Thanks for the advice. I saw your web page while looking up those
ferns. I live in Rhode Island (Zone 6?) Will they work here? Also, any
particular kind of cranesbill? My "Johnson's Blue" is not doing too
well there--floppy and not too many blooms.

Epimediums would do fine amidst the maple roots.

Crane's-bills would do well unless you failed to get water to them; the
maple roots can suck them dry otherwise, but wtth sufficient water the
crane's-bills quite naturally grow up near the bases the trees & shrubs.

Hardy cyclamens are adapted for life in just the conditions you outline.
But they come & go seasonally; for more of an evergreen presence, asarum
wild gingers should do great.

For something BIG that should do well, Wallich's Wood Fern or Western
Sword Fern could be very impressive in such a spot.

-paghat the ratgirl