Will they grow here or is it too hot?
Rex Begonias in the TX
If you keep a very close eye with the watering and they are potted inground or in pots in full shade they will do well. However, IME, they still get ratty-looking in the hottest part of year. I think they might be easier to grow as houseplants.
Hey Vossner! We're making the same rounds!! ;-D
I have rex begonias in pots, protected under my port-a-cachere. Last year I had a lot of problems with them - they got a bacterial blight and the leaves would get all nasty blotchy. I had to take most of them off. The trick (I think) is to not let any water get on the leaves. Water carefully - not overhead. So that eliminates putting them out where they can get rain on them. They also need good air circulation. I cut them back and took them into my basement over winter, and the leaves grew back and they are back outside, protected. So far, so good. I haven't used the copper fungicide (Kocide) that is recommended for bacterial leaf spot - trying to manage it culturally, which I think is better, if it can be done. Don't let them get leggy; pinch them back to keep them full. If you don't, they WILL look ratty by July.
I agree, I had some in pots on the patio and as soon as they looked good the leaves would get attacted by something and I would have to cut them back again. Finally I left all three out on the porch last year and they froze solid. I have given up on them as an outdoor plant.
Keep the Rex Begonias in containers and be sure that the containers have lots of drain holes. I drill more drain holes in containers that do not have a lot. If the containers have their own drip saucers attached to them at the bottom, remove them. I have found it is best to not top water Rex Begonia at all. Place the container in which they are growing in a water filled larger pan or pot (that holds about 2 or 3 inches of water) and let the water soak up from the bottom for several hours. Do not pl;ace a saucer under them or drain any water from it. Now while it is still cool, they will be fine. When the weather gets really hot, I move them inside where they receive a lot bright light, but no sunlight. Also, I remove lower leaves that start completely touching the soil. Cut off immediayely any leaves that start to look wilted and any dead leaves. I have killed a lot of expensive Rex Begonia before following the steps above. :o)