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The term “girdling” can refer to a number of things, including a gem cutting technique and the wearing of shaping garments by women. In this particular wiseGEEK article, “girdling” is being used in the sense of a horticultural practice which involves trees. Tree girdling occurs when a strip of bark around a tree's circumference is removed. This practice will ultimately cause death for the tree, and it is not generally recommended.
Trees use their bark to transport nutrients. When a strip of bark is removed, the tree cannot move certain nutrients up and down, and it will slowly die off. Death is prolonged because the trunk of the tree can be used to transport some nutrients, so the tree will survive until deficiencies in sugars start to set in. Tree girdling usually happens by accident, although it is sometimes utilized in forestry management.
Some trees become girdled when they are tethered to supportive stakes as they grow. The tether eventually pulls tight against the trunk of the tree, killing off the bark. Girdling can also occur when fencing and other materials become embedded in the bark, or when people accidentally damage a tree with lawn mowers, weed eaters, and other gardening tools. To prevent mechanical damage to trees, mulching the area around a tree can be a good idea, preventing the need to run weed-trimming equipment right up against the trunk of a tree.
Insect damage can also result in girdling. In these instances, beetles and other pests eat away at the bark from underneath, eventually forcing a strip to pull away and girdling the tree. Animals such as bears have also been known to girdle trees by accident. People sometimes inadvertently cause girdling when they wrap trees to protect them from pests or mechanical equipment.
Tree bark removal can also be done deliberately with the intent of causing tree death. Girdling is sometimes used in forestry management where traditional felling techniques would be disruptive. Some cultures have also used girdling as a felling technique historically, allowing the tree to die and dry out while standing upright so that it can be easily harvested and transported. However, many trees rot after being girdled, so this practice is not advised. Dead trees can also fall in unpredictable ways during storms, potentially causing damage on their way down.
In orchards, girdling is sometimes used to manage fruit size and sugar content. By girdling specific branches, farmers can force a tree to produce especially large fruits with a high sugar content.
Girdling crabapple trees is an excellent way to control how much fruit they produce. My grandfather actually had a technique he used that would limit the amount of crabapples produced, and how much fruit they would dump on our lawn.
While my family liked the crabapple tree, it wasn't very much fun picking up rotted fruit. Choosing branches to girdle actually really helped reduce our workload. I suppose I feel a bit bad about choking off the nutrients to certain parts of the tree, but it just seems cheaper than removing a tree. Also, I know there is free tree removal in some cities, but I don't think we're that lucky.
When we bought our home we made the mistake of putting in a new fence too close to our tree and part of the fence actually ended up embedded in the bark. We had no idea that girdling a tree by accident would damage it, and we felt terrible over the damage to our willow tree.
Unfortunately it turned out the cost to remove tree roots and then removing the tree was cheaper than taking down the fence we had in place. My wife was pretty mad though that her little willow tree ended up biting the dust. I guess I will have to make it up to her by planting a new willow tree in a safe spot.