June 27, 2015

1 - There are several potential causes for dying branches, but summer is a good time to remove them while they are obvious.

Yard and Garden June 27, 2015

Q.

Some of my trees are looking pretty unhealthy. After the rains this spring I expected the trees to be full of leaves. Some trees look OK, but some have some branches with only a few clusters of leaves. What can I do? Should I prune these trees? When can I prune them?

A.

The moisture much of the state received was very helpful, but this was following some dry times. If the trees were already injured by the previous years of drought, you may be seeing that damage appearing. Trees often respond slowly to damaging stress. The fact that it is producing leaves is good and a sign of hope.

Other factors that could be involved are the temperatures and potential insect damage. Many parts of New Mexico experienced a period of unusual warmth in February followed by a return of cold weather and typical oscillations between warm and cold. Some trees will more quickly begin preparations for growth than others. They will reduce the hardiness of their flower and leaf buds and may become sensitive to damage when the cold weather returns. That can also lead to spotty development of leaves in the tree. If there is a pattern of poor leaf development this may be the case. Branches in a warmer location, perhaps over gravel mulch, driveway, street, parking lot, or on the south side of the tree will experience earlier warming. These portions of the tree may exhibit injury by loss of bud hardiness and the cold temperature conditions that followed.

Any stress to a tree, drought or freeze injury, can make the tree more attractive to insects. There may be existing or new insect infestations due to past environmental stresses.

As you look at your tree and consider which of the above factors, or perhaps something else, has impacted your tree, you determine if pruning would be helpful. If the problem is past drought injury and the branches and twigs at the ends of branches are dry and crisp, they can be pruned. If there are signs of insects, pruning may be indicated, but you should collect samples of the damaged branches and insects, if possible, and take them to your local NMSU Cooperative Extension Service office to have them identified. With identification you will have a better idea as to whether pruning would be helpful. Your Extension Service Agent can help you make that determination.

If the branches and twigs beyond the leaves that are developing still have a green cambium (the layer just under the bark), you may want to wait and see if any growth develops later this summer. Proper irrigation and a good monsoon may help with this.

Anything that is dead or weak can be pruned from the tree now. In fact, pruning dead and weak parts of the tree is easiest during the summer because these branches are most easily identified during the summer. Weakly growing branches are consumers of energy produced in the rest of the tree, so their removal allows the tree to direct that energy into areas with healthy growth.

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!