This was one of the last photos I took of any plant in my Pennsylvania garden, before moving to Texas. Looks to be in caryophyllaceae, but it doesn't match any of the plants I had on record as growing in my rock garden - it may have been grown from mislabeled seed. I had various dianthus and saponarias in that general area. Seed almost certainly came from NARGS exchange, since that's where the bulk of my rock garden plants came from. Any ideas?