25 May Diseases and Disorders, Trees

From: Boerne, TX
Region: Southwest
Topic: Diseases and Disorders, Trees
Title: Young Mexican White Oak Losing Leaves in Texas
Answered by: Anne Van Nest 

QUESTION:

I have a 5 yr old Mexican white oak, 20 ft tall losing its leaves mostly at the top. They turn brown & fall off. It does not lose its leaves in the winter, right?. About 3 ft from the top down is bare, The root flanges are not showing at the base. Could the dirt be piled too high around the trunk? I am letting my hose slowly drip in case it is just too dry. What do you think? Do I have a problem? 

ANSWER:

Mexican White Oak (Quercus polymorpha), according to the Texas A&M Forest Service says that this tree is only recently discovered in the U.S. (1992) as a native tree species, but widely available in commercial nurseries. Naturally occurring only in one known U.S. population, near the Devil’s River in Val Verde county, but more common in Mexico. Now planted widely as a landscape tree.

The leaves are simple, alternate, 2″ to 5″ long, highly variable, but often with several shallow lobes or teeth towards the tip. Leaves are thick, leathery, and semi-evergreen, with distinct raised veins on the yellowish underside. New leaves in spring are peach-colored and in colder climates the leaves are late-deciduous and turn yellow-brown.