Is it in sun or shade? You need to find ground covers. If sun, you might try creeping phlox or the really low types of sedum, or perhaps ajuga, ivy, or vinca minor. If shade, lamium would be an option, or sweet woodruff. Whatever you plant, I'd still recommend working in some good compost or manure -- your plants will take off quicker with some amendments.

I live with the same situation -- planting on that hillside is so darned hard!

I am facing a similar situation in having a hillside that is covered with turf. The grass has been so hard to mow on the steep hillside, I really am seeking out something to grow there. Also have loads of clay here too and not a big fan of ivy.

I like the idea of sedums and I would suggest some low growing conifers like creeping juniper. Not sure how steep your hillside is, but I've been thinking when money allows for terracing out my hillside slope so I can manage watering and planting easier. I've planted some Daylily here last fall and they're starting to come up, the hope was they'd naturalize the area.

Good luck!!!
Shannon

Daylilies do well on sunny hillsides; less well in partial shade. Hostas could also do well on a hillside, and seem to tolerate the clay well. We have a hillside planted with creeping junipers ("blue rugs"). It has two problems: competition with tree roots has killed some of them, and the landscaper who put them in used a formula for how close together to put them -- turns out not to have been close enough -- they grow downhill, but don't spread from side to side. So if you get them, spring for more rather than fewer. We're constantly having to mulch and weed between them, which is not fun on the hillside. (oh, yeah, weeds manage to grow through them as well!) Ours haven't really thrived -- not sure how much is due to the clay soil, and how much to the competition from trees. We mulch and add compost every year, and water in the heat of summer, so they've had some TLC.

I must say, my favorite hillside planting is the phlox -- it's a thick mat that doesn't allow for weeds, and it's so gorgeous when it blooms. Second to that is the sedum rupestre -- interesting bluish foliage with yellow flowers in early summer, shallow-rooted (so it just doesn't care about clay!) and has several times survived being run over by workmen's trucks -- you'd never know the next day!