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Monday - March 21, 2011

From: Austin, TX
Region: Southwest
Topic: Shade Tolerant
Title: Deer resistant, drought and shade tolerant plants to go under oak tree in Austin
Answered by: Barbara Medford

QUESTION:

What is the best deer resistant, drought resistant native plant to grow under my huge Oak tree? Grass does not grow. Will iris bloom?

ANSWER:

Would you like whipped cream with that? Sorry, but when we get these designer plant questions, we wonder if there could possibly be anything else they could ask for. We will start with the problems involved in growing plants under oaks. Oh, while we're thinking about it - we found no iris native to Central Texas that would grow in the conditions described.

We don't blame you for wanting something colorful, but that is going to be a problem. Most colorfully blooming herbaceous plants and shrubs need a good quantity of sunlight to fuel their blooms. We consider full sun to be 6 or more hours of sun a day, part shade 2 to 6 hours of sun, and shade less than 2 hours of sun a day.There are other factors besides heavy shade that might be causing problems in getting plants to stay alive, including the fact that oak roots tend to be in the upper 12 inches of the soil, and form a mat that would be discouraging to other plant roots. In addition, there is the question of allelopathy. From the University of California Cooperative Extension article Landscape Notes by James Downer, Farm Advisor, we have extracted this paragraph about the allelopathy of oaks:

"Various studies have demonstrated that oaks can have allelopathic affects on surrounding plants. Allelopathy is the production of plant inhibiting chemicals by one plant to regulate the growth of others in its vicinity. One important group of chemicals produced by oaks is tannins. They are produced in leaves and litter and also directly by root systems in soil. Tannins are inhibitory to many organisms. Salicylic acid and other organic acids are also produced by oaks and are toxic to other plants. Allelopathy is species specific for the oak in question and the species that is inhibited."

In other words, it depends on which plant and which oak, and we don't have lists of plants that will grow under specific species of oak.

Now we'll talk about Deer Resistant plants, and see what of those are native to Central Texas, drought resistant (most plants native to Central Texas have to be) and go from there.We went to our Deer Resistant Plant List and selected on Texas, part shade to shade and dry soil to see what we could get. We selected only those that said their deer resistance was high. Follow each plant link to our page on that plant to find out bloom time and color, projected size and growing conditions.

Deer resistant plants that might grow under oaks in Austin:

Anisacanthus quadrifidus var. wrightii (Flame acanthus)

Asclepias tuberosa (Butterflyweed)

Melampodium leucanthum (Blackfoot daisy)

Monarda citriodora (Lemon beebalm)

Nolina texana (Texas sacahuista)

Salvia coccinea (Scarlet sage)

Salvia roemeriana (Cedar sage)

Tetraneuris scaposa (Four-nerve daisy)

From our Native Plant Image Gallery:


Anisacanthus quadrifidus var. wrightii


Asclepias tuberosa


Melampodium leucanthum


Monarda citriodora


Nolina texana


Salvia coccinea


Salvia roemeriana


Tetraneuris scaposa

 

 

 

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