-
Flowers emerge before the leaves. Photo by the MDA. -
A group of flowers. Photo by the MDA. -
Flowers in a wooded understory. Photo by the MDA. -
A cluster of giant butterbur leaves. Photo by the MDA. -
Leaf is rounded and large. Photo by the MDA. -
A large leaf with a pencil for scale. Photo by the MDA.
Common Name: Giant butterbur, sweet coltsfoot, Japanese butterbur
Scientific Name: Petasites japonicus (Siebold & Zucc.) Maxim.
Related Species: Common butterbur
Legal Status
Three-year production phase-out period, after which sale of this species will be prohibited and the species will be designated as Restricted in 2029.
Background
Giant butterbur is a perennial forb native to Korea, China, and Japan. Leaf stalks are eaten as a vegetable in Japan, and it was introduced to North America for horticultural purposes.
Description
- Herbaceous perennial with huge leaves up to three feet tall and five feet wide.
- Large leaves are kidney-shaped and have dense hairs on the underside.
- Plants are dioecious (male or female). Although male and female flowers can be distinguished from each other, both grow on a terminal spike with yellowish-white clusters of daisy-like flowers that emerge before the foliage in the spring.
- Seeds are small with a tuft of white bristles on their ends.
- Reproduces by root fragmentation, creeping rhizomes (underground stem), and seed.
Habitat
Giant butterbur grows in shaded areas with moist soil, including riverbanks, shorelines, wetland edges, forested floodplains, and roadside ditches.
Means of spread and distribution
Giant butterbur plants are dioecious, meaning there are male and female plants. Viable seed has not been observed on the plants documented in Minnesota at this time. The plants have tuberous, fleshy, creeping roots and reproduce from fragments of these tubers, root pieces, and rhizomes.
Humans move root pieces through tillage, construction, and landscape plantings. In riparian areas where giant butterbur is growing, root pieces can move downstream during flooding. Seeds are wind dispersed due to feathery white bristles (pappi) attached to the seeds.
Impact
Giant butterbur has naturalized along riparian areas in Ramsey and St. Louis Counties in Minnesota, Washington state, and the provinces of British Columbia and Ontario. The plant grows aggressively and its large foliage shades out native plant species. Its large leaves shade out other plants, leaving the soil bare, which can contribute to erosion. Although populations recorded in Minnesota are small, it has the potential to change native ecosystems through aggressive growth and its ability to outcompete other plants.
Prevention and management
- Due to the plant’s spreading rhizomes, dig or hand-remove the entire root system and monitor for re-sprouting. The possibility of accidental spread is high because the plant can reproduce from root fragments.
- Herbicide applications may be effective. Foliar applications should be done during the active growing season. For herbicide recommendations, contact your local University of Minnesota Extension office.
Toxicity
N/A
