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Thursday - June 13, 2013

From: McKinney, TX
Region: Southwest
Topic: Diseases and Disorders, Trees
Title: Trouble with live oak in McKinney, TX
Answered by: Nan Hampton and Eric Beckers

QUESTION:

We moved into a suburban home with a live oak tree with a trunk diameter of about 50". I noticed recently how yellow the leaves look compared to the other live oak in the yard. There is not a pattern of yellow on the leaves, they are just almost uniformly yellow throughout each leaf and throughout the tree. Our soil contains a lot of clay. I believe the tree needs treatment with iron. My questions: does it sound like the tree needs iron, and if so, is there any way we as homeowners can treat the tree? Are there supplements available and would we have the tools to apply them?

ANSWER:

There are two oaks with the common name "live oak" that occur in Texas—Quercus virginiana (Coastal live oak) and Quercus fusiformis (Escarpment live oak). Neither occur naturally in Collin County but probably your live oak is Q. virginiana that was planted as a small landscape tree and, judging by its size, could be 100 years old—or maybe even more. According to the Smithsonian Marine Station at Fort Pierce, by 70 years of age Florida coastal live oaks can reach a diameter of 54 inches. However, I suspect your tree is rather more than 70 years old since it is growing in a cooler and less humid climate than the Florida coast. A venerable tree of this age certainly deserves special care. With that in mind I contacted Eric Beckers with the Texas Forest Service for his insight and advice.

He suggested that if you feel strongly that you have a soil deficiency of some sort, you should have the soil tested. Contact your Collin County AgriLife Extension Service office to learn how to get a soil test done.

One pest-related possibility he suggested was:

"After an initial springtime defoliation by a pest (often unnoticed by the landowner) a live oak's second flush of leaves will often look pale in comparison to it's neighbor that still supports an original crop of dark green, glossy leaves. Look for the multitude of half-chewed leaves and tender new growth and give them a few more weeks to mature and darken up."

Eric also pointed out that Quercus stellata (Post oak), a very common tree in Collin County, looks chlorotic (yellow) early in the season and gets its rich dark green color later in the summer.

Finally, it is not very effective for us to try to help you preserve such a valuable tree by trying to diagnose your problem from afar. We strongly recommend that you get an onsite inspection by a certified arborist to determine what treatment your tree might need.

From the Image Gallery

Coastal live oak
Quercus virginiana

Escarpment live oak
Quercus fusiformis

Post oak
Quercus stellata