I find the Tristagma uniflorus cultivars much easier to grow, given hot-summer mediterranean treatment under glass here in the UK, than T. peregrinans Rolf Fiedler. The T. uniflorus cultivars, especially Alberto Castillo and random crosses with Alberto Castillo, multiply to flowering size very quickly and profusely. By contrast Rolf Fiedler for me is slow to increase (perhaps because of all those rice grains), though I think its vivid true blue outclasses all the others.
(I have retitled this thread to keep it in line with our genus (rather than species) topic-naming policy, and with current nomenclature. Thanks very much for starting it, Cali!)