Can you tell us what it is you want to prune?

Yes you can cut your Buddleia back by a third now and cut back even more next spring.

Sorry, didn't notice the link!

I'd like to know where that poor spelling is on our site and correct it!

If its Buddleia davidii, reduce the top a bit now if you're worried about windrock over the winter, but otherwise, prune back to within 2 inches of this year's growth last week of March - every year.

If it is B. alternifolia or B globosa, I would prune it back lightly (less than 1/5) now, to reduce wind rock, and do the heavy pruning right after it flowers, to allow plenty of time for new stems and flower buds to develop before fall. Heavy pruning in March on these species can prevent blooming.