1 - Grafting a broken branch back is not impossible, but very difficult.
Q. Our Mexican Alder trees broke off in last night's storm. Is there any way to repair this?
A. If the branch broke OFF (totally or mostly off), it would be best to just prune it properly from the tree. If it broke, but is mostly still attached, it may be possible to graft it back. This may not work, but may be worth a try.
As soon as possible so that the critical cambium layer does not dry and die, put the branch back into place and with bolts or large lag screws, reattach the branch. If the cambium layer (just under the bark) has dried, you should rewound the layer by carefully scraping away or shaving away a thin layer of the dry tissue to reveal healthy, moist tissue. Immediately put this back into contact with the matching layer (probably also shaved) and hold it tightly together.
Do not tie it with rope or chain. Use the screws or bolts to tightly hold the branch into place so that the cambium layers in the branch and the trunk are held together. Do not wrap rope or other material (chain, tape, etc.) around the trunk to avoid girdling the tree. However, it may be good to coat the wounded region with grafting wax, or a sheet of plastic (for a few weeks) to keep the wound region from drying. Remove any material wrapped around the trunk periodically and then reapply it to prevent girdling. At the end of the growing season remove any plastic wrap permanently.
If the graft failed, you can then properly prune the branch from the tree. You should need no pruning paint, but if you want to cover the wound, you can use a light colored (white) latex paint.
Another option is to bridge graft. That is to take a small branch from the same tree and graft it across the wounded area. There is not room in this article to describe the technique in detail, but it is described well in many books about grafting and plant propagation. Such books are available in many libraries. This information is also available on the internet.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!