Sisyrinchium striatum

Very pretty flowers, but always the base blackens and the plant dies off for me over the winter.

That is normal for the Iridaceae isn't it? Each fan is monocarpic.

Yes, but there's never any replacement pieces. At least a bearded Iris shrivels over a couple of years, leaving replacement offspring.

Ah, so it just generally struggles then? How odd.

They multiply quite rapidly don't they.