Preventing Girdling

matt cogger

Matt Cogger

Horticulture Educator

Ashland and Bayfield County UW-Extension

The days are getting shorter and the trees have lost their leaves. Even though there isn’t any snow on the ground, winter is just around the corner. If you’ve planted young trees and shrubs they may be at risk of girdling. Girdling is usually the result of voles, also known as meadow mice, eating the bark at the base of a tree. The layers of bark include the cambium which moves water and nutrients throughout the tree. If the cambium is destroyed the tree will die since it can’t move water to the leaves and carbohydrates to the roots. The severity of girdling usually increases with the amount of snow cover. The snow protects voles from predators and the elements.

Fortunately there are ways to prevent girdling. Exclusion works well for small plantings. To create a barrier, make a cylinder around the base of the tree using ¼ inch mesh hardware cloth. Leave a couple inches between the cylinder and the tree or shrub so it has room to grow. The cylinder should be buried two to three inches below the soil and extend at least 18-20 inches above the ground. In regions that have heavy snowfall you may need to increase the height of the cylinder. If the hardware cloth is buried by the snow the voles will just climb over the top of the barrier. You may have heard that packing the snow around young trees and shrubs will also discourage voles. Packing the snow can help to keep the hardware cloth above the snowline, but will not prevent voles from reaching a plant.

There are numerous predators of voles such as hawks, owls, foxes, and snakes. Keeping the area around your trees free of tall grass or other places for voles to hide from predators in the summer will help to discourage population build up near your trees and shrubs. Mouse traps also work to control voles in small areas. Management of voles is best accomplished through habitat modification, natural predators, and physical barriers around trees and shrubs. By planning ahead before the snow you can prevent your trees and shrubs for being girdled by voles.

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