Responding to Frost Bite: A Love-Wait Relationship

County Cooperative Extension Service Agents and Specialists across the state are fielding questions about cold injury on landscape plants and orchard trees and what to do about it. The low temperatures in mid-February didn’t break many records for us in New Mexico. Other parts of the region were hit badly. My cousin in San Antonio, Texas, shared a photo of the huge sago palm in her yard that looks like it saw a ghost—in just a few freezing days, all of the dark green fronds turned an unnatural off-white color. This recent arctic blast reminded many New Mexicans of the deep freeze of February 2011. I searched the Southwest Yard & Garden column archives and selected excerpts written 10 years ago by my predecessor Dr. Curtis Smith, with helpful advice on dealing with frost damage. Spoiler alert: There are no quick fixes. For now, just water and wait. That’s why I’m calling it a “love-wait relationship.”

March 5, 2011: Column by Dr. Curtis Smith

Question:

Our wax leaf ligustrum leaves have turned a brown color, probably from the terrible cold we all experienced. Is it likely dead, or do you recommend trimming it back and waiting to see whether it is still alive at the core and roots? It’s about 5 feet tall. We moved it about 3 years ago, and I fussed over it after the move because we had to cut part of the taproot off. This is a tough plant with a desire to survive, I think. - Barb R., Alamogordo

Answer:

Ligustrum japonicum, the wax leaf ligustrum, is one of many broadleaf evergreen plants that suffered damage this winter. Wax leaf ligustrum is listed as hardy in USDA hardiness zone 8 and warmer. You live in zone 8, but this year the temperature probably dropped below the expected 10°F low. Your ligustrum probably survived, but some of the twigs and branches may have been killed by the cold. If the shrub needs pruning, you can trim it back now. However, since you may not be able to easily determine which branches were damaged, you can also wait until new leaves begin to form and prune out branches that do not exhibit new, healthy growth.

There is a chance that your wax leaf ligustrum and those of other gardeners were killed. If these shrubs were planted on the north side of a house where it was colder and remained colder longer, the temperatures may have been fatal. Even if these plants were not killed, the branches may have been killed further down the plant and will probably begin growth later than usual.

Other broadleaf evergreen shrubs have been damaged in New Mexico this year. Photinia shrubs, which are rarely damaged by cold winters, except this year, are also exhibiting brown leaves. The advice to wait before cutting them down is relevant for them as well. This spring, the virtue of patience will be more valuable than usual.

Snowy neighborhood in Los Lunas. It’s too early to tell which plants were damaged by the cold this winter. Photo credit Marisa Thompson

March 26, 2011: by Dr. Curtis Smith

Question:

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.

Answer:

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 this has been a very dry winter.

April 30, 2011: by Dr. Curtis Smith

Question:

My Mexican elder trees do not have any leaves on them, but several of them have a lot of shoots growing from the trunk near the ground. In the past I have removed the shoots to encourage growth in the canopy (or so I thought that would work). Is that the right thing to do?

- Barb D., Las Cruces

Answer:

It is usually a good idea to remove the new shoots forming at the base of a Mexican elder, desert willow, or other tree that tries to be a shrub by producing numerous basal shoots. However, this year some of these trees may have lost twigs and even branches (perhaps trunks) to the extreme cold. Even if new growth develops, it may be weak and may eventually die back. The lower sprouts may be necessary to save the trees.

In some cases, the renewed plant may appear to be a shrub for a few years. After a couple of years, you can select one or a few healthy sprouts to become the new trunk. For now, it may be wise to let the basal shoots grow until you know how much damage occurred in the upper portions of your tree.

Visit our 25 years of NMSU Southwest Yard & Garden column archives.

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 and the NMSU Horticulture Publications page.

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!