Thanks to Rupert and Sacha. I may try B&T.

Incidentally, the common one in the UK is I. tricolor, which is fairly
easy to distinguish from the I. nil complex (including purpurea, nil,
hederacea and indica). It has glabrous stems, where the others are
hairy, and its sepals are different. I have no idea why it should
get so badly confused.

The common ones in the USA are purpurea and hederacea, just to confuse
the issue. And I suspect that they are also more common around the
Mediterranean.

The 'purpurea' seed that I tried was definitely mostly tricolor. The
"Scarlett O'Hara" was one of the I. nil complex and scarlet but was
NOT what it said it was, and was a miserable plant! This might have
been because it WAS nil (nearly as tropical as indica), and there was
a typical mediocre summer.


Regards,
Nick Maclaren.