As you're already discovering, these alpine genera are not well-suited to the heat and humidity of the south. They should be given excellent drainage and the coolest spot you can possibly provide, maybe in a north-facing rock garden.

If you want to grow hardy gesneriads, in zone 7b you should be experimenting with some of the more warm temperate/subtropical gesneriads, especially some of the new ones coming out of China. Among these are Corallodiscus, Tremacron, Raphiocarpus, Didissandra, Briggsia, and maybe even some Chirita species. Unfortunately most of these are not yet widely available and have not been well-tested for hardiness. From the New World, many Sinningia species and hybrids are proving to be hardy in zone 7b, and can take full sun and heat.

Thanks, John - sorry to be so late in acknowledging the response; I just stumbled upon it recently. I agree about the temperature issues re. the alpines; this summer I grew them indoors under lights in an air conditioned bedroom (with pots plunged in sand in an empty aquarium for humidity), and some have survived. Haberlea rhodopensis is the only definite casualty so far, so that's it for me there - I have a rule that once I've killed something 3 times, I give it up. The seedlings are holding their own, but not increasing much in size. I will put all of these in a cold frame for the winter, if cooler temps ever arrive.

I've been growing lots of the other things you mentioned outdoors - many Sinningias are indeed hardy here, and I've even successfully overwintered some of the miniatures (winter drainage seems to be key)along with certain Achimenes, Gloxinia nematanthoides, Titanotrichum, and Eucodonia. This winter I'm trying Seemania sylvatica, Tremacron, and Hemiboea subcapitata.

Any ideas on propagation of Tremacron? I have one plant which has done well so far, but I hate risking it without having replacements on hand. Have tried leaf cuttings with no success so far, and I'm watching a couple of seed pods now (missed the last batch- my jobs keep getting in the way of my gardening).

Thanks so much for your assistance!

I just found this website searching for how to propagate Hemiboea subcapitata. I received a cutting in the mail today and I'm not sure what to plant it in. Right now it's in some long sphagnum moss that I use for my orchids. I had to cut off two leaves so it would have nubs. Leaves are also in the moss. Any help would be appreciated.