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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Tuesday - August 16, 2011

From: Brenham, TX
Region: Southwest
Topic: Diseases and Disorders, Pests, Watering, Trees
Title: Oak tree with browning leaves in Brenham TX
Answered by: Barbara Medford

QUESTION:

I have a large oak tree in my small back yard. I also have a sprinkler so the tree has been receiving some water. Nevertheless, some of the leaves are turning brown in patches. Would drip watering over days help this situation due to the drought?

ANSWER:

This year, everything is turning brown, some in places like your oak tree, and some all over, indicating a very dead plant. There are all kinds of diseases and pests of trees or, more specifically, of the oak that could be causing this. Here is a paper from Forest Health Protection, Southern Region on Oak Pests. Since we are neither entomologists nor plant pathologists we cannot diagnose the specific problem, especially without seeing it.

But, because of the extreme weather in Central Texas, we are betting on the heat and drought being the source of the problem. Before you even try to find out if insects or disease are causing the browning, we would definitely recommend watering more. Remember how far out from the trunk those roots are growing-at least as far out as the drip or shade line, and usually two to three times that. Drip watering of a tree is really only effective when the tree is very small and newly planted. In that situation, we suggest you push a hose down in the soil and let the water drip slowly until water rises to the surface, at least twice a week during hot, dry weather. For a large mature tree, you need to get water farther out and you probably couldn't get a hose in the ground for drip watering there. Use the sprinkler, moving it around to water each area where roots probably are, and leave it in each position long enough to really wet the soil. Again, twice a week.

The leaves that are brown will not turn green again, it will soon be time for the oak to drop leaves anyway. But if you start providing water to the little rootlets all up and down the length of the main roots, the tree will have the energy to put new leaves on in the Spring season.

 

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