June 22

1 - Stands of scrub oak may appear dead, but may actually be waiting for moisture to begin growing again.

Yard and Garden June 22, 2013

Q.

On property south of Silver City there are a number of black jack oaks and scrub oaks. They are all looking dead except those in the drainages? Will they come back? I have observed them stressing out there for years.

Judy O.

A.

Many of the oaks that grow in New Mexico grow as scrub oaks. This is a strategy to survive stress. The plant can die back, but then return from an extensive underground system of roots. You said that those in the drainages were looking better, so that suggests drought as the culprit causing the trees to look dead.

Are they dead? They may be alive in part of the above ground stems, or in none of the above ground portions. There is a good chance that there is life in the underground portions waiting for the return of moisture to New Mexico.

To check for life in the stems, skin the stems with a fingernail or a small knife. If, after scratching the bark, you see a green layer just below the bark (the cambium layer); the twig is alive and just waiting for moisture. If the cambium layer is brown, the twig has died back to that point. Work your way down the stem and perhaps you will find a living cambium layer toward the base of the tree, or just below the soil level.

As a scrub oak, the portions in the drainage may be connected to some of the plants higher on the slope. If that is the case, the part of the plant will be helping support at least part of the other plants. Then the chance of returning with moisture is greatly increased.

As you mentioned, the last few years has caused a lot of stress, but we have many adapted native plants that have been through this scenario before. Some will die, some will return. When we have a series of moist years, they will spread. This is the case in many parts of our arid state.

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.

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