I don't think gardeners realize just how good Silene caroliniana ssp. wherryi is, a species native to portions of eastern USA. I have found it growing in mixed deciduous woods in fairly heavy shade. Yet as shade-tolerant Silene go, it is also low growing and floriferous. In the past I called it simply S. wherryi, but based on the Flora of North America, it is considered a subspecies of S. caroliniana, along with two other subspecies. See: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242417255
And it seems, that the plant as found in Massachusetts and New Hampshire, is properly Silene caroliniana subsp. pensylvanica :-\
I would check out my plant's identity, based on calyx pubescence, but after a long 7-8 year stint in the garden, it flowered itself to death the summer of 2006, leaving nothing behind, not even a seed :'( The last photo shown is its last hurrah.
Re: Silene caroliniana ssp. wherryi (Carolina Catchfly)
Sometime in April I'll know if mine came back. I've had it since 1996, and it's generally reproduced after its inevitable 'flowering itself to death' show after about 4 or 5 years in the garden. Obviously you can come by and get one or two if they did, in fact, survive this winter.
This is one I will have to watch for, being a shade plant; some of these eastern North American plants are hardier than I would expect..