Then I remove spent blooms all during the growing season, and our plants flower until frost. Summer blooms are fewer and smaller, but they are still there. Because the soil is rich in organic matter, there is little need to fertilize, but I occasionally apply fish emulsion to boost nutrients.
Butterfly bush likes partial sun, good drainage and room to grow.
Water during hot, dry spells, but don't overdo it. As you've likely found, a host of butterflies love this plant. I prune away frost-bitten stems before new growth begins. Should the plant survive the cold undamaged, I prune it back in spring to encourage fuller growth. It's said that removing spent flower heads helps promote more blooms, but I rarely even do this.