Q: I love my butterfly bushes, Buddleias, but they do grow very tall and tend to be spindly. How should I prune them, and will it hurt the blooms this summer?
A: Buddleias are one of the most floriferous of the summer-blooming shrubs. As you can tell by their common name, they attract butterflies by the dozens all season long.
Your Buddleias should just be coming out of their winter dormancy with new leaves. Flower buds should be forming soon, and they will undoubtedly bloom earlier this year due to the unseasonably warm weather. All of the older varieties of Buddleia davidii tend to grow tall and open with flowers at the tips of new growth, as you describe.
If you prune the old woody stems of your Buddleias down to 12 to 18 inches tall, they will produce more branches that are lower, and regular clipping will make them bushier. Keep clipping the flowering tips, and the blooms will continue as well.
You can feel free to prune your Buddleias every two or three weeks, and then give them a shot of flowering fertilizer (say 15-30-15). This will keep them full of flowers and bushy all summer long. Buddleias may not be as long-lived as some flowering plants, but they make up for it with consistent blooms all summer.
You might want to search your local nurseries for new ranges of Buddleias that are very dwarf. These new named varieties grow as short, many-branched, rounded shrubs. There are two named groups: the Flutterby series that stay as small as a bushy 3 to 4 feet. The other series, called Lo & Behold, stay short and full with silvery colored foliage and numerous small blooms.
Both have color ranges in white, pink and blue shades. These plants have been tested and found to be sterile, so they will not be spreading rampantly through your garden. Plant these very dwarf groups in front of your leggy Buddleias. They will conceal gangly stems with constant flowers.
Email Pat Lea at firstname.lastname@example.org.