Q: When and how do I trim a butterfly bush so it will bloom again? --John Johnson, Lincolnshire A: Prune all the above-ground stems and branches to the ground before plants resume growing. In the Chicago area, butterfly bush (Buddleja davidii) is a die-back shrub. Plants growing in well-drained soil are hardy in Zone 5, but only the roots and crown survive winter. Butterfly bush will begin flowering on new shoots in midsummer. Snipping spent blossoms will encourage plants to flower and attract butterflies until the first hard frost.
Robin Carlson, Chicago Botanic Garden
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