Did you know that there are 3 invasive plants on Kauai that are all called “butterfly bush”?
The Buddlejas, or plants in genus Buddleja (pronounced bud-lay-a), are medium-tall shrubs with colorful inflorescence (flowering structures). The flower structure is comprised of large numbers of tiny tubular flowers packed into dense clusters or pannicles.
The flower color varies by species, but are all typically rich in nectar and often have a sweet or honey-like fragrance. These plants are strong attractors to butterflies, hence the common name “butterfly bush.” However, despite providing rich nectar, they are not good habitat for butterflies since butterfly larvae do not survive on them. The plants do not provide food for the larvae and may out-compete other plants that the caterpillars depend on.
Buddlejas are often grown as garden ornamentals; however, many species are known for their invasiveness. In particular the three we have on Kauai have become problematic.
Buddleja madagascariensis, butterfly bush, is sometimes also called smoke bush. Native to Madagascar, it is an aggressive sprawling shrub which has naturalized in a wide range of climate zones and is invasive in Hawaii, forming impenetrable thickets that crowd out other vegetation. Dried portions of the plant can cause throat allergies, coughing, and eyelid blisters in susceptible people. A large invasive population is found in Kokee forest and it is also still occasionally cultivated in Kauai yards.
Buddleja davidii or orange-eye butterfly bush, is native to China and Japan. It forms dense thickets on disturbed or compacted soil and produces numerous wind-dispersed seeds that can travel long distances. It is naturalizing at higher elevations on Kauai including Kokee State Park.
Buddleja asiatica or Asiatic butterfly bush, is also called dog tail. This plant colonizes disturbed areas, stream areas, or open woodlands, and has proven to be one of the worst weeds for forestry managers in New Zealand. In Hawaii, it is highly invasive and has naturalized in mesic to wet forest from 300 to 4000 feed. It is found in central and northwest areas of Kauai.
All three of these plants are on Kauai’s Pono Program Blacklist. They are being controlled in Kokee by the Kokee Conservation Resource Program. Please do not plant them! Any of our island’s Pono-endorsed nurseries or landscaping professionals can give advice on good alternatives to use for garden plantings. Mahalo!