E-Flora BC: Electronic Atlas of the Flora of British Columbia

Petasites japonicus (Siebold & Zucc.) Maxim.
Japanese butterbur (Japanese sweet coltsfoot)
Asteraceae (Aster family)

Introduction to Vascular Plants

© Adolf Ceska  Email the photographer   (Photo ID #13608)

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Distribution of Petasites japonicus
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Species Information

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Perennial herb from a creeping rhizome; stems erect, branched above, numerous, sparsely long-hairy to thinly woolly-hairy, 0.2-1.0 m tall; flowering stems appear before the leaves.
Basal leaves arising directly from the rhizome, thick, round to heart-shaped on long stalks, shallowly to conspicuously toothed, usually with 20 or more teeth per side, white-woolly to nearly glabrous beneath, green and somewhat hairy above, the blades 20-40 cm long, 10-60 cm wide; stem leaves reduced to parallel-veined bracts, 1-8 cm long, reduced upwards, sparsely long-hairy.
Heads disciform in elongate to flat-topped clusters, stalks moderately to densely white-woolly; involucres 6-12 mm tall; involucral bracts lance-shaped with hairs at the base, green, sometimes with translucent margins; disk flowers whitish.
Achenes 5- to 10-ribbed, glabrous; pappus of white, hairlike bristles.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist ditches and fields in the lowland zone; infrequent in SW and SC BC; introduced from Japan.

Source: The Illustrated Flora of British Columbia


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Nardosmia japonica Siebold & Zucc.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References