Native Plants

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Thursday - April 14, 2011

From: Soquel, CA
Region: California
Topic: Erosion Control
Title: Solution for erosion on steep slope in California
Answered by: Nan Hampton

QUESTION:

Dear Mr.Smarty Plants, I have a serious hillside problem in Santa Cruz County resulting from the recent deluge of rain. Steep to sheer now with no plants left on it after the hill slide washed to the road. It was a rather wild hill side before it slid. Poison oak, pampas grass and scotch broom. My concern is to now to stabilize the hillside and prevent further loss of my property which has been taken away in truckloads. I read about your native grasses that reach down up to 15 feet. Which ones do you recommend? I would like to go with natives since it is a large mostly wild area now mud and sandy. Much appreciation for any input you can give me to help solve my problem. Thank you.

ANSWER:

California has been getting an unusually large amount of rain this spring and it sounds as if you got more than your share. I don't think that we are going to be able offer plants alone to stabilize your slope since it sounds as if it was already covered with plants when your hill slid to the road. You may need to consider a retaining wall or a series of terraced retaining walls to stabilize the slope. Las Pilitas Nursery (in Escondido and Santa Margarita) has a useful article, "Simple erosion control for a hillside or garden slope," with advice on solving the problem using native plants and mulches as well as, possibly, retaining walls. We don't agree completely with their suggestions for plants since they are a bit negative about using grasses. A monoculture of grasses alone is probably not the best solution but including some native grasses is an excellent choice for controlling erosion because they develop extensive fibrous root systems that hold the soil in place. In combination with native woody and herbaceous perennial native plants, they would be very effective. Since I don't know the dimensions of your slope, I can't tell you whether it is feasible for you to construct a retaining wall (or walls) yourself. It is possible that you may need to find a landscape specialist to help you. You can find landscape professionals specializing in native plants for your area by searching in our National Suppliers Directory.

Another possibility is to use erosion-control blankets along with terraced retaining walls to stabilize the erosion area so that seeds have a better chance to germinate and become established. The erosion-control fabric works by slowing the runoff water and allowing sediment to fall out rather than be washed away. Seeds are sown under the erosion-control material and grow up through the matting when they germinate. Underneath the matting the roots of the plants growing through the erosion-control material anchor the soil to stop the erosion. If you use erosion-control blankets made of biodegradable material, they will eventually disappear leaving the plants to control the problem. Seeds can be sown under an erosion control blanket or grass plugs and other plants can be planted by cutting holes through the blanket. This material is available at most nurseries.

Here are some plants native to Santa Cruz County that would be useful in stabilizing your slope. You will need to check the GROWING CONDITIONS section for each to see that they match those of your site for sun, soil type and moisture.

Artemisia californica (Coastal sagebrush)

Arctostaphylos glandulosa (Eastwood's manzanita)

Arctostaphylos hookeri (Hooker's manzanita)

Dendromecon rigida (Tree poppy)

Eriogonum fasciculatum (Eastern mojave buckwheat)

Festuca californica (California fescue)

Hordeum jubatum (Foxtail barley)

Koeleria macrantha (Prairie junegrass)

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