I'm surprised you lost the crown vetch. In my area, this is a pretty invasive plant and pretty tough to kill. Then again, I, too have tried to get a bank of them going, and they seem to grow everywhere BUT where I want them to. That being said, these are a pretty tough plant with roots that really run and will take over an area fairly quickly. I think the key to your problem is the acidic soil. The hill area you describe is pretty big..otherwise I'd suggest trying some rhododendrons and azaleas. The wind might be pretty tough on them though. How about pachysandra as a ground cover??? I intensely dislike this plant, since it IS an incredibly prolific groundcover that will virtually choke out anything else in it's path. So, if you want it, know that you will also not grow anything else there. It MAY well be what you're looking for. It is truly an indestructible plant - actually a nice looking, non-blooming, green groundcover that puts out lateral roots like there's no tomorrow. Hope this suggestion helps. You could probably do it yourself..just get a good number of plants, space them out, and it probably won't take that long until they take root and take off.

Best,
Keith

Thanks for the response, Keith! I've been told that my hill is too sunny for pachysandra which is too bad because a bunch of people have offered to let me poach from their own beds. I've decided not to repeat the hydroseed even at a bargain price. Since the guy isn't a horticulturist I think I'd be sending good money after bad.

Chris

Too sunny........really? My mom has pachysandra all over her beds in full sun for the most part. I think it'd be worth a try. It is a pretty tough (read: virtually indestructible) plant in my opinion. How about creeping sedum???? That'll take full sun.

Don't don't do the crown vetch...after a couple of years there is a lot of dead stuff in the planting that not only is an ugly mess but also a fire hazard. The state of Iowa at one time seeded lots of highway banks with crownvetch....and after lots of fires they are getting rid of it.
How about that old stand by day lily?
The pachysandra will stand full sun if it gets lots of water...but that is not likely on a steep slope.
Linda C

Thanks for the heads-up on daylilly, Linda! I'm checking it out and it looks like it could be a major part of my answer. According to classygroundcovers.com it is good for erosion control, likes full sun, tolerates bad soil and is hardy to zone 3.

BTW - googling daylily brought me to the classygroundcovers.com website. Their category search is a great way to zero in on groundcovers to address various circumstances.