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Wednesday - August 26, 2009

From: Houston, TX
Region: Southwest
Topic: Shade Tolerant
Title: Colorful native plants for oak tree shade in Houston
Answered by: Barbara Medford

QUESTION:

I live in Houston Tx - our subdivision entrance has many oak trees. We cannot find anything that will "stay alive" around these trees. It is mostly shady, but gets a slight bit of sunlight. we would like something colorful. Please make some suggestions.

ANSWER:

We're assuming you are referring to an entrance to the whole subdivision, rather than in an individual yard. We are also assuming that some arrangements have been made for irrigation of the area. 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."

Now, having told you all the reasons why things won't grow there, we will go to our Native Plant Database, and look for plants native to the Harris County area that can tolerate part shade or shade and have some landscape value. We went to our Recommended Species section, clicked on East Texas on the map, and selected first on herbs (herbaceous blooming plants) and next on shrubs under Habit, and part shade and shade on Light Requirements. We found 5 blooming plants and 3 shrubs that might work for you. Remember, you are not going to have year-round color, nor even green. Some of the plants are evergreen, some are deciduous and at least one shrub has winter berry color. Follow each plant link to our webpage on that individual plant to learn more about its characteristics and propagation.

Herbaceous blooming plants for oak tree area in Houston:

Callirhoe involucrata (purple poppymallow) - perennial spreading evergreen, blooms white, pink or purple March to June, sun or part shade

Coreopsis lanceolata (lanceleaf tickseed) - perennial evergreen, 1 to 2 ft. tall, blooms yellow April to June, sun, part shade or shade

Lobelia cardinalis (cardinalflower) - perennial, 1 to 6 ft. tall, deciduous, blooms red May to October, sun, part shade or shade

Phlox divaricata (wild blue phlox) - perennial evergreen, 8 to 18 inches high, blooms white, red, pink or purple March to May, part shade or shade

Salvia coccinea (blood sage) -annual or perennial, blooms white, red or pink March to October, sun, part shade or shade

Shrubs for oak tree area in Houston:

Callicarpa americana (American beautyberry) - 3 to 5 ft. tall, deciduous, blooms white, pink May to July, part shade

Malvaviscus arboreus var. drummondii (wax mallow) - perennial, deciduous, 3 to 6 ft. tall, blooms red May to November

Symphoricarpos orbiculatus (coralberry) - 4 to 6 ft. tall, deciduous, blooms white, green April to July, part shade or shade


Callirhoe involucrata

Coreopsis lanceolata

Lobelia cardinalis

Phlox divaricata

Salvia coccinea

Callicarpa americana

Malvaviscus arboreus var. drummondii

Symphoricarpos orbiculatus

 

 

 

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