The bloom stalk comes up in the middle of the fan and dies back quickly. The rhizome eventually dries up and dies also.
This is what bloom out means to me. It can happen to a single rhizome, or the clump.
Edited to add:
Wait a minute, maybe I read that wrong. I thought it was as described above, but the stalk(s) still produce their flowers, not die back quickly. Then the rhizome(s) dry up without producing any increase(s).
