Astilbe did not like our hot conditons too, so in my area, it is just good for late winter to early spring. I have it before in containers, thinking I can reposition it to help get more shade. After it really goes brown and ratty, I just let it dry off and cut off. Eventually, I gave up on it. Too bad, nice looking plant when conditions are cool and part sunny.
So far in my very hot and part shade garden, Caladiums are doing very well, just got to water often.