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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Thursday - April 25, 2013

From: Columbia, SC
Region: Southeast
Topic: Soils, Erosion Control, Grasses or Grass-like, Shrubs
Title: Erosion control on slope from Columbia SC
Answered by: Barbara Medford

QUESTION:

We are in the process of having a new home built in Columbia South Carolina. Part of the front yard has a steep slope starting approximately four feet from the corner of the house and running to the street. We are concerned about possible soil erosion. The soil is red clay, and the area will likely have full sun exposure. It is right in front of the house, so we don't want anything that grows too tall. What types of plants would you recommend in this area to prevent soil erosion?

ANSWER:

The most important thing is to choose plants native to your area. The Lady Bird Johnson Wildflower Center is committed to the growth, propagation and protection of plants native not only to North America but to areas in which those plants grow naturally; in your case, Richland Co., South Carolina. Since you know your soils are clay, selecting for plants that grow in soils native to your area will make for an easier choice. Erosion is always a concern on a slope and clay soils add the complication that clay is composed of very fine particles that hold moisture and swell, threatening roots with drowning. We find that grasses, with their long fibrous roots, are best suited for erosion conditions. Also, we can look for some low shrubs, heights 1 to 3 ft. for more coverage.

To make selections for your purpose, we will go first to our Native Plant Database. Using the Combination Search, about midway down the page, we will select on the drop-down menus: South Carolina for State, "grass or grasslike" for Habit (for the first round search), "sun" for Light Requirements and 1 to 3 ft. tall for Height. Our second search was for "shrub" as the habit.  We did try to check to see if each plant we chose was native to your area, but apparently South Carolina has not supplied that information for many plants to the USDA for their Plant Profile Maps. So, we will read the soil descriptions for each plant to make sure each is tolerant of clay soils. However, we did not find many of those either; two grasses and four shrubs. Two of those shrubs grow to 3 to 6 ft. tall.

We are wondering, since your house is under construction, if you might be able to have your clay soils amended by tilling in some sand, decomposed granite or, best of all, good quality compost. Making these changes is going to make many more plants accessible for your landscaping. Then you could revisit our database and have more choices. Read this article from the National Gardening Association on Improving Clay Soils. For more information on soil testing, contact the Clemson University Extension Office for Richland County.

Grasses and shrubs for Central South Carolina:

Aristida purpurea (Purple threeawn)

Poa arachnifera (Texas bluegrass)

Verbena halei (Slender verbena)

Borrichia frutescens (Bushy seaside tansy)

Clethra alnifolia (Coastal sweet pepperbush)

Hibiscus laevis (Halberdleaf rosemallow)

 

From the Image Gallery


Purple threeawn
Aristida purpurea

Texas bluegrass
Poa arachnifera

Texas vervain
Verbena halei

Bushy seaside tansy
Borrichia frutescens

Coastal pepperbush
Clethra alnifolia

Halberdleaf rosemallow
Hibiscus laevis

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