Question
Hi Marc
I have a hillside area that no matter what I plant in it dies.  I have spent so much money and it still doesn't look good.  I'm pretty sure that it has to do with the irrigation.  Can you please recommend some plants I can use in the Los Angeles area that are drought tolerant for my hillside?  thanks

Answer
Hello, Nicki - I'm not so convinced it抯 the irrigation system.  Are there other undesirable plants/weeds on this slope?  A slope that is cut away from below the level of the original top soil is inert or infertile.  There are no beneficial microbes within topsoil that a plant needs for its root system. You might be trying to grow a plant on top of a barren rock.  If the slope surface is "friable" or loose, then these microbes will develop over time -- if not, you have a cliff face and no amount of water will help.

You can speed up the soil-creating process by adding a layer of fertile soil, or plant plants that need less care - In Southern California there is an abundance of slope-covering options, but only if the soil can sustain them, and it sounds like yours is struggling to do so.  

Below are some "tried & true" slope plants - so if you've tried any of these and failed, I'd have your soil checked for nutrients and fertility.

List is per LA County Dept. of Building & Safety.  More plant recommends can be found at http://www.parmeleegeology.com/PLANTS.HTM

Arctostaphylos uva-ursi (Kinnikinnick)
Baccharis pilularis (Dwarf coyote brush))
Cistus (Rock rose)
Cotoneaster, low-growing
Hedera (Ivy)
Hemerocallis (Daylily)
Juniperus horizontalis (Juniper, low-growing)
Lantana montevidensis (Lantana)
Lonicera (Honeysuckle)
Parthenocissus Quinquefolia (Virginia creeper)
Polygonum cuspidatum compactum (Fleece flower)
Pyracantha koidzumii Santa Cruz' (Santa Cruz Pyracantha)
Rosa species (Rose, low growing)
Rosmarinus Officinalis Prostratus' (Dwarf rosemary)
Vinca (Periwinkle)

Chose carefully if you live in a fire-prone area, as some are quite friendly to wildfires (Rosemary & juniper).

Ask at a local Garden Center for a recommended soils testing service; some will do it for a nominal fee ($20 or so).  All it takes is a coffee-bag sized sample, about 2 lbs of dirt, and will answer the question: will your slope sustain plant life?

Hope it helps  ~Marc