We prune ours severely down to about 2 feet from the ground , I believe in february, when spring arrives it sprouts new growth up so fast !! We could almost see it grow inches every day it seemed to... about 12 feet in height ! It was beautiful , the bees and butterflies love it ... I can't wait till spring !

Jan/Feb. Down to 2 feet or even less. Or maybe try three feet.

The key is that it needs to be dormant. I do mine some time around Feb or March. Same time I do the Crape Myrtle and Pee Gee Hydrangea.

I prune mine late fall-it's not quite dormant but the flowers are all dead. Mine is near a fishpond-I don't want the dead leaves to blow into the pond during winter.

My deer decided the best time was last late last fall after other foliage had died off. Right now (1 March) they are getting around to pruning the spruces.

DO IT NOW! Don't delay like I did last year - I have two 10-ft tall butterfly bushes now. They're waaaay out of control. I'm waiting for a "good" day (I'm undergoing chemo right now so I tire out early - see MAGTAG 2009 post) to tackle this.

Actually, you might want to wait until this predicted sleet storm is over with, come to think of it.

I hope you got your butterfly bush pruned. There is one in my neighborhood I admired last year that was the size of a small tree. The weight of the snow on the branches last week cracked half of it right off!