Question
I live in the northeast and I need some recommendations on what to plant (hopefully seed) on a rather severe hillside slope that is subject to erosion.  The soil is a redish clay and very rocky and it is mostly shade.  I am on I light budget so I am hoping to be able to seed the area and cover it with hay, but I need a plant with a decent root sytem to hold the hillside in place.  I am hoping to get a recommendation on a non-flowering and very hearty plant that can hold my hillside (45 degree slope) in place.  I am hoping to seed, but if a vine or other type of potted plant is a better choice I will use it.  The soil gets very hard once the rain has compacted it down for awhile.  The top soil I tried to add just washed away with the first heavy rain.  Can you offer me any suggestions on what I should plant here to hold my hillside in place?

Answer
Mike,

If this was my troubled hillside to deal with, first, I'd put down some course jute landscape  netting. (Here's a link to a bad picture of what I'm talking about:
http://www.mrdrip.com/images/Fabric13b.jpg)
This is a groundcover of sorts, but it doesn't work alone. It's used inconjunction with planting, and mulch.  It  slows down erosion, stabilizing the surface of the hillside to allow your plants some time to get established.  It can help keep a good percentage of mulch(compost, not bark) in place also, which will help, then, with water retention.

Similar nets are available in plastic, but I don't do plastic. It can turn into a long-term hassle. The jute will slowly but surely be breaking down.

You probably can't get this a a normal retail gardening shop.    Head someplace that deals with the landscapers in the area.

Then, I wouldn't try to rely on one plant alone to do the work. I'd plant a combination of  hardy shrubs (Oregon Grape, red-twig dogwood, Viburnum davidii, Rosa rugosa).
I'd plant in staggered clumps, so that there was no "straight shot" down the hill for water run-off.  These would stabilize the hillside, provide
visual interest and eventually start either shading out some weeds again,or provide enough height difference that weeds wouldn't be so noticeable.

I'd also use a low maintenance grass/flower mix.  These are available at grass seed suppliers.  (for example, at  http://www.protimelawnseed.com/
look at their "environmental mixes").  They use a combination of low-growing grasses and wild flowers to provide an interesting cover that doesn't need to be mowed.

Until these get established, I'd watch what grows naturally.  I am usually pleasantly surprised by what shows up. Spot spray out only what is absolutely unacceptable (poisonous, thorny, etc).

For what it's worth,
Mark in Portland Oregon