Your bleeding hearts are lovely. My mother has a similar slope and her ground cover is lamium. Hers has white blooms, I believe it is available in other colors as well. It thrives in shade, even dry shade on her slope, and yet it doesn't muscle or crowd out other plants. You could also add hostas. They aren't technically a ground cover, but they do cover a lot of ground once they are mature, and they will probably love the site since your bleeding hearts and ferns look happy there.

Thank you all so much for your detailed replies! Sorry it took me a bit to get back to everyone. gardengal48~I am indeed in CA--East Bay, with a desert-like micro climate but since we have in-ground sprinklers to keep the yard green, the spot I'm looking at stays pretty moist (since there's no sun to evaporate moisture). The spot is between the front yard and house, and is about 10-15ft wide by 4-6ft deep (I haven't measured yet, and don't think this would be considered "large"). I've looked up a few of the plants that have been suggested, and I like the idea of a low growing ground cover like the vinca minor, but want to avoid anything that is invasive and requires more than minor maintenance. I think what I'll do is make a list of what I like from the suggestions, and take it to a nursery to see what they offer for this area, and see if there is something I can plant in the next few months. I think it's good to have a list to go off of instead of walking in there and having to go with what they suggest (done that, didn't like the results).

I am a consulting horticulturist and I deal with horsetails constantly. Pulling does NOT compound the problem as long as you keep at. I have horsetails in my own inherited garden and that is how I deal with them and fairly successfully as well, I might add. The roots run quite deeply and pulling does not remove all the roots. New growth can emerge from these but if you keep pulling ALL the new growth before it develops much height (less than 8"), the plant is unable to photosynthesize and will eventually weaken to the point where it will not return. And only a few of the plants produce spores and only in early spring - they are very distinctive compared to the typical horsetail - and these should be pulled as soon as they appear so the spores do not develop. Most of the horsetails' spread can be attributed to the rhizomes, not the spores. I do this for a living and this is a very accepted and relatively efficient way of dealing with these pests. The lime will have NO effect so save your money and your effort. Horsetails can and do grow in a lightly alkaline soil. Increasing the pH any more than that would make the soil inhospitable to most anything else as well. Any low growing or spreading perennial that shares similar growing conditions will serve to protect the clematis roots. I like hardy geraniums. But unless the horsetails are eradicated first, you will be dealing with these weeds indefinitely. And attempting to remove horsetails from within the root system of an established clematis plant is asking for unnecessary trouble.

lala is correct...your plant blooms on old wood, so the flower buds for this season were actually set last summer...so you cut the plant to the ground, you cut all the flower buds off from last yr...now that the plant is growing back, very often, the re-growth plants are quite vigorous...if you want blooms next yr, and prove your neighbor is wrong, do not prune for the yr, and no spring pruning next yr, no way, no how...then offer good winter protection for the bare sticks (this forum has a lot of topic threads on the subject)...feed the plant nicely next spring..and wait for the big blooms to welcome you..good luck.