Answer: Butterfly Bush, also known as Buddleia davidii, blooms on new growth. Therefore, stems should be pruned back in early spring to encourage large, lush flower spikes. You can let it grow into a shrub form, (which could eventually be about 12'x15') but your flower "show" won't be as spectacular. FYI, I always prune back my Butterfly Bush on St. Patrick's Day to about 6-10" .
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