Pruning a butterfly bush

In spring, you will see lots of new shots emerging - prune to leave just two on each stem (one to grow and one as insurance against a late frost)

Last year, I pruned mine down to about 12" from the ground and was scared I'd pruned it too hard - but no, it sprouted out and had flowers just a bit later than normal. This year I wasn't quite so ruthless and it's doing just fine. So - it'll be OK! Just don't chop it right off and leave an ugly stump. LOL ....Follow what Andrew said.

I think you can cut down to a single stump and it will soon shoot out again. They do so much better if kept well pruned.

I prune mine to about 12"-18" in Spring, as long as you see the new shoots coming you wont have a problem. If you dont cut back each years growth you will have an out of control very large bush.

I often see those around, don't you, Poppy? I always feel like knocking on the door and offering to prune it for them!!!! LOL.

I prune mine down gradually as the flowers go over and then, at the end of October, prune it down to 2 or 3 main shoots about 2 ft. from the ground. If you don't prune it enough you won't get those lovely big sprays of flowers in the summer and, as said previously, you will soon have a seriously big tree that is out of hand.