Someone recently mentioned the observation of feral black irises growing
in the southwest. I mentioned this to the local Iris breeder when I met
him on the allotment site this morning, and his immediate reaction was
that they would be Iris chrysographes Black Form.

I also noticed black water iris (Louisiana iris) for sale in a local
garden centre a few days back. Said Iris breeder says that these don't
persist in Britain.
--
Stewart Robert Hinsley