Astilbe
by Dorothy
(Alberta Canada)
Doug says to pot it up. Keep it as cool and bright as you can afterwards. And I hope you got a really good price on it because otherwise you're about to set it back quite a bit. In the spring when you do put it into the ground (after all danger of frost) plant.
At this point you can either leave it grow tall and ugly, stretched out etc for the season and the following year (2011) it will be fine.
Or, cut it back to the ground and get it regrowing this year - if the root is strong enough, it will produce a flower. If the root is not strong enough - and those packaged roots seldom are - you'll cut off any attempt at flowering and let the plant develop great root strength.
Me? I'd cut it back and not let it go to flower and then go for flowering the next year.
So while the plant may have been a bargain in price, it's not in performance.
Good luck with it