Some of my friends had minor damage from deer rubs to the trunks of a couple of their maple trees last fall. Should I be worried about this happening in my garden and what can I do to protect my trees?
— Jacob Jenson, Highland Park
Bucks can cause significant damage to young trees in the fall by rubbing their antlers on trunks. Male deer do this to clean their antlers of summer velvet from early September through November while also marking their territory during the breeding season. The bucks repeatedly strike the tree for the noise effect to show dominance and intimidate other bucks and coat the twigs and bark with scent from glands in their faces and underbodies to mark their territory. Young trees that are 1 to 5 inches in diameter with smooth bark (such as maples, lindens, birches, and magnolias) are most likely to be damaged by deer rubs. Larger trees with smooth bark as well as clump-form trees can also be damaged. Unfortunately, buck territories currently include many home gardens with young trees. A multi-stemmed magnolia was badly damaged by a buck rub in my front yard in Highland Park last fall, five years after it was planted. Your trees are at risk of further damage this fall.
The damage to trees from buck rubs comes from the shredding of bark from a foot or so above the ground up to 3 to 5 feet up the trunk. Young trees have very thin bark that offers no protection from such damage. Usually, the damage is done over a 24-hour period. The tree’s vascular system, which is just below the bark, transports water, nutrients and food between the roots and leaves. This system can be damaged, and the underlying wood is exposed. If rubbed all the way around, the trunk can be effectively girdled, resulting in the eventual death of the tree in one to three years. If the damage is mostly vertical and does not go all around the trunk, the tree can survive, although it may die on the side where the damage occurred.
Trees can heal after a surprisingly large amount of damage. Trim off any loose, shredded bark where it’s not connected tightly to the trunk. If possible, cut the wounds into an elliptical or football shape to help the tree recover more quickly, but do not dramatically enlarge the wound to do this. There is no need to use a wound dressing or to wrap the damage. Smooth edges heal better than the ragged edges left from the deer rubbing. Prune back broken branches as needed. Small clump-form trees can be ruined if too many branches are broken. My magnolia needed to be completely cut back and restarted due to the extensive branch damage done at 2 to 3 feet up the trunk.
Protect the trunks of your trees from the ground to about 6 feet up the trunk this fall. It is a good idea to install this protection soon. Wrapping with burlap or paper tree wrap generally does not provide enough protection for deer rubs. Try using a sturdy hardware wire mesh that is available at hardware stores to wrap your tree trunks. Chicken wire usually works too, though I know of a garden where the deer was so aggressive that the chicken wire was mostly torn off the tree with heavy damage to the bark. There are plastic tree wraps that should also work. Surround a small tree with a 6-foot-tall barrier of hardware wire mesh supported by fence posts if you are unable to wrap the trunk due to its small size. Deer repellents are not effective in controlling buck rubs — you need to get a sturdy physical barrier around the trunks of your trees to prevent this kind of damage.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at email@example.com. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.