hi nancy.

what is the height range of begonias you want to use?

w/o knowing that...

'Plum Gorgeous,' 'Caribbean Corsair,' 'Boomer,' might be good ones. various canes can offer a lot of burgundy/silver, too. i don't know if it'll like the heat and humidity, but 'Benitochiba' is excellent for those colors.

i'm not familiar with growing begonias in the ground in the south, but i imagine others on here would have a better idea. try looking through the link at bottom. they're in miami and have a nice selection.

-ming

Here is a link that might be useful: begonias

They would have to be fairly small. It is between two fairly small trees. My canes are 7-8' tall. Unless there is a way to trim them and still have blossoms.
Thanks,
Nancy