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Wednesday - December 03, 2008

From: San Antonio, TX
Region: Southwest
Topic: Shade Tolerant
Title: Understory shrub for shady area in San Antonio
Answered by: Barbara Medford

QUESTION:

We would like to plant a small understory tree/shrub in an odd space that our new deck has created between our fence line and the house. A mature mountain laurel would be our dream but I think there is too much shade. Also since this would probably overhang the deck at some point, it might be kind of messy. Our next door neighbors' large red oaks branches extend over the fence and over our deck. This tree would be under their "umbrella". We would like this tree to reach about 10-12' high. What would you suggest?

ANSWER:

We'd like to start this by discussing that red oak hanging over the fence. There are a number of oaks referred to by the common name "red" oak, but we're assuming you probably have Texas native Quercus shumardii (Shumard's oak) in your neighbors' yard. Shumard's Oak dislikes the competition of understory plants, and, at maturity, will retard the growth of competing understory vegetation, apparently by allelopathic effects. Allelopathy involves the emitting of chemicals produced by the tree that will damage the growth of plant materials beneath it. Most oaks have this ability to some degree, with the Shumard's Oak being moderate in this respect. This, along with the shade involved, is the main reason it is difficult to grow grass or flowering plants beneath an oak. So, before you put a great deal of effort into planting a shrub there, you might consider that possibility. If your neighbor would be willing to do so, and certainly you have the right to ask that it be done, trimming of the tree overhang might help both with the shade and the allelopathy issues.

Now, on to the possibilities for this space.  You are correct that the Sophora secundiflora (Texas mountain-laurel) ordinarily needs more sun than it sounds like you have, and that all those flowers, followed by seeds, can make quite a mess. Moreover, the seeds, which grow in long pods, are bright red, attractive and very poisonous. Two of our other suggestions also have poisonous parts; you might consider the safety of having that kind of plant in an area where families and pets might gather. Follow the plant links to a complete webpage on each plant to learn other details of its growth and bloom. At the bottom of that page you will find a link to Google for more information on that plant.

EVERGREEN 

Ilex vomitoria (yaupon) - 12 to 25' high, bright red berries on female plants

Rhus virens (evergreen sumac) - 8 to 12' tall

DECIDUOUS

Amorpha fruticosa (desert false indigo) - 6 to 10'

Ilex decidua (possumhaw) -15 to 20' tall, clusters of persistent winter berries on female plants

Bauhinia lunarioides (Texasplume) - 6 to 12', fast-growing

Cercis canadensis var. texensis (Texas redbud) - 10 to 20'

Diospyros texana (Texas persimmon) - 12 to 36'

Prunus mexicana (Mexican plum) 15 to 35', like all members of Prunus genus has poisonous seeds

Ungnadia speciosa (Mexican buckeye) - 8 to 12', seeds poisonous


Sophora secundiflora

Ilex vomitoria

Rhus virens

Amorpha fruticosa

Ilex decidua

Bauhinia lunarioides

Cercis canadensis var. texensis

Diospyros texana

Prunus mexicana

Ungnadia speciosa

 

 

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