Protect trees from deer
Q: Iwas at the Chicago Botanic Garden lastweek and sawsome trees with what looked like plastic fencing around their trunks. What is this for, and should I do the same formy trees?
— SueMitchell, Arlington Heights
A: The trees you sawat the Chicago Botanic Garden have fencing around the trunks to protect them from deer rubbing.
Bucks can cause significant damage to young trees in the fall by rubbing their antlers on trunks. Male deer areworking to clean their antlers of summer velvet from early September throughNovember, while also marking their territory during the breeding season.
The bucks will repeatedly strike the tree for noise effect in order to show dominance and intimidate other bucks, and coat the twigs and bark with scent from glands in their face and underbody to mark their territory.
Young trees that are 1 to 5 inches in diameter with smooth bark, such as maples, lindens, birches and magnolias, aremost likely to be damaged by deer rubs. Larger trees with smooth bark, aswell as clump form trees, can also be damaged.
If any of your trees fit those descriptions, then it will most likely be a good idea to protect your trees, as I have seen deer rubbing damage inWinnetka, especially if you live near a park or forest preserve.
Buck territories include many home gardens with young trees. A multistemmed magnoliawas badly damaged by a buck rub inmy front yard in Highland Park last fall, five years after itwas planted.
The damage to trees from buck rubs comes from the shredding of bark froma foot or so above the ground to 3 to 5 feet up the trunk. Young trees have very thin
bark that offers no protection fromsuch damage.
Usually the damage is done over a 24-hour period. The tree’s vascular system — which is just belowthe bark and transportswater, nutrients and food between the roots and leaves— gets damaged, and the underlyingwood is exposed.
If rubbed all theway 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 located vertically on the trunk 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 thewounds into an elliptical or football shape to help the tree recover more quickly, but do not dramatically enlarge thewound to do this.
There is no need to use a wound dressing or to wrap the damage. Smooth edges will 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 magnoliawas completely cut back and restarted due to the extensive branch damage done 2 to 3 feet up
the trunks.
Youwill need to protect the trunks of your maples fromthe ground to about 6 feet up the trunk this fall. It is a good idea to install this protection as soon as you can, as it is already late in the season to do so.
Wrapping with burlap or paper tree wrap will not provide enough protection for deer rubs. Try using a sturdy hardware wire mesh, which is generally available at hardware stores to wrap your tree trunks. Chicken wire will usually work, too, though I knowof a garden where the deer was so aggressive that the chicken wirewas mostly torn off the tree, resulting in 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 hardwarewire mesh, supported by fence posts if you are unable to wrap the trunk due to its small size. Deer repellents will not be effective in controlling buck rubs— you need to get a sturdy physical barrier around the trunks of your trees in order to prevent damage.
Formore plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo @chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.