People often don’t realize a tree or shrub has been girdled until they investigate why it’s losing leaves. By that point, though, it’s often too late.
Right underneath the bark on a tree or shrub is the cambium layer of the plant. This is where the sap flows up and down the plant, taking nutrients from the soil up to the leaves, and taking energy from the leaves down to the rest of the plant. Rabbits and voles will sometimes start feeding on the cambium layer. If they feed on it in a complete circle around the plant, then they have effectively cut off the plant’s circulation. This kills the plant.
Stop this process before animals have gnawed completely around the plant by easily building a small fence to protect the plant from additional damage. Use wire mesh with openings of less than ¼ inch and make a 2-foot-tall cylinder around the plant. Bury the bottom edge about 6 inches deep to keep the animals from burrowing underneath it.
This is also useful if you have an area where you’ve lost trees or shrubs to girdling. When you plant replacements, protect them with fencing.