I've looked through my seed-starting lists from the last 3 years a couple of times, but can't make the link to this plant shown below - obviously a Caryophyllaceae, I'd guess Gypsophila or maybe Cerastium? Anyone recognize it?
Those are not the greatest photos for IDs... I'll get some better ones. Thanks in advance.
My guess is a Cerastium alpinum or a close relative of that.
Indeed, very close! It turns out that it ought to be Cerastium latifolium, started in 2010 - I didn't go back far enough in my seed-starting notes. Funny that it took that long to bloom! Thank you very much for the great clue.