The butterfly bush weed (Buddleia davidii) attains a height of 15 feet. It forms long, arching branches with showy flower spikes that measure up to 10 inches in length. Blossoms appear in colors of red, orange, purple, lavender, yellow and white. Flowering begins mid-summer and runs until the first hard frost of fall. The bush easily colonizes and invades with aggressive tendencies when it escapes cultivation. It becomes a dangerous noxious weed when pitted against native plants.
Impact on Butterflies
Imported from its native China, the butterfly bush became a popular ornamental garden plant. The bush attracts numerous species of butterflies with its abundant flower clusters and fills the garden with sweet fragrance. It attracts numerous butterflies but also poses a threat to their survival. The butterfly caterpillars do not feed on the bush. The caterpillars feed predominately on the native plants that the butterfly bush quickly chokes out and kills with its aggressive growth. This means that the life cycle of the butterfly is disrupted and might cause the loss of many caterpillars.
The butterfly bush arrived in Britain in the 1890s and became a favorite garden shrub. The shrub escaped cultivation and become a serious noxious weed. The bush is also invasive in New Zealand. The state of Oregon has officially declared the butterfly bush to be a noxious weed, according to the Oregon Department of Agriculture.
The butterfly bush produces large amounts of small, winged, lightweight seeds. Seed production begins early for the shrub and often occurs during its first year of life. Dispersal occurs by the wind, wildlife and water. The seeds remain viable for three to five years, according to Washington State University. The bush also reproduces vegetatively. The cut stems of the butterfly shrub take root when they come into contact with soil.
The seeds germinate in dry locations. They grow along roadsides, riverbanks and within cleared forest. The shrub poses a serious threat to riparian (along waterways) areas and threatens areas undergoing forest regeneration because it chokes out newly planted tree seedlings.
People can help control the spread of the butterfly bush weed by removing all flower heads before they have a chance to go to seed. Using herbicides such as glyphosate works moderately well. The shrub should be cut to the ground before applying herbicide for the most effective control. When cutting back the butterfly bush weed never leave the branches on the ground or they will quickly sprout and produce new shrubs.