I have two Phormium tenax (New Zealand Sword) plants, one in a heavy
claly soil and the other in a lighter sandy loam. Both were bought at
the same time, from the same place about eitght years ago. They are
both mature and stand approximately six feet high by six feet wide.
Location: Northern Scotland - other local phormiums are flowering just
now.

Problem:

Neither of these plants have ever flowered. Anyone have ideas about
why, please?

Cheers,
Compo.