Learned a lot from Tim Tuttle's Petrocosmea talk... For the 2009 flower show, class 36 (the non-flowering Pets) had so many entries that it needed to be split into 6 sub-classes. That's remarkable when you consider 12-15 years ago there were few species in cultivation. The only hybrid for years was 'Momo' (P. nervosa x P. flaccida).
At one time, Petrocosmea was considered very difficult to hybridize. Tim attempted hybridization for several years without success. Then he discovered that keeping the plants cool and inside domes for extra humidity produced better flowering and pollen. His cross of P. sericea x P rosettifolia has resulted in a couple of promising hybrids: 'Rosemary Platz' (whose namesake was at the convention and luckily I had a chance to chat with her) and 'Keystones Bantam'. Both have retained the interesting leaf veining of rosettifolia. 'Keystones Bantam' is very petite, as its name suggests.
I am very pleased that leaves of 'Rosemary Platz' that I had put down in March are producing plantlets finally. Tim has suggested that leaf cuttings need little light, cool temperatures, humidity, an open mix and sparse watering. This avoids leaf rot.
Other Pet hybrids have emerged recently also from Joyce Stark ('Shortnin Bread', 'Fluffer Nutter' both P. forrestii x P. flaccida), Jeff Foerderer ('Milan', P begonifolia x P. nervosa) and Nagahide Nakayama ('Asa Blue' and 'Cv25', both re-makes of the 'Momo' cross by its originator). 'Cv 25' has lovely ruffled flowers that occasionally have extra petals.
I find that Pet symmetry and leaf forms really grow on you (no pun intended). Once, I thought they were a little ordinary. Now that I have acquired P. sericea, P. begonifolia, P. minor, (plantlets of 'Rosemary Platz' and P. rosettifolia from leaves and I am waiting for P. sp. 'Yumebutai' leaves) - I have really become a fan and I want more ('Cv 25' or 'Bantam' leaves anyone?)!
They take up little space and are unique additions to a plant collection. BTW, Tim also had some good cultural tips: Cooler temperatures are beneficial but not absolutely necessary... When wicking Pets need a very porous soil mix, they like it a little drier than AVs or rhizomatous gesneriads and Pets have very shallow roots. Tim thought bulb pans make good pots. Or recycled condiment containers if the plant is small. He said even an azalea pot can be too deep once the plant is ready for a 3" pot (pictured species from the show P. forrestii and P sericea).
[We were fortunate to have Tim as a speaker at our Chapter in March. He passed out a cultural sheet, which he has graciously allowed us to make available on the web. You can find it here - for permission to print etc., please contact Tim directly. --PT editor.]