March 26, 2011

1 - Many broadleaf evergreen (including pyracantha) plants were injured by this winter's cold weather. Wait and see if they can produce new growth before removing them.

Yard and Garden - March 26, 2011


I heard somewhere recently that pyracanthas were damaged by the frost but will come back in time. Mine are 40 years old, huge like trees and all 30 of them look dead. Are they likely to return or do I have to have them cut down?

- Judy C.


It is possible that the pyracantha plants were killed, but it is unlikely. The leaves of many broadleaf evergreen plants were injured and have turned brown or black. The twigs may have been injured, but buds on the larger branches and trunks have probably survived. You will not know for sure until later this spring when new growth begins. New growth may occur later than usual because of the injury. After growth has developed and you see which twigs and branches (if any) were killed, you can prune them back to healthy growth. This just requires waiting and some irrigation to provide water for the new growth. Without leaves, however, less water than usual is needed, but his has been a very dry winter.

2 - Other injuries, such as herbicide damage, may also appear after this cold winter


I have a globe willow tree that is 23 years old. Last summer it came out with leaves all over, and then about the 1st of June all the leaves on half of the tree shriveled up and turned brown. They did have a little green in them so we thought that this happened because we put "weed and feed" on the lawn and it burned the tree. This spring the tree came out but the side that had issues last summer did not come out at all. It looks dead. We do not know what to do. Should we prune the dead limbs off or cut the tree down? It is a huge tree and we need the shade but we do not want it to look ugly. Do you think there is any hope for our tree?

- Jana T.



While many questions like yours have dealt with the extreme cold weather New Mexico experienced this winter, you have given information that directs our attention to another cause. The products containing fertilizer mixed with post emergence herbicides can cause the symptoms and death of all or part of trees. The directions on the package usually state "do not use within the root zone of desirable trees and shrubs." This root zone extends much farther than many people realize, so problems can develop. The root zone of an established globe willow tree can extend to at least 4 times the height of the tree outward in all directions. The symptoms you described from last summer are consistent with herbicide damage. The first growing season, the branches may not appear to be killed, but in the second season, the extent of the twig/branch death will become evident.

There is still a chance that the tree has living buds on some of the larger branches, so you can wait until about June to determine the extent of the dieback. At that time, you can determine if pruning the damaged branches will leave a tree that is unacceptably ugly, requiring tree removal, or if you will be happy with the appearance of the tree. Pruning dead and severely weakened branches in June will not harm your tree. Your local NMSU Extension Service County Agent can help you determine the extent of the damage and give on-site advice regarding this tree.

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:, office: 505-865-7340, ext. 113.


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

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