At the edge of a concrete walkway I have a couple of hardy geraniums planted that I'm liking the looks of because of their low, mounding habit (less than 6 inches tall). Cultivar name is 'Biokovo.' It's blooming now and appears pest-free so far in my limited experience (2 years), with flowers in the blue/purple range. I also have G. 'Rozanne' and find it tends to grow quite a bit larger and encroach on the space of other nearby perennials whereas I haven't seen that tendency in 'Biokovo.' 'Biokovo' was still blooming late last season so I would say based on its performance in my part-sun garden, it's long-blooming + low-maintenance since I planted two and have done nothing to either one subsequent to planting them. Both returned again this growing season and are looking robust. My soil is sandy loam, gets no supplemental water or fertilizer. Bottom line: I'm well pleased with this perennial.

I have PLENTY of both regular and variegated kerria japonica if you want some suckers, also clerodendrum trichotoma (harlequin glorybower -- a nice five-foot shrub that blooms in white fragrant flat panicles, then the berries turn blue while the brachts stay maroon, and then later the leaves go golden before they drop -- definitely a three-season shrub, though again it DOES sucker). I also have a large abelia (really a part-sun shrub, but truly blooms all summer) that I would like to dig up and replace with a blueberry. I live in Lanham, near NASA -- is that close enough for you? LynnT

Epimediums are an excellent suggestion. Lithodora will not take either shade or wet. Hellebores are evergreen and shade tolerant and they flower in late winter. There's a dwarf species of Gaultheria that stays much shorter than salal does. Oregon wintergreen I think it's called. I see it up in the Olympics so it's not restricted to Oregon. Very nice evergreen native groundcover. Also look for twinflower, another native evergreen groundcover.

Partridgeberry is a lovely ground cover and a good protection for spring ephemerals. Labrador violets have pretty purple tinged leaves. I have a pretty variegated leaf wood phlox called Montrose Tricolor which until recently was the only wood phlox the slugs did not destroy. Pixie