December 12, 2015

1 - Deciduous trees may be pruned now that they have entered dormancy.

Yard and Garden December 12, 2015

Q.

Leaves have fallen from most of my deciduous trees. Is it time to prune these trees now? Can I prune my roses as well?

A.

Now that the trees have become dormant for the winter you can begin pruning deciduous trees, but you should wait until late winter or early spring to prune roses (and grape vines). Conifers may also be pruned, but by removing branches that were protecting interior branches and needles, you may increase winter injury and desiccation to the previously protected branches.

Some gardeners prefer to wait until late winter to prune their fruit trees because the tree will begin growing fairly soon after pruning to close the wound caused by pruning. Pruning cuts made in late fall and early winter must wait until spring for the wound closure process to close the pruning wound. Until the wound closes the end of the pruned branch is subject to drying, but most trees can survive this even in the arid conditions of New Mexico. If you have many trees to prune it makes sense to begin pruning early and waiting for spring for closure of the pruning wounds. If you have only a few trees to prune, you may prefer to wait until late winter to prune your trees.

Remember not to prune excessively. Food for growth next spring is stored in the branches and trunk. If you over-prune you will weaken your tree and reduce growth next year. A young, vigorous tree may be pruned to remove from 25 to 33 percent of the living branches and twigs, but you do not have to remove that much. Older trees will tolerate removal of an even lower percentage of the living branches and twigs. In older trees, proper pruning will involve more removal of dead and weak branches and less removal of health branches.

Most of the commonly grown roses and grapes may begin growth if there is warm weather after pruning, so they should not be pruned until late winter. A good guide for pruning roses is to wait until less than one month before the expected last frost in the spring. That may be as early as February in Southern New Mexico and as late as mid-May in Northern New Mexico and at high elevations. By delaying pruning, any growth stimulated by pruning will occur closer to that last frost and, hopefully, at temperatures that will not kill the new growth.

This is a good time for the advice I have given for years about pruning: Do not top trees and make proper pruning cuts. Proper pruning cuts involve taking care to prune a branch in a way that leaves the branch collar at the base of the branch being removed. This is important for permitting the tree to protect itself from entry of disease through the pruning wound. More information about pruning is available at ACES Publications.

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: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!