I have mine in part shade. I think too much sun will burn it , but too little and it will not bloom well. It is not a hugely xeric plant. somewhat xeric . Mine gets mid day sun.

I planted two that I got as small plants at the LBJ plant sale last fall. They have both grown very well and get plenty of sun. I do think they need some water though in the hot weather. They were only 4 inch pots and are now in the 3 foot range and seem to like our sandy soil in Freestone County. I did put some crushed oyster shell as a top dressing to mimic it`s native habitat. It is a facinating plant to me due to the fact that it was thought extinct until `86 or so when it was rediscovered. Good luck with yours. I`m curious to see if mine will reseed.

Here is a link that might be useful: Randy Hyden`s Life Blog on the Post Oak Savannah

I have heard that it was originally found on a stream bank in the Hill country. The LBJ wildflower center has it listed as liking Sun to partshade and moist soil. It is pretty dry ay my place and it gets very little water, so it is not huge and fasy growing. I think it is semi xeric and it will survive periods of dry but is much happier with regular water.