How to Grow and Care for a Butterfly Bush
Gardeners aren't the only ones who love gardens. Butterflies do too, especially when you grow fragrant, nectar-rich butterfly bushes. These woody shrubs, sometimes called summer lilacs, have arching stems and long flower panicles. They're available in colors like pale pink, raspberry, light lavender, deep purple, magenta, cherry red, sky blue, icy white, and ivory. Like the butterflies themselves, Butterfly bushes (Buddleia davidii, sometimes spelled Buddleja daviddi) can also be orange, yellow, and bicolored. Most are hardy in USDA Zones 5 to 9 or 10, where they mature at 5 to 8 or 12 feet tall and wide. Dwarf types that reach two to three feet tall are great for small spaces and containers.
There are a couple of things to know about butterfly bushes. While butterflies visit them to sip nectar, they're not a food source for caterpillars. Find out what kinds of butterflies are in your area, grow plants that their caterpillars will eat, and they're likely to hang around as they go through the different stages of their life cycles.
A butterfly weed (Asclepiadaceae, in the milkweed family) isn't the same as a butterfly bush, although butterflies are attracted to its bright orange flowers.
Also, butterfly bushes are considered invasive in some parts of the country. Check with your local extension service to be sure you can them in your area or look for non-invasive or seedless types.
When and Where to Plant a Butterfly Bush
Butterfly bushes do best when planted in early spring or fall, but you can add them to your garden in mid-summer, when the temperatures are hotter, if you keep them well-watered.
An island bed planted with a butterfly bush (or several) will help attract these lovely pollinators. Other places to use them include perennial beds and borders and cottage or wildlife gardens. Some have rangy, sprawling growth habits, so they don't make great specimen plants or focal points.
How to Care for a Butterfly Bush
Give your butterfly bushes eight hours of full sun. Six hours will suffice, although you may not get as many flowers. Full sun produces strong stems, so tall plants won't need staking.
Choose a planting site with well-drained, moist soil with average fertility. Since these plants take a pH of 5.5 to 8.5, and most garden soils range from 6.0 to 7.0, native soils are usually fine. If needed, mix some good organic compost into clay soil to improve its drainage, or add topsoil, peat moss, or compost to keep very sandy soil from draining too fast. Otherwise, amendments aren't usually necessary.
Dig a hole two or three times the diameter of the plant's root ball and place it in the hole no deeper than it was in its original pot. Backfill the hole and gently firm down the soil to remove any air pockets. Water thoroughly.
To discourage weeds and hold in some moisture, mulch with a couple of inches of pine straw or shredded bark. Don't let the mulch touch the stems, which can cause rotting.
Butterfly bushes can tolerate some drought once they're established but need consistently moist soil. When you water, water deeply, but avoid overwatering.
These plants seldom need fertilizing if they're growing in soil mixed with organic compost. If they're not, give them a balanced granular fertilizer in the spring, following the label directions for how much to apply, and water thoroughly.
Butterfly Bushes in Containers
Like butterfly bushes in the ground, container-grown Buddleia need moist, well-drained soil. Use a good quality potting mix and a container with drainage holes. Choose a container 8 to 10 inches wider than the plant's root ball so it can grow for a couple of years before it needs repotting.
How to Prune Butterfly Bushes
Prune in spring after new growth appears or anytime your plants get too tall or wide. Deadhead faded flowers as needed. Gardeners in northern climates sometimes cut their bushes to the ground in winter, although this can leave them susceptible to damage from the cold.
Common Problems with Butterfly Bushes
These tough plants are seldom bothered by pests or diseases but be ready to act if you spot a problem.
Rhizoctonia and phytophthora are fungal diseases that make leaves turn yellow and drop and lead to rotting stems and roots. To prevent them, don't overwater and or let the soil stay waterlogged. There are fungicides labeled to control these fungi, but even treated plants can still die.