I've finally gotten just a few seeds of B. alchemilloides to germinate, so hopes are renewed for little miniature tuberous begonias I want to create from it. Once it got past the second true leaf it started growing well. From the picture, if I were naming it, I might have picked "saxifragoides" instead:

http://www.brazilplants.com/begoniaceae/begonia-alchemilloides.html

B. sp 'Caparaó' is another smallish one. It has fun peltate leaves, which I would like in miniature begonias too. It looks like it may be rhizomatous from this picture:

http://www.brazilplants.com/begoniaceae/begonia-caparao.html

It was my third and last sowing, the last seeds in the packet of 'Caparaó'. One lonely seed germinated, and it's now working on its third leaf

I'm sure there are more small Begonia species out there too, I'll be looking and listening for species that are in the size range of miniatures especially!

Vincent

Here are some small species that you might consider:

prismatocarpa - very tiny leaves
U502 - seems a bit slow growing but leaves are no bigger than an inch or less
U514 - small rounded maroon leaves, very floriferous
U074 - vining habit, a bit mildew sensitive but still have hopes for it, flowers easily
turrialbae - wasn't impressed early on but now under cover it is growing into a nice jewel but the leaves have doubled in size since I have it under cover (1 to 1.5 inches)

I do like prismatocarpa.. I accidentally let it get smothered out, in the Bertolonia projects, I think. 'Buttercup' is still going, but it's larger. The others you list are all unfamiliar, and sound like the small-terrarium size I would look for. I'll definitely be looking them up!

The B. alchemilloides is growing very well for me. Coin sized leaves, and the first little flower bud is 2-3 mm across. The brown edges were the instantaneous result of fertilizing the night before a heat wave baked the room. Oops. I'll be trying leaf cuttings of it soon to see when and how tubers develop. (Sneaking into the picture are Bertolonia marmorata 'Sanderiana' to the Left, and Phinaea ecuadorana to the right.)

B sp. 'Caparaó' is cute, but barely growing. I risked a little bit of dyna-grow on it when I fed the other things in the terrarium, to see if it would pick up the pace a bit. Maybe it needs limestone or something. I'm afraid to mess with chemistry when I only have one, very tiny, plant.

Vincent

Your B sp. 'Caparaó' looks a tad wet in that picture. Hopefully it will start growing. How many seeds of that variety did you plant?

The Begonia are actually all in pots, so I can move them around- as are most of the other plants. This whole (55g) terrarium is basically a seedling and cutting nursery. I need to pull out a bunch of weeds, which I now think may be a Peperomia- and yes, also hack back some Episcia.

Yes, the Caparaó plant was wet at the time of the picture, I had just watered it- and saw in the picture that the water splashed soil over the crown, so I squirted that off too. I don't keep it that wet. The soil mix is much lighter than it looks in the picture, too. I might try pricking it out into a blend with chopped sphagnum, though. Or it might just be the Begonia seedlings' way of sitting and doing very little for a long time, then they get to some kind of critical mass and suddenly start growing more quickly.

I planted a few sowings of the Caparaó collection over a couple years, probably a couple dozen seeds, but only got this one to germinate. It was the last of the seeds, and had been in a refrigerator for that whole time. I've left the seedling tray alone just in case, but I don't expect any more to germinate. Begonia seed is usually easy, I figured this batch might just be old. I was surprised to get the several alchemilloides from this sowing.

These came from Mauro also. I have great luck with his seeds in general.

Vincent

These are looking good. I'm interested in hearing about your breeding plans with alchemilloides.