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Sunday - May 02, 2010

From: Austin, TX
Region: Southwest
Topic: Pruning, Watering, Trees
Title: Failure to thrive of Texas Mountain Laurel in Austin
Answered by: Barbara Medford

QUESTION:

I have an adult (over 25 years?, 20 feet tall?) Mountain Laurel next to my house in Austin. The winter of 2009/10 it lost most of its leaves. It did bloom and leaf out this Spring--not vigorous especially, not on the top. Is it completing its life span indicating I should take it down and replace it? Or, should I give it another year or two to see if it comes back? Possibly resulting from a combination of the drought and extreme 2009 winter weather. I don't see similar specimens in my neighborhood in similar condition. Thank you for your advice.

ANSWER:

Sophora secundiflora (Texas mountain-laurel) is native to the Austin area, so we can't blame the problems on it being out of its territory. You are absoutely correct that even native plants, well adapted to our uncertain climate, have suffered this past couple of years. However, everything we looked at researching this plant says that its mature height is 10 to 15 ft., but none of the material said how old it was expected to get. Generally speaking, the slower a plant grows, and this one grows very slowly, the longer it will live. So, it would seem your tree is mature, but not necessarily senile, ready to die. The only possible change we can think of that might cause some decline in a tree that well developed is if there has been a change in the drainage. This is a plant accustomed to growing in desert areas and limestone, which is why it is so slow-growing. It needs good watering, especially in Spring and Summer, but also good drainage. If it has not been receiving supplemental watering during the very dry last two years, and now there has been rain, it may have feet standing in water beneath the surface of the soil, especially if you have clay soil.

We certainly would not recommend taking down a mature and apparently healthy tree just yet. Don't fertilize it. Often, that is a knee-jerk reaction when a plant does poorly, to fertilize. A plant under stress should never be fertilized, and with this tree, with the blooming already past for this season, you sure don't want to send a message to inspire new growth. Furthermore, this is a plant that really should never be fertilized, it is so well-adapted to its environment. Make sure it is getting plenty of deep watering, but that the water is draining. If water stands on the plant 30 minutes before it disappears into the soil, you have a heavy clay soil. Try mulching the root area, reducing the amount of water put on the roots each time, but increase the frequency. We would definitely give this tree another year or so, before it was eliminated from your landscape.

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