Question
how do i prune my butterfly bush?

Answer
Butterfly Bushes MUST be pruned hard every year.  Skip pruning and these shrubs will become wild, surly purple monsters with lots of branches and fewer blooms.  A good chop to 2-3 feet will keep it civilized and booming with blooms.

But like most shrubs, you can mess this up just by pruning the wrong time of the year.

Pruning now is risky business.

That's because Butterfly Bushes bloom on current growth.  This is a task that should be performed in EARLY spring.  About a month ago.

Severe pruning now may interfere with at least some of performance.  A dose of spring fertilizer will help generate more new wood for more flower power.  If you have a Buddleia that has gone several years without a visit from the pruning shears, make sure you are a little kinder than usual -- chop off a maximum 1/3rd of the lengths of the canes.  More would be too much.  In 2 years, repeat.  Remember, this is a task that should be done every other year for best results.

Don't delay.  The sooner, the better.  If you have to stand in the rain to do it tomorrow, so be it.  Every day you wait will be flowers lost.

Thanks for writing.  Any questions, I'm here.