I grow two species here, about 35 miles west of Minneapolis:
D. nubigenum
D. basuticum
I have a couple others, but can't say if they are truly hardy here yet.

Grow thim in extremely lean soil, nearly all mineral, or they will grow very quickly and not flower much if at all. They are very susceptible to winter wet. I prefer basuticum as it has yellow flowers with white centers, is more compact, and is more floriferous.

Thanks, I really like thier foliage too. I have one dry area that I thought it might make decent ground cover, hopefully the winter wet won't affect it like a number of other spots in my yard.
Any suggestions for a low ground cover that can take the winter wet? it has full sun, heavy clay that I have been ammending for 4 years but it might need another 4 before it lightens up.

Don't expect any delosperma to keep weeds out. Just an FYI.

For your moister sunny area, there are several good selections of Phlox stolonifera (for instance - Homefires), or even the straight species would do nice. Something different that most people don't have. I am assuming you want something less than 6 inches. The phlox will have flower stalks of 8 inchs though. Any ajuga will do fine, but may get out of hand.