They are great plants, beautiful in bloom if you can nurse them thru the flowering season. They want to bloom in May here just about the time it gets too hot for them. If you water them heavily they may bloom well. Otherwise the flowers will start out OK and then turn brown.
Since they are heavy feeders they need lots of humus in the soil when planted. I usually fertilize before they bloom and mulch them with composted horse manure (free) after they finish.

Thanks steveh, I'm hoping they wind up looking something like the picture on the package. It'll be a treat to have something more colorful in the shady areas.

Yeah...definitely stay generous with the organic matter. Mine are quite sensitive to the heat. Beware that the tree roots will compete with the plant for its water resources. Around here, unless you have a dense forest in your yard the environment under trees is usually a dry shade.

Good luck! They are beautiful and should get bigger and better each year.

I tried astilbe's in my shade yard under tall pines. Between the root competition and drought, they bloomed very poorly and died over the winter. They definitely like a lot of water, I've been told, and with the drought that we've been having, it's hard to give them enough that the trees don't suck up. Good luck. Hope you have been luck than I do. I heard Erica Glassener on Gardener's Diary, I think it is, say that Astilbe's don't like the hot south. I don't plan to try them again.

Hmm, I'm thinking that maybe the natural area under the trees might not be wet enough based on everyone's comments. I've got to start working on "Plan B" :-) Thanks for all the help. I'll see how it goes this year. It's worth giving it a try.

Mine have done better in a very humusy soil that holds water, gets morning sun but is still elevated for drainage. My experience is they like moisture but don't much care for waterlogged clay.