I got 2 different varieties of butterfly bushes this summer and I don't know how to prune them. The guy at the nursery told me to be sure to cut them back to about 12-18 in. from the ground, but I keep reading that the bushes bloom on last years growth. Maybe I'm just not understanding. The blue one didn't grown alot, but had some nice flowers. The pink one really grew alot, but it didn't have hardly any flowers. Any help would be appreciated. If I prune, do I do it now or wait till March or does it matter? Thanks!
(sorry I'm new to all this, I think I posted in the wrong place