Q. A buck has done extensive damage to two young red maple trees I planted this past spring. Will covering the damage with pruning sealer help? I don't want to lose them.
A. It is amazing how much buck rub damage trees can survive. Damage that completely encircles the tree's circumference is more deadly than damage up and down. This is because the tree's vascular system is just under the bark. Young trees have very thin bark that offers no protection from such damage. The bright green layer under the bark is called the cambium. It is only a cell or two thick, and it gives rise to the tree's vascular system. When a tree is damaged completely around its circumference, it is said to be girdled. Trees that are girdled often die because they can no longer transport water and nutrients properly. If the damage is most severe up and down on the trunk, the tree can survive, although the growth on that side might be less vigorous than the undamaged side.
Trees are capable of repairing a surprising amount of damage on their own. Avoid the temptation to use pruning sealer. It may make you feel better -- like putting a Band-Aid on the wound -- but it can actually interfere with the tree's ability to heal.
The best practice is to use a sharp knife, such as a grafting knife, to cut off jagged pieces of bark around the edge of the wound. If you can trim the wounds into an elliptical or football shape oriented vertically up and down the trunk, it will help the tree recover more quickly. Do not dramatically enlarge a wound to accomplish this, though. Just clean up the edges as best as you can because they will close over easier than the ragged damage left by the buck's antlers. Prune off any severely damaged limbs.
Protect the trees from stress next year by irrigating during hot, dry weather. Also, protect them from insect and disease damage that could reduce the amount of functional leaf surface. The leaves produce carbohydrates through photosynthesis, and those carbohydrates are critical for the trees to recover from the damage.
Bucks rub their antlers on young, flexible trees in order to rub off the velvet that initially covers them. It is a popular misconception that the drying velvet is itchy and they are trying to get it off -- antlers have no nerve endings. Bucks rub their antlers on trees to attract receptive does and to mark their territory. They also simulate battle with other bucks on these trees, perhaps in order to strengthen their neck muscles in preparation for the real thing.
It is possible that this buck will come back to rub on your trees again, so it is important to take steps to protect them from future damage. You should surround each tree with a sturdy fence or barrier that can keep a determined deer away from the trunk. A 6-foot-tall barrier of welded wire mesh, supported by 8-foot-tall rebar pounded into the ground at regular intervals around the circumference is a reliable way to keep bucks from rubbing on young trees. Another option is corrugated plastic drainpipe that has been slit along its length and placed around the trunk. You can also purchase ornamental metal grates designed for this purpose. They are more expensive but also much more attractive.
Send questions to Sandy Feather by email at firstname.lastname@example.org or by regular mail c/o Penn State Extension, 400 N. Lexington Ave., Pittsburgh 15208.