TO Wrap or NOt to Wrap Your Trees
To wrap or not to wrap…your trees
If you have ever purchased a tree from a nursery or seen people wrapping trees in paper or plastic tubes, you may have found yourself wondering why people wrap the trunks of trees. There are many reasons given for wrapping tree trunks, and those reasons can be broken down into a three basic categories.
There are plenty of reasons to protect trees. Most of us have seen the evidence of chewed bark, a nick from a lawn mower or damage after a wind or ice storm. So, does wrapping your tree really protect the trunk from people, animals, and weather?
First a few definitions:
The usual concern when tree trunks are damaged is whether the damage was deep enough to cut through to the cambium. If only small sections or pieces of bark are injured, rarely are there any serious issues. However, on young or mature trees with thin bark it does not take much to go from cutting the bark to cutting into the cambium; the larger the wound, the larger the problem. Unlike people, when trees are cut they don’t yell or cry out or bleed. Trees just stand there and take it, but beneath the surface of the wound the tree is doing its best to form walls around the wound. This is referred to as compartmentalization.
Trees don’t scab over
Contrary to common perception trees don’t heal. What trees do is compartmentalize, which means that they form cellular walls all around a wounded area in order to protect the rest of the tree from decay or outside harm. The part of tree that has been wounded stays that way for the remainder of the tree’s life. Healthy trees can seal off the affected area and grow new tissue around the damage, but the damage has been done. That’s why you can see things like old knots in wood that are usually a different color than the surrounding wood. The branch was removed while the tree was still living and the tree grows over the wound. Some tree species compartmentalize better than others. Poor compartmentalization of wounds can lead to serious tree decay and hazardous situations.
Knowing once a tree is wounded it is wounded for life gives a great incentive to protect trees. If a branch is wounded it can easily be removed without too much stress on the tree, but if the trunk is wounded it’s difficult to remove the trunk without drastically affecting the growth and appearance of your tree. Young trees, like kids, can be hurt more easily, but they can also recover well if they are kept healthy.
So, how do you protect your tree’s trunk?
There many types of tree wraps or protection devices used to protect tree trunks. These materials can be grouped into broad, yet descriptive, categories: non-reflective and non-insulating wraps (i.e., paper), reflective wraps, insulating wraps, reflective and insulating wraps, paints and whitewashes, barriers, and homemade protection devices like a leaning board. These products are widely available and can be purchased for a variety of prices.
In order to answer the question of effectiveness for various protection devices, consider the first two protection categories. Damage to tree trunks from people and animals are similar in that they require usually require getting close to the trunk of the tree. If the bunny is never in your yard, it will never chew the bark off your tree. As you can probably imagine, wrapping a tree in kraft paper is more like wrapping the tree in gift wrap for the bunny than it is protecting the trunk. When installing protective measures against bunnies and the neighborhood lawn service, a barrier of some kind is a better approach than a tight wrap.
Barriers can be seasonal or situational. Most critter damage to the bark and cambium on tree trunks happens during the winter months. Fencing can be installed at a safe distance of at least several inches from the trunk and up to a few inches past the anticipated snow line. Fencing can be installed in the fall and removed in the spring once there are better things for bunnies to eat, like your neighbor’s garden. If you are only protecting against animal damage, avoid any device or structure that presses or rubs on the trunk, this can cause damage from a rapid fluctuation in temperature and moisture to abrasions on the bark. Similar items can be used when doing any work near the tree.
A mulch ring around the tree is an excellent solution for lawn mowers and trimmers that can get too close, causing unintended cases of lawn mower blight. The mulch should be spread a fewer inches thick and kept from touching the trunk of the tree. Mulch helps to create an attractive barrier that has the dual benefit of retaining moisture over the tree roots.
The last protection category is more complicated and there are lots of differing opinions on the topic of damage from seasonal effects. There are two seasonal effects that are frequently described and debated over: frost cracks and sunscald. In order to protect trees from frost cracks and sunscald, people and companies have come up with many products. Until recently there was little research or conflicting research as to which products actually protected trees. The key to choosing the correct method of protection is to first understand the root cause of the problem.
Frost cracks are vertical splits in bark, cambium, and wood of the tree, usually starting near the base of trunk and progressing up into the tree. They are start at an existing wound site and when a rapid change in temperature creates internal stress resulting in a fracture. These cracks can start small becoming longer and deeper over time. Here, the pre-existing condition is the root cause of the problem; the cold temperatures simply exacerbate the issue. The key is prevention; using mulch around the base of a tree is a cheap and easy way to prevent wounds near the base of tree. Frost cracks can be seen on any side of the tree.
Sunscald is the death of bark and cambium due to rapid changes in temperature. The damage is not always easy to see. The bark and cambium die causing the bark to become detached from the trunk. The bark will usually crack or peel off, but the damage has already been done at that point. The key to sunscald is always prevention. Sunscald can be caused by a variety of predisposing issue, but the most common appears to be stressed from a lack of water going into the winter season. Watering trees in the fall is the cheapest and easiest way to prevent sunscald. However, as with any method this is not 100% effective. Use of tree wraps for vulnerable trees may still be warranted. Young, thin barked, or newly planted trees maybe at a higher risk than trees that are better established.
Research shows that the best wraps are those that reduce temperature changes for vulnerable thin barked trees. Researchers found that of all the wrap options previously mentioned, the best ones were the wraps that both insulated the trunk and reflected the sun’s rays.
Proper application of the wraps is still very important. Wraps should be applied starting the base of the tree then continue to the first branch and should be installed in late fall. Removal of the wraps should be completed in late winter while the sun light is still minimal. This helps the trunk of the tree to gradually adjust to the increasing sunlight. If the wrap is applied to loosely to it may actually cause greater fluctuations in temperature at the trunk surface. Moisture build up is another concern with loosely applied wraps.
The real problem to be solved in all of these cases is the prevention of the initial injury or stress condition. This can be as simple as mulching around the tree and keeping the tree well watered throughout the summer and into the fall. Newly transplanted trees will generally need the most attention as they will likely have damaged or reduced root system. Care in planting and maintaining your trees should provide years of enjoyment and benefits.
For More Information
Appleton, B. L., & French, S. (1992). Currtent attitudes toward and uses of tree trunk protective wraps, paints and devices. Journal of Arboriculture , 18 (1), 15-20.
International Society of Arboriculture. (2009). Glossary of arboricultural terms. Champaign, IL: Dixon Graphics.
Kubler, H. (1983). Mechanism of frost frack formation in trees--a review and synthesis. Forest Science , 29 (3), 559-568.
Litzow, M., & Pellet, H. (1983). Materials for potential use in sunscald prevention. Journal of Arboriculture , 9 (2), 35-38.
Roppolo Jr., D. J., & Miller, R. W. (2001). Factors predisposing urban trees to sunscald. Journal of Arboriculture , 246-254.
Syndor, T. D. (2004). School of environment & natural resources. Retrieved March 2011, from Ohio State University school of environment & natuarl resources: http://senr.osu.edu/current/courses/ENR232/Tree_Wrap.pdf
If you have ever purchased a tree from a nursery or seen people wrapping trees in paper or plastic tubes, you may have found yourself wondering why people wrap the trunks of trees. There are many reasons given for wrapping tree trunks, and those reasons can be broken down into a three basic categories.
- Protection from people (e.g., construction activity, moving trees, chemical sprays)
- Protection from animals (e.g., any critter that likes to chew on bark)
- Protection from seasonal effects (e.g., cold temperatures and sun)
There are plenty of reasons to protect trees. Most of us have seen the evidence of chewed bark, a nick from a lawn mower or damage after a wind or ice storm. So, does wrapping your tree really protect the trunk from people, animals, and weather?
First a few definitions:
- Photosynthesis – the process that green plants use to convert the energy given off by the sun to food for the plant. This process is accomplished by the green parts of the plant, usually the leaves, but any part of the plant that is green can photosynthesize. Basically it’s nature’s way of solar-powering plants.
- Bark – seems obvious, it’s the outer layer of the tree. Similar to human skin, the bark of a tree serves to protect the inner tree from the outside world. The bark on most young trees is thin and can actively photosynthesize, although less than the leaves of the tree. Bark comes in all kinds of textures, colors, and thicknesses.
- Cambium – this is the living tissue of the tree. The cambium is very thin, in most cases it is only a few cells thick and it lies just beneath the bark. If enough of the cambium on a branch or trunk is damaged the tree or branch may die. Any damage to the cambium will cause stress in the tree, which affects a tree’s ability to grow new tissue over wounds, survive times of drought or insect attack.
The usual concern when tree trunks are damaged is whether the damage was deep enough to cut through to the cambium. If only small sections or pieces of bark are injured, rarely are there any serious issues. However, on young or mature trees with thin bark it does not take much to go from cutting the bark to cutting into the cambium; the larger the wound, the larger the problem. Unlike people, when trees are cut they don’t yell or cry out or bleed. Trees just stand there and take it, but beneath the surface of the wound the tree is doing its best to form walls around the wound. This is referred to as compartmentalization.
Trees don’t scab over
Contrary to common perception trees don’t heal. What trees do is compartmentalize, which means that they form cellular walls all around a wounded area in order to protect the rest of the tree from decay or outside harm. The part of tree that has been wounded stays that way for the remainder of the tree’s life. Healthy trees can seal off the affected area and grow new tissue around the damage, but the damage has been done. That’s why you can see things like old knots in wood that are usually a different color than the surrounding wood. The branch was removed while the tree was still living and the tree grows over the wound. Some tree species compartmentalize better than others. Poor compartmentalization of wounds can lead to serious tree decay and hazardous situations.
Knowing once a tree is wounded it is wounded for life gives a great incentive to protect trees. If a branch is wounded it can easily be removed without too much stress on the tree, but if the trunk is wounded it’s difficult to remove the trunk without drastically affecting the growth and appearance of your tree. Young trees, like kids, can be hurt more easily, but they can also recover well if they are kept healthy.
So, how do you protect your tree’s trunk?
There many types of tree wraps or protection devices used to protect tree trunks. These materials can be grouped into broad, yet descriptive, categories: non-reflective and non-insulating wraps (i.e., paper), reflective wraps, insulating wraps, reflective and insulating wraps, paints and whitewashes, barriers, and homemade protection devices like a leaning board. These products are widely available and can be purchased for a variety of prices.
In order to answer the question of effectiveness for various protection devices, consider the first two protection categories. Damage to tree trunks from people and animals are similar in that they require usually require getting close to the trunk of the tree. If the bunny is never in your yard, it will never chew the bark off your tree. As you can probably imagine, wrapping a tree in kraft paper is more like wrapping the tree in gift wrap for the bunny than it is protecting the trunk. When installing protective measures against bunnies and the neighborhood lawn service, a barrier of some kind is a better approach than a tight wrap.
Barriers can be seasonal or situational. Most critter damage to the bark and cambium on tree trunks happens during the winter months. Fencing can be installed at a safe distance of at least several inches from the trunk and up to a few inches past the anticipated snow line. Fencing can be installed in the fall and removed in the spring once there are better things for bunnies to eat, like your neighbor’s garden. If you are only protecting against animal damage, avoid any device or structure that presses or rubs on the trunk, this can cause damage from a rapid fluctuation in temperature and moisture to abrasions on the bark. Similar items can be used when doing any work near the tree.
A mulch ring around the tree is an excellent solution for lawn mowers and trimmers that can get too close, causing unintended cases of lawn mower blight. The mulch should be spread a fewer inches thick and kept from touching the trunk of the tree. Mulch helps to create an attractive barrier that has the dual benefit of retaining moisture over the tree roots.
The last protection category is more complicated and there are lots of differing opinions on the topic of damage from seasonal effects. There are two seasonal effects that are frequently described and debated over: frost cracks and sunscald. In order to protect trees from frost cracks and sunscald, people and companies have come up with many products. Until recently there was little research or conflicting research as to which products actually protected trees. The key to choosing the correct method of protection is to first understand the root cause of the problem.
Frost cracks are vertical splits in bark, cambium, and wood of the tree, usually starting near the base of trunk and progressing up into the tree. They are start at an existing wound site and when a rapid change in temperature creates internal stress resulting in a fracture. These cracks can start small becoming longer and deeper over time. Here, the pre-existing condition is the root cause of the problem; the cold temperatures simply exacerbate the issue. The key is prevention; using mulch around the base of a tree is a cheap and easy way to prevent wounds near the base of tree. Frost cracks can be seen on any side of the tree.
Sunscald is the death of bark and cambium due to rapid changes in temperature. The damage is not always easy to see. The bark and cambium die causing the bark to become detached from the trunk. The bark will usually crack or peel off, but the damage has already been done at that point. The key to sunscald is always prevention. Sunscald can be caused by a variety of predisposing issue, but the most common appears to be stressed from a lack of water going into the winter season. Watering trees in the fall is the cheapest and easiest way to prevent sunscald. However, as with any method this is not 100% effective. Use of tree wraps for vulnerable trees may still be warranted. Young, thin barked, or newly planted trees maybe at a higher risk than trees that are better established.
Research shows that the best wraps are those that reduce temperature changes for vulnerable thin barked trees. Researchers found that of all the wrap options previously mentioned, the best ones were the wraps that both insulated the trunk and reflected the sun’s rays.
Proper application of the wraps is still very important. Wraps should be applied starting the base of the tree then continue to the first branch and should be installed in late fall. Removal of the wraps should be completed in late winter while the sun light is still minimal. This helps the trunk of the tree to gradually adjust to the increasing sunlight. If the wrap is applied to loosely to it may actually cause greater fluctuations in temperature at the trunk surface. Moisture build up is another concern with loosely applied wraps.
The real problem to be solved in all of these cases is the prevention of the initial injury or stress condition. This can be as simple as mulching around the tree and keeping the tree well watered throughout the summer and into the fall. Newly transplanted trees will generally need the most attention as they will likely have damaged or reduced root system. Care in planting and maintaining your trees should provide years of enjoyment and benefits.
For More Information
Appleton, B. L., & French, S. (1992). Currtent attitudes toward and uses of tree trunk protective wraps, paints and devices. Journal of Arboriculture , 18 (1), 15-20.
International Society of Arboriculture. (2009). Glossary of arboricultural terms. Champaign, IL: Dixon Graphics.
Kubler, H. (1983). Mechanism of frost frack formation in trees--a review and synthesis. Forest Science , 29 (3), 559-568.
Litzow, M., & Pellet, H. (1983). Materials for potential use in sunscald prevention. Journal of Arboriculture , 9 (2), 35-38.
Roppolo Jr., D. J., & Miller, R. W. (2001). Factors predisposing urban trees to sunscald. Journal of Arboriculture , 246-254.
Syndor, T. D. (2004). School of environment & natural resources. Retrieved March 2011, from Ohio State University school of environment & natuarl resources: http://senr.osu.edu/current/courses/ENR232/Tree_Wrap.pdf
