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Tuesday - September 27, 2011

From: Houston, TX
Region: Southwest
Topic: Watering, Trees
Title: New growth on live oaks in Houston
Answered by: Barbara Medford

QUESTION:

My 2 10yr. old live oaks are putting out new growth (branches?) although, here in Houston, TX we are having such a drought. For the last 3 months, I have conscientiously watered my entire yard via sprinkler system every day, faithfully, to insure a green yard. Although last few wks, of course, I've had to resort to water rationing only 2 days wkly. Even now, each area of yard is watered 30 min/2 times wkly. Are the lives oaks putting out new growth due to stress, or has my daily watering done any good?

ANSWER:

By coincidence, we just answered a question on over-watering. Although it involved a different plant, we suggest you read this previous question. If you have natives to your area, which is what the Wildflower Center is all about, you have been overwatering them. We are thinking in the Houston area you probably have Quercus virginiana (Coastal live oak); this USDA Plant Profile map backs up that belief.

Our answer to your question kind of depends on where the new growth is appearing. If you are getting sprouts from the ground, these are sprouts from the roots of the tree. This is a common habit of live oaks, and yes, it is often a sign of stress in the parent plant. As the tree is having difficulty supporting itself in heat and drought, it sends out sprouts from the roots, which are protected in the soil, and are the storehouse for nutrition and water for the whole tree. These sprouts are basically new "branches," creating new leaves, which are the factories for food for the tree. Then, if the upper part of the tree begins to die from the environmental factors (which can also include wounds to the tree by equipment) those tiny branches from the roots will help to sustain the tree and provide it with sustenance to regrow. These sprouts are not desirable, as some of them will survive and grow larger, forming a "motte" of small trees. This is often seen in the wild, but is too large for residential gardens. Worse, those multiple intertwining roots can be a conduit for the dreaded Oak Wilt from one tree to another.

If the branches you are asking about come from the existing upper branches and trunk of the tree, that is probably just what they are-new branches. They are usually light gray and thin. As the live oak grows it is good to pay careful attention to pruning to eliminate weak crotches in new branches to strengthen the whole tree. Remember no pruning except from about November 15 to January 15, when the Oak Wilt fungus-carrying nitiludid beetle is dormant. Pruning of any branch larger around than your thumb should be followed by painting with wound paint.

From the Image Gallery

Coastal live oak
Quercus virginiana