Issue: April 18
Grafting may help a wounded apple tree
Q. I have an old apple tree in my small orchard that I am worried about. It makes very delicious apples, but sometime in the past it must have been hit by something. The tree is leaning and the bark on one side has peeled off, revealing the dry wood underneath it. The wood is cracking now and I am worried that I will lose the tree. Can I paint the wood? Will that help?
A. Injury to the bark of a tree can cause the symptoms you described. The cracking of exposed wood is the result of that wood drying out. You can paint it with white latex (water-based paint). That will slow the drying, but will not heal the wound. The wound will persist as long as the tree lives.
An apple tree is fairly tolerant of these kinds of injuries and will live for a long time with exposed wood resulting from injuries, but this is not an ideal circumstance. You can help the tree to close the wound by a process called repair grafting or bridge grafting. This will allow healthy wood to grow over the wound and enclose (compartmentalize) the injury. It will also help restore the vascular connections that carry minerals and water from the soil to the leaves and food from the leaves to the roots. To accomplish this grafting process you can select from the same tree some long twigs that will bridge the wound. Then by grafting the base of the twig into the healthy tissue below the wound and into the healthy tissue above the wound, the process of wound closure can be speeded. It is important to maintain the proper orientation of the twigs. The upper (distal) portion of the twig must be grafted at the top and the lower (proximal) portion should be at the base of the bridge graft.
Another way to employ grafting to save this variety of apple is to graft buds or twigs from this tree onto other nearby, healthy trees, or onto seedlings in the orchard to replace the wounded tree when it finally dies. If you graft this variety onto another tree, your tasty variety will not be lost, even if the original tree dies.
For more gardening information, visit the NMSU Extension publications World Wide Web site at http://aces.nmsu.edu/pubs/_h.
Send your gardening questions to:
Yard and Garden, Attn: Dr. Curtis Smith
NMSU Agricultural Science Center
1036 Miller Rd. SW
Los Lunas, NM 87031
Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State Universitys Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating.