRZ is a circle with a radius of 18 feet, as measured from the outside edge of the trunk. I prefer a CRZ equal to the edge of the canopy, if possible, since more healthy roots are better for the tree. But this is not feasible for all construction projects.

There is another important zone, which we will call the structural root zone (SRZ). This is a circle whose radius measures DBH × 6 as measured from the outside edge of the trunk. Using the same example as before, this would be 12 inches × 6 = 72 inches or 6 feet. So the SRZ in this scenario is a circle with a radius of 6 feet as measured from the outside edge of the trunk. Please note that the definition of SRZ may vary by expert. Some go so far as to say that SRZ is equal to DBH × 3, which would be 36 inches in this example. I prefer to err on the conservative side.

The most dangerous disturbance is that which bisects the SRZ. According to best practices in the tree service industry, bisecting the SRZ leads to an increased likelihood that this tree has been structurally destabilized. It’s much like removing a leg (or two) from a table. To be fair, this standard is not always accurate—it can vary based on where the majority of root growth is located and how deep the cut was made.

For construction outside of the SRZ but still within the CRZ, the primary concern is damage to tree health, not necessarily structural stability. The damage can often be remedied through a soil improvement process, especially if it affects less than 25% of the CRZ. For this process, we may need to hire a professional because these are not common tools. Here are specifications for this process:

1. Add 1–2 inches of leaf mold or leaf compost on the affected area or underneath the entire canopy.
2. Use an air knife powered by compressed air to turn this material into the soil.
3. Use the air knife to stir the soil to a depth of 8–12 inches.
4. When everything is done, cover the entire area with 3–6 inches of arborist wood chips.
5. If this occurs during the growing season, drench the root zone in water.

NOTE: If a professional or the tools are not available, proceed with adding the leaf mold/compost and arborist wood chips. These will help.

Once the soil improvement is done, we should continue doing everything possible to rehabilitate the soil within the CRZ of the tree, such as adding compost tea and replenishing arborist wood chips, all of which we will discuss in more detail in Chapter 14. In addition, the tree should be inspected every six to 12 months for no less than five years, but ideally 10.

It is worth noting that even in the absence of specific construction damage, this approach is often very effective at boosting the health of a tree, especially if that tree has not received care in the past. The sub/urban landscape is generally a tough place for a tree to grow!

Lifting Root Plate

Sometimes a leaning tree is growing toward the sun and is perfectly stable. This is usually the case. But sometimes a leaning tree is slowly falling over, which can be dangerous if there are people or structures underneath. We can discern the latter by inspecting the area next to the trunk on the opposite side of the lean. Are we able to see soil and roots lifting? Are there roots bulging out of the ground? Does the soil feel extra spongy under our feet? These are all signs that the tree may be falling. We must make sure we have a clear visual on this area.

I recall one specific example where I thought a leaning tree was stable. The ground on the opposite side of the lean felt firm and I could not see or feel any bulging roots. But English ivy was growing here and obstructing my view. To be extra sure, I removed all the ivy. I was shocked to find three large structural roots bowing out of the ground. I had been unable to feel them through the ivy. I traced these roots directly to the base of the trunk and was able to immediately determine that this tree was in imminent danger of falling. Because there was a house nearby, I advised that this tree needed to be removed (and gave the homeowner a handful of native saplings to replant in place of this tree).

Invasive Pests

There are a variety of invasive insects and diseases that kill trees and are challenging or impossible to stop. Some that come to mind are emerald ash borer, Dutch elm disease, Asian ambrosia beetles, chestnut blight, and beech bark disease. The species will vary considerably by region. Some of them can be deterred through a combination of preventative measures (e.g., trunk injections to impede emerald ash borer) and ensuring the tree is in excellent health. But once an invasive pest infests or infects a tree, the best options are often to either remove the tree or let it rot in place.

Invasive Trees

Invasive trees damage local ecosystems. They should be removed and replaced with native species. Research on mid-Atlantic ecosystems has found that native plants support 35 times more caterpillar biomass (total weight of the caterpillars) and three times more caterpillar species than non-native plants.

How to Inspect a Tree for Potential Issues

Let’s briefly dive into the process for evaluating a tree. I want to emphasize that this next section is not a thorough tutorial. It covers the basics. Most of the things I outline next can be treated or addressed without needing to remove the tree. Before we dive into the details, here is a basic tutorial:

Canopy

Let’s start at the top of the tree and work our way down. If we see upper branches dying, starting from their outer tips, this is a common and obvious sign that the tree is declining in health. This can occur throughout the entire canopy or within a concentrated portion of the canopy. This decline in health is often related to the tree being rooted in dirt, not soil. We can fix this using the soil improvement process outlined earlier in this chapter and the practices in Chapter 14.

It’s important to note that branch death starting from their tips is very different from branches dying in the lower and interior portions of the canopy. Dead branches in the lower and interior canopy are normal and nothing to worry about. They are being shaded out by upper and outer branches.

Here are some other things to look for in the canopy:

• A lack of leaves when there should be leaves.
• Foliage falling before the dormant season begins.
• A deciduous tree holding on to dead leaves when they should have dropped.
• Foliage turning unusual colors at unexpected times.
• Insects defoliating more than 20% of the canopy. Keep in mind that some insect damage is good, normal, and to be expected. After all, insects and herbivores need to feed from trees and other plants.
• A low density of leaves as compared to other trees of the same species.
• Branches that protrude from the edge of the canopy further than other branches. These could be at higher-than-usual risk of splitting. They should be pruned to reduce length (more on this in Chapter 12, where we discuss structural pruning).

Trunk

The next area to examine is the trunk. Here are some possible issues to look for:

• Peeling bark, cracking bark, or other damage along the trunk which is not typical for that species. Ditto for abnormal colors and texture. Ignore lichen and moss. They are totally normal and nothing to worry about.
• Large holes, hollows, and columns of decay. See the sidebar for more information on this topic.
• Ooze, discharge, fine sawdust, or liquid seeping from the trunk.
• The smell of fermentation wafting from a specific location on the trunk.
• A strip of exposed wood running up the length of the trunk, which could be a sign of a recent lightning strike. Trees can often recover from lightning strikes.
• A new lean where there never used to be one. The tree could be slowly tipping over.
• Multiple trunks with a tight V-shape at the point of origin. These types of trunks are more likely to split over the long term and should be addressed through structural pruning if possible.
• A root collar buried under arborist wood chips, mulch, or dirt. We know from the previous chapter that a buried root collar will kill a tree. If we cannot see a prominent flare at the base of the trunk, or if it looks like a telephone pole that disappears straight into the ground, we know the root collar is buried—it must be excavated and exposed ASAP.

Roots

Roots are a very important part of the tree. They make up as much mass as the canopy, meaning that the weight of roots underground is equal to the weight of branches above ground. That said, the structure of the roots is different from the branches. In the sub/urban landscape, roots usually only grow about 2 feet down into the ground (main structural roots sometimes grow to a depth of 3 feet) and they extend beyond the edge of the branches, typically at least three times as far. These roots form a wide, flat plate underneath the tree.

Here are some thing to examine:

• Dirt versus soil. This is one of the most common underlying health issues we see for trees in the sub/urban landscape. It leads to a decline in health, which makes the tree more susceptible to other issues, like pest attacks. An easy way to check for dirt versus soil is with the Screwdriver Test (see the sidebar). We can fix this using the soil improvement process outlined earlier in this chapter and using the practices described in Chapter 14.
• Watch for mushrooms growing at the base of the trunk or on the nearby roots. Most are harmless, but there are a handful that could be signs of something more serious, like extensive root decay.
• Construction, trenches, digging, and other disturbance in the area underneath the canopy of the tree. As we discussed earlier, these can impact the health and the stability of the tree, pending the extent and severity.
• Single or multiple roots lifting out of the ground. This could indicate the tree is slowly tipping, as we discussed earlier.
• Soil that is consistently oversaturated when it had previously been dry. This could be due to a water leak, site change, or some other variable. This can injure or kill a tree that is not used to this sort of saturation. We should determine where this water is coming from and address the issue.

If we find a potential issue in the canopy, on the trunk, with the roots, or in the growing area, it may be necessary to call a trained professional for closer analysis. Generally speaking, most of these issues can be solved through care plans that should include some form of attention to the structure of the tree and the soil in which it grows, at a minimum.

I also want to emphasize that all of this assumes that the tree could harm people or property. If it is in the woods, or in an area where it will not cause harm if it falls, we have nothing to worry about. Leave it for the birds and other life that love dying and dead trees.

Let’s discuss tree structure next.