I have a tray planting of Pleioblastus pygmaeus (Sasa) miniature bamboo.

Actually, I believe the correct name is Arundinaria pygmaea. It is difficult to
pin down the taxonomy of this species, since it has never been known to bloom
in captivity.
I gave up on it already. First of all, examine it closely for spider mites, to
which it is very susceptible. You may also be having a problem with root rot or
other soil difficulties. Lastly, this is a hardy species, and may need winter
dormancy.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)