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Tuesday - May 18, 2010

From: San Antonio, TX
Region: Southwest
Topic: Propagation
Title: Problems with Shumard oak in San Antonio
Answered by: Barbara Medford

QUESTION:

Hello. I live in San Antonio and Have a question about a Shumard Red Oak. It's growing at an average pace, seems a little more vigorous this year. It's a nice tree with great fall colors. HOWEVER, when winter comes around the leaves that are supposed to drop never do until Mid February. It looks like the tree is dead in December through February but the leaves are firmly on the tree. When one is removed you see sap. Again, it keeps the brown leaves until February, Drops the leaves and within two weeks begins budding - with twice the amount of foliage. I notice another tree down the street from me does the same. Is this normal? I have three Texas red oaks that don't do this.

ANSWER:

We understand that there is some confusion about the classification of the Quercus shumardii (Shumard's oak), in that it is sometimes another species of the genus Quercus sold as a Shumard Oak, a hybrid or just mistaken identification. What you are seeing is ordinarily what a live oak would do, except that the live oaks' leaves usually remain green until they drop, all at once, in early Spring.

From our Native Plant Database webpage on the Shumard Oak:

"Shumard oak is what can only be called a botanists species, usually unrecognized by lumberman and layman, but an object of triumphant discovery to the botanical fraternity."

This USDA Plant Profile shows the Shumard Oak as being native to near Bexar County. We think this may be a problem of mistaken identity. Very broadly speaking, an acorn of this tree gathered from east of I-35 needs acidic soil to thrive. An acorn from west of I-35 needs alkaline soil. One writer even recommended that you know whether the seed for a Shumard Oak was gathered from acidic or alkaline soil. If it was gathered from acid soil but grown in alkaline soil, it would tend to be chlorotic with pale and/or discolored leaves.

So, the plot thickens. This tree very easily hybridizes with other oak species, mostly native to acidic soils, such as East Texas. These trees include Quercus palustris (pin oak), Quercus falcata (southern red oak), Quercus phellos (willow oak), Quercus nigra (water oak) and Quercus marilandica (blackjack oak). And where does San Antonio sit? Right on top of I-35, so this is definitely a tree with a confused background. The Shumard Oak is considered a red oak, and is susceptible to Oak Wilt. When you look at the leaves and the growth habit of the trees this one likes to pair up with, it is no surprise that the tree you have does not act like you would expect it to.

Many tree retailers sell plants they have taken from wholesalers, and have no idea of the origin or even the true name of the tree. "Shumard Oak" could just as easily be a trade name, attractive to buyers, as a true species name. We can't see that it makes a whole lot of difference at this point. If your tree is growing well and doing what you want it to do, we would suggest you not worry about exactly what part of its mixed parentage has contributed that late deciduousness of the Shumard. We are going to try to find you close-up pictures of the leaves from each of these trees.

Quercus palustris (pin oak) - pictures from Google

Quercus nigra (water oak) - pictures from Google

From our Native Plant Image Gallery:

Quercus shumardii

Quercus falcata

Quercus phellos