General advice for planting on steep slopes is to plant the smallest sizes feasible, and plant at the best season to get them established so that they won't dry out. Assuming that holes can be dug to plant one gallon or 4 inch size containers, the black nursery can can be cut down one side with the bottom removed, and used on the downslope side to hold water in place until the plant is established.

If you don't typically get enough regular rainfall to keep new plants alive on a steep slope like this, then you may need to provide temporary drip irrigation line for the first summer. Adding jute erosion control netting to the slope might also allow you to add a bit of top soil and hold it in place, which might also give more flexibility in getting new plants established.

I'd think that plants like Cotoneaster and smaller junipers, and possibly Arctostaphylos uva ursi might be logical plant choices.

"Assuming that holes can be dug to plant one gallon or 4 inch size containers, the black nursery can can be cut down one side with the bottom removed, and used on the downslope side to hold water in place until the plant is established."

Wow--this is a very helpful idea! Questions: What happens with the nursery pot over time? Is there a way/a plan to extract it over time? Would you try this technique with biodegradable pots or would they degrade too quickly? Any recommendations?

That slope is not that steep that the traditional approach mentioned of a planting shelf can not be used. It would be helpful to have a plant that can take some burying of the crown or that can re-root easily like a shrubby dogwood. The upside of a planting shelf may be rather steep and erosion happens, which will wash in some soil.

If you are using plants that root as they grow, or can take some soil over the stems without rotting out, the shelf method may work for you without creating an artificial rim. I like using the plastic nursery can on really steep slopes because it holds up better than a berm, and if you're using densely growing ground cover type plants such as Juniperus confertus or Cotoneaster dammeri, it won't show after a few months of growth, and can simply be left in place or removed by pulling out later.

It did look like at least a portion of the slope was too steep to easily create plant shelfs, and that sloughing off of soil would be an ongoing problem, and there are many plants that can't tolerate soil covering them from above.

Good ideas bahia. I bet as some plants start to grow out, some landscape staples on stems will help speed things up for plants that root along stems.

I am also trying to think of some other 6-8" plastic material that is flexible to be a temporary shelf retainer other than pots. And possibly lend itself to a larger shelf

If you want to mix in some low things I really love lamb's ears. It looks very nice paired with burgundy. Some ornamental grasses would look nice, too. They come in so many different heights. One of the cascading ones (I think it's fountain grass) would look lovely on the hill.