I am not sure my shade-cloth would stand up to grapefruit hail, Cameron. I have lived in the Deep South my entire 75 years and have never seen hail like that. I can sure see your hesitation when it comes to building shade structures. A nice shadehouse can be built fairly inexpensively though. The temperatures that you quote are not even problematical when growing the vast majority of orchids. My orchids have been subjected to the upper 30's this year and they haven't really missed a beat. They are all under trees, under screening (lanai) or under shade-cloth though, so there's little danger of frost.
