British Columbia: Saxifraga isn't rooted

I am new to growing Saxifraga, but have notice that my plants don't seem to be rooted into the soil. They just sit right on top, I can lift them right up, and they are still alive and blooming. Seems very odd to me. I planted them just like any other plant, with their roots in the soil about a year ago. Anyone know why?

 

Sounds like damage seen to coral root and primrose during summers here, when weevil larvae may be numerous enough to effectively shear the plants off near the soil line.