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Monday - September 07, 2009

From: San Antonio, TX
Region: Southwest
Topic: Trees
Title: Decline of mesquite and persimmon trees in San Antonio
Answered by: Barbara Medford

QUESTION:

We have lived in a house in San Antonio for about 30 years now and in the last 5 years, we have seen the decline of several mesquite and wild persimmon trees. I am wondering what would cause their demise! We water infrequently, and have the back yard planted in Hill Country Natives, as suggested by the landscape class at the Center. Overwatering is the only thing I can imagine, besides possibly that they are just at the end of their lifespan..

ANSWER:

We are as puzzled as you are. Usually, when a plant is showing signs of decline, we look at what has changed in the environment, but if you have had these trees in the same spot getting the same care for 30 years, it doesn't seem that anything has changed in the environment. We are pretty sure we can tell you that neither tree has reached its normal lifespan, even though we couldn't find exact figures for either. Prosopis glandulosa (honey mesquite) has a normal lifespan of from 40 to 110 years, with maximum age from 172 to 217 years. Diospyros texana (Texas persimmon) is slow-growing, and ordinarily slow-growing plants have a longer life. Both trees are specified in our Native Plant Database as being drought and neglect tolerant, and with low water use. Both need full sun and good drainage.

So, about the best we can do is speculate. The mesquite has a long taproot to get deep water suppied, as well as a network of roots near the surface. You mentioned over-watering; are these two trees the only plants in your native plant garden suffering similar problems? We know we keep saying this over and over, but it's true that this extreme two-year drought is even causing problems with desert plants. Possibly the water table has dropped so low that not even the mesquite's long taproot can reach its subterranean sources any longer. We trust you haven't been fertilizing the trees; native trees should not need fertilizer, as they should be able to get their necessary nutrients and trace elements from the soil. Don't fertilize, never fertilize a plant under stress. With water rationing being invoked all over Central Texas, perhaps it would be better to just hang on, don't increase watering, and maybe it will rain again sometime.

If other gardeners are having similar problems, hopefully your Texas A&M AgriLIFE Extension Office for Bexar County will have some closer-to-home advice.

Prosopis glandulosa