Answer: I don't think you'll be successful in training butterfly bushes into tree forms. The roots tend to clump and enlarge as the plants mature, sending new stems up from the root system to help renew the plant. If you tried to train the plant into a single trunklike stem, you'd be forever battling sucker type growth at the base. Butterfly bushes are typically cut down to soil level every few years to remove the oldest, non-productive stems and to encourage healthy new growth. Wish I could be more encouraging about your idea!
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