Answer: There are a number of plants, both upright shrubs and trailing groundcover type perennials, which can help control erosion on your slope. Ground cover plants, ranging from the traditional evergreen, blue-flowered periwinkle or vinca minor (kept in bounds by a periodic edging with a shovel) to some of the easy perennials such as creeping phlox (Phlox subulata) or Black-eyed Susans (Rudbeckia) or perhaps daylilies (Hemerocallis) or a creeping form of sedum are possibilities. Blue Rug juniper is popular in your region, as is the shrubby Ceanothus (California Lilac). In all cases, however, they will establish faster and grow better with less maintenance if you take care to prepare the soil first before you plant by working in plenty of organic matter. In addition, a few inches of organic mulch placed around the plants will help keep down weeds, reduce erosion and help maintian a more even soil temperature and moisture level while they are establishing themselves.
For even more ideas, visit the following website: http://www.laspilitas.com/garden/howto/slope.html
Good luck with your project!
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