Bad for butterflies, no. Bad for the local ecosystem, maybe. But there are steps you can take to offset potential problems.© Zen Rial/Getty Images
The fact is, butterflies love butterfly bush (Buddleja davidii), which reliably produces nectar-rich flowers for a long period of time. Gardeners love it, too, because it’s tough, undemanding and offers plenty of those aforementioned flowers.
The Problem With Butterfly Bush
Problem is, those flowers eventually turn to seed. And before you know it, butterfly bush is on the march. Sometimes it’s moving just across your yard, sometimes it’s launching seedlings all over the place — including wild areas, where it crowds out native plants. Because of this, butterfly bush is considered an invasive pest in some parts of the country, particularly in the Northeast and Northwest.
How to Avoid an Invasion of Butterfly Bush
There are solutions, but they come with their own set of caveats. First, be vigilant about deadheading flowers. Clip them as soon as they fade so they don’t produce seed. Be sure to collect and dispose of spent flowers. The same goes with trimmings because cut stems can take root. With that in mind, it’s a good idea to mulch bare soil to discourage accidental rooting.
To cut down on self-seeding, plant a variety with fewer viable seeds. For example, ‘Summer Rose’ and ‘Orchid Beauty’ produce 20 times less viable seed than ‘Potter’s Purple’ and ‘Border Beauty,’ according to Oregon State University. Hybrids such as ‘Lilac Chip’, ‘Miss Molly,’ ‘Miss Ruby’ and ‘Miss Violet’ generally have low fertility as well. (Note: They are sometimes marketed under the name “summer lilac” rather than “butterfly bush” to differentiate from invasive varieties.)
Another solution is to grow a sterile cultivar such as Lo and Behold ‘Blue Chip’ or ‘Purple Haze’. Here is a list of approved sterile butterfly bushes from the Oregon Department of Agriculture.
This Can Alleviate the Need for Butterfly Bush
If you’re intent on attracting butterflies to your garden, you should think about succession planting — that is, make sure to have something blooming at all times. One of the reasons butterfly bush is so popular with gardeners is because its long season of bloom takes some of the guesswork out of succession planting. Remember, though, that butterflies need more than nectar to complete their lifecycle. Butterfly caterpillars need plants to feed on including dill, milkweed and parsley.
As for growing butterfly bushes, give them full sun and well-drained soil, as they are prone to root rot in heavy, poorly draining clay soils. Hardy in USDA Hardiness Zones 5 through 9, butterfly bush is a woody plant in the South but behaves more like a perennial where winters are cold. That means the tops of plants die back, but new shoots arise in the spring and still flower that year.