PlantFiles: Leibnitzia
Leibnitzia anandria

I'd just like to add what I know to your "unknown" points: - the rosettes are about 8 cm wide, so spacing is about that.- they are hardy in our Zone of 5, but I would say much lower, since I'm on a windy rooftop!-Flowers are supposed to be white in the spring, and then late summer/fall bloom opens directly to beige seed heads--I've never had spring bloom yet, and mine is 4 yrs old!- The leaves are serrated and ground hugging rosettes. - Easy to grow from seed, which is collected from the fluffy seed heads when they open fully.
My plant is in scree, so it does well in dry conditions, although that makes me wonder if it would make spring flowers in moister conditions. I am going to grow some for next spring and will try that.