7 Tips for Pruning a Butterfly Bush to Boost Flowering
One of the fastest-growing flowering shrubs, a butterfly bush can easily put on 5 feet or more of new growth in a single season. Learning how and when to prune a butterfly bush can help you keep all that vigorous growth in check. Regular pruning is essential not only for size management, but also is important if you’re growing an older cultivar that can reseed wildly and escape into native ecosystems. These butterfly bush pruning tips will help guide your cuts.
Because it reseeds prolifically, butterfly bush is considered an invasive plant in many areas of the U.S. Check with your local extension office before planting it. If it is invasive in your area, opt for one of the newer varieties that are virtually seedless or plant a native alternative.
When to Prune Butterfly Bush
The best time to prune a butterfly bush is in late spring, right after the buds swell and the leaves begin to emerge. Winter dieback is common on these shrubs in areas with very cold winters. By waiting until the leaves appear, you’ll know which parts of the plant survived the winter and can prune accordingly.
Tips for Pruning Butterfly Bush
When you’re ready to prune your butterfly bush, here’s how to make the best cuts to keep your shrub healthy and thriving.
1. If Invasive, Consider Removing
Butterfly bush (Buddleia davidii) is an introduced species from China that has escaped gardens and spread aggressively in natural areas across many parts of the country. So unless you’re growing a newer cultivar of butterfly bush bred to have near-sterile seeds, consider removing the plant altogether to prevent further harm to native habitats. Otherwise, be prepared to stay on top of removing faded flowers before they set seeds.
If you love the attributes of butterfly bush but want to grow an environmentally friendly variety, look for plants in the ‘Lo & Behold’ series and the ‘Miss’ series. These cultivars have sterile seeds so won’t spread aggressively.
2. Be Patient
Butterfly bush is one of the last plants to leaf out in spring. In colder regions, it might not show signs of life until as late as the third week in June. Give your plant time. As temperatures moderate and heat sets in, it will grow quickly. If there is no sign of life after the third week of June passes and the stems feel dry and brittle, your plant is likely dead.
3. Reduce the Size
The warmer your growing region, the more important it is for your butterfly bushes to be pruned back in spring. When it is not cut back, this vigorous shrub can easily grow to 20 feet tall with flowers only on the top of the canopy.
Begin pruning by removing about one-third of the shrub’s branches to ground level. When selecting branches to cut back, choose the oldest stems. Next, cut back all remaining branches to 3 feet tall or less. This pruning might feel extreme, but it’s essential to bring the flowers to eye level and give the plant good form all season long.
4. Remove Spent Flowers
Curb rampant reseeding by regularly pruning spent blooms. This practice is called deadheading. Cut the fading flower stalk back to the first set of leaves. New flower shoots will form below the cut. Deadheading also can encourage your butterfly bush to continue blooming into fall.
5. Don’t Hesitate to Prune Significantly
Butterfly bush tolerates extreme pruning with ease. Cutting an overgrown plant back to just a few inches tall in early spring is a great way to rejuvenate it. In colder Hardiness Zones, butterfly bushes often naturally die back to the ground in winter, and have no trouble regrowing from the roots.
Expect the shrub to regrow quickly once the weather warms up. It’s not unusual for a butterfly bush that is cut back to ground level in spring to stand 5 to 8 feet tall at the end of the growing season. Flowering won’t be compromised because this tough shrub blooms on “new wood,” which means stems produced during the current growing season.
6. Prune Smaller Cultivars Lightly
Many new, near-sterile butterfly bush cultivars mature at just 2 to 3 feet tall and wide. They don’t require significant annual pruning. Keep these small shrubs neat by pruning them lightly in spring to achieve a pleasing shape. Remove wayward stems and reduce the size as needed so the plant will complement the available growing space.
7. Make Time to Prune
Don’t be tempted to skip pruning your butterfly bush, especially large cultivars of this fast-growing plant. It takes less than 20 minutes to prune a single large butterfly bush. The relatively soft wood and easy-to-access branch structure make for quick work. Investing a little time pruning in spring will lead to a compact shrub with more flowers at eye level where they can be enjoyed from summer into fall.
