In message , ChrisO
writes
I've got a Phormium tenax Atropurpurea, flowered for the first time
this year.
Now, in November, I'm left with these 9ft tall tubers in the middle
with the dead flowers on them.
Do these need to be pruned, or will it flower every year on the same
stalks ?


You can chop the stalks off if you wish - flowers are produced on new
stalks. Flowering is, however, somewhat sporadic.

--
Robert