On 7/20/2014 4:41 PM, Guv Bob wrote [in part]:
This is a small area - about 10 x 30 ft. Would be nice to have
grass there, but being dirt is OK, and not worth renting anything. A
few years ago I had to put ground cover on a bare compacted clay
hill. I ended up getting a 5/8-inch masonry bit and drilling 4-inch
holes about 6-8 inches apart, dropping red apple ice plant pieces in
and filling with good soil. Nearly all survived and within a year
the hill was covered.


While it used to be quite common to plant ice plant on a slope, the
recommendation today is very much against that. During a rain, ice
plant takes up much water and becomes quite heavy. The roots tend to be
shallow and not very extensive. The result is that the ice plant will
often pull loose, slide down the hill, and take part of the hill with it.

I am very sensitive about proper planting of slopes since the hill in my
back yard has slipped twice. The second time, the repair cost almost
four times what I paid for my house; my grandchildren will make the last
payment on the federal disaster loan. No, there is no such thing as
insurance against a slope failing; and the repairs are never guaranteed.

Grape vines are very good on a hill; they have very tough, deep roots
and generally do not care how poor is the soil. Alone, African daisies
or ivy (English or Algerian) are not good because their roots tend to
form a mat that can become a weak layer; African daisies and ivy mixed
together, however, are excellent on a hill because those mats are at
different depths and tend to be less concentrated.

According to the grading experts in my county's public works agency,
trees on a hill can be bad. In a wind, they rock back and forth,
breaking up the soil around the bases of the trunks. With a major rain
storm, that becomes a path for a large amount of water to funnel down to
the subsoil. Depending on their alignment, this can lubricate the
boundary between soil and subsoil and trigger a slide. On the other
hand, shrubs are okay.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary