How To Treat Tree Wounds

Many arborists swear by pruning paint as the best way to treat tree wounds. However, this belief has been disputed for years and it looks like it has been debunked recently.

If pruning paint is not the answer, then how do trees heal? How do they repair their wounds?

This is an analysis on tree wound repair and how to treat tree wounds. After reading, you should be able to understand how trees respond to trauma and how to care for them so that they make a full recovery.

Tree Response To Wounding

Trees must endure all kinds of injuries and attacks throughout their lives. They have to because they are firmly rooted and cannot move to avoid injury.

A healthy, mature forest tree could easily have had thousands of wounds, wounds that could expose the interior of the trunk and hence the rest of the tree to bacteria and fungi, leading to disease, decay, breakage, and death.

To survive, trees must overcome their wounds. But they don’t technically “heal” the wounds, at least not in the way human and animal bodies repair, restore, or replace damaged cells or tissues. 

Trees are built in layers of cells connected by rigid walls in a modular and compartmentalized manner. This structure determines the tree’s response to injury.

During each annual growing season, trees construct their trunks and outer branches  from a layer of actively dividing cells. Cone increments of new wood are added and wrap around the smaller cone increments from the previous year.  

The trees always grow upwards and outwards, both in length and in girth.

Compartmentalization 

Unlike humans or animals, woody plants cannot heal damaged tissue. Instead, they isolate wounds with layers of cells that prevent further damage from spreading called calluses

Unrestricted by the pressure of the bark, the reactive callus cells grow freely at the edges of a wound, forming elongated spirals. These are the areas of new growth that gradually close the wounds, like a branch stump that becomes less and less visible. 

This new growth separates the wood present during the injury from the new wood formed afterwards. But speed and effectiveness of this response varies with tree species and health status.

Development Of Barrier Zones 

Trees are also capable of producing what is sometimes called a reaction or barrier zone, altering the chemistry of the existing wood surrounding a wound and making it inhospitable to decay organisms.

Although these processes are not well understood, the tree tries to avoid further injury by establishing chemical and physical barriers around infected cells, responding to the pathogen, and limiting damage. If the tree is quick and effective with its boundary setting mechanisms, the infection will remain localized and not spread. 

However, if the containment mechanisms are not effective, the infection spreads. Most vigorous or actively growing trees can handle the propagation mechanisms of rot quite successfully.

Read Also: How To Pick The Right Site To Plant A Tree

Care For Tree Wounds

If a tree is injured or suffering from bark loss, there are a few things you can do to heal the wound and improve the appearance of the wound. However, remember that a tree is excellent at containing and compartmentalizing its own wounds in the trunk. 

In most cases, these treatments help very little but they leave the tree looking neat. Put simply, they can change the appearance of a tree as a specimen in the landscape.

Physical Repair

Wounds on trees often appear irregular if the bark tears during the wound. This is common when a branch is broken and when the trunk of the tree is scraped. 

To repair this type of damage, use a box knife to trim off the jagged edges of the bark. Be careful not to remove healthy cortex and expose more living tissue than necessary. 

If possible, the wound should be in the shape of an elongated oval with the long axis running perpendicularly down the trunk or limb. The entire bark around the wound should be taut.

Wound Dressings

Studies have shown that wound dressings may be phytotoxic or not beneficial to trees. They focused on the use of wound dressings to prevent rot fungi from entering trees. 

Vaseline, latex paint, shellac, and asphalt compounds did not promote wound closure. Wound treatments did not inhibit wood staining and some wound dressings damaged trees. 

Cankers have also been linked to petroleum-based tree marking paints, where the solvents kill cambium tissue.

In the past, many people have recommended treating tree wounds. 

Usually the recommendation was to apply tree paint. We now know that covering wounds with paint is harmful, but some continue to recommend the practice and products for tree wounds are still on the market.

Most of these products are petroleum- based (tar, asphalt, paint) and serve only to prevent callus formation and successful compartmentalization. Some of these products can also be used as a food source for fungi. 

Tree wounds are self-healing in most cases and should be subjected to the natural processes outlined above.

Read Also: 13 Signs Your Tree Is Dying

Cavity Filling

If you’ve got a hollow in your tree, first decide whether or not it needs to be filled at all. While it was not an unusual exercise to seal a hollow in a tree trunk with cement, this surely damages the tree. 

Small holes will normally heal and seal themselves naturally. Larger holes might not seal themselves, however they normally are not a trouble for the tree. 

If the tree is hollow and you are concerned that the shape and energy of the tree were compromised, hire an arborist to assess the tree to make certain it is safe.

Filling the cavity is a simple process. Ideally the hole should be as dry as possible, but this may not be possible if the cavity is large or the tree is hollow. 

Although not necessary, you can remove loose debris from the cavity, but do not cut into the wood or hard tissue as this can cause the rot to spread. 

When filling a hole, do not do anything that will cause new wounds in the tree, including drilling a hole in the tree to drain water from a hollow trunk or large cavity. Don’t use stuff like bricks and plaster to fill the hole. 

These materials don’t move with the tree as it grows and changes, which can cause injury inside the tree. Also, water tends to pool between the cement and the tree, promoting rot and disease. 

Rocks and gravel are also not  recommended for tree fills as they allow water to remain in the tree cavity. If the tree needs to be removed, these materials could pose a hazard.

Filling the hole can improve the aesthetics of the tree. But if your goal is simply to keep animals out of the tree, consider covering the hole with chicken wire. 

This will keep larger animals like squirrels and birds away from the tree cavity.

Materials you need:

1. Wire mesh 

2. Insulating foam

Pruning Wounds

Pruning should be done to remove dead, dying and broken branches, to remove low, crossed or dangerous branches; and to control the size of the tree. However, pruning of any kind stresses the tree by removing food-producing leaves if the branch is alive, creating wounds that require energy to seal, and providing potential entry points for disease. 

Pruning should be made to maximize the tree’s ability to close its wound and defend itself against infection. When trimming,  make clean, smooth cuts. 

Do not leave stumps. Leave a small wooden collar at the base of the branch. 

The branch collar is a slightly swollen area where the branch meets the trunk. Cutting the branch flush with the trunk leaves a larger area for callus and a greater chance for decaying organisms to enter the wound. 

The best time for pruning is in winter (dormant period) when temperatures and infection rates are at their lowest and  trees are not actively growing.

Preventing Tree Wounds

Of course, prevention of wounds is the most sensible option in the first place. There are many methods that house owners can practice to avoid wounding and rot of trees. 

First, trees should be planted in the right locations, with good enough area relative to different bushes or obstacles. For example, trees ought to be placed sufficiently some distance away from buildings, sidewalks, driveways, and strength lines. 

Furthermore, making sure that a tree is planted nicely and in a high-quality soil that drains well will go a long way to limit wound recovery problems. If the spot has terrible soil, that soil ought to be amended with composted mulch to enhance conditions for the root system and the tree as a whole. 

Mulching trees additionally discourages the activities of lawnmowers and weedwackers, which can be the usual agents of harm at the bottom of the trunk, for the reason that mulched regions aren’t supposed to develop grass.

The most important thing to remember about urban trees is that while they are beautiful and valuable to homeowners in many ways, they can also pose serious risks if not cared for properly. If homeowners have serious concerns about the stability or health of trees in their gardens, it is wise to consult a professional before taking any action, especially with larger trees. 

This can be easily achieved by contacting local horticulture or trained arborists. Other guidelines to help are:

1. Prune using the right methods at the right time of year and when in doubt always consult a qualified tree trimmer. 

2. Always sterilize your cutting tools with rubbing alcohol or hydrogen peroxide between cuts.

3. Be careful when cutting or trimming around a tree. 

4. Keep your tree well trimmed and remove dead wood regularly to keep it from being susceptible to storm damage.

Final Remarks

While the application of paint, tar or other dressings and fillers is a great temptation for tree lovers around the world, it actually disrupts the normal course of a tree’s wound response and should be avoided. 

Trees need to be sealed and closed, and  they usually do much better without additives. Healthy trees generally recover quickly from injuries. 

Try to keep injured trees growing vigorously by watering and fertilizing them adequately during droughts. If you practice these methods on how to treat tree wounds, you will be able to treat trees effectively.

Frequently Asked Questions