The butterfly bush, also known as buddleia, requires pruning in late winter or early spring, according to the Old Farmer’s Almanac. Some gardening experts recommend pruning the plant all the way to the ground, while others avoid cutting into old wood. If pruning hard in the spring, remember that buddleia remains dormant late.
Buddleia is easy to care for, especially when it comes to heavier pruning. It’s very hardy, so rather than stunting it, hard pruning encourages lush new growth. Since buddleia’s stems are hollow, put off pruning until after the last frost to keep ice from forming close the bush’s core. Watch the bush carefully after a hard spring pruning because new growth doesn’t bud until much later than other plants. A second light pruning during the summer encourages more flower spikes.
Unless the buddleia outgrows its space in the garden, pruning may not be necessary at all. When left to grow, buddleia becomes a tree with a rugged, peeling trunk. While the buddleia is in bloom, to attract more butterflies and bees, encourage new blooms by dead-heading and removing dead flower spikes. Late in the fall, let the last flowers go to seed to provide winter forage for birds and other animals.