Peter managed to contact me directly but I repeat my reply to him here for others to read too:
I was interested to hear about the South African bed in Sheffield Botanic Garden and would be most interested to hear in due course which plants survive well for you.
About Romulea tortuosa, I looked at the full dataset from our hardiness survey but it seems no-one had tried this species so I can offer no experience with it. Our survey showed that Romuleas in general did rather poorly. Romulea komsbergensis was one notable exception, with several people (including myself) finding as you have done that it is quite growable outside. The Komsberg area is one of the colder parts of South Africa so this is perhaps not surprising. One other that has been successful for me is Romulea sabulosa from the Bokkeveld Escarpment, another very cold area. Other plants from these colder areas would be worth sourcing and trying.
While pleased with the surprising cold hardiness of various bulbs as described in the article you mention, these results have been tempered for me this past winter as many of the plants proved irresistible to slugs and snails! And don’t mention the rabbits…..
Good luck with your plantings.
Paul
