The genus Arctium has discoid flower heads, and globular involucres. The flowers, usually purple, are followed by roundish many-seeded burs. The involucral bracts. (phyllaries) are attenuate to long, stiff, with hooked tips. The seeds have a pappus. The leaves are large and coarse. The Arctium species flower from July through October. The genus belongs to the Asteraceae family.
Arctium is a biennial native in temperate Europe and Asia and is an introduced and mostly weedy plant in North America. Its taxonomy is still evolving. A large number of species have been placed in genus Arctium at one time or another, but most of them are now classified in the related genus Cousinia. The precise limits between the two genera are hard to define. Up to four species and two hybrids are usually recognized in Québec:
The two species, simple enough to recognize and agreed upon by most taxonomists are Arctium lappa and Arctium minus, the only two that will be dealt with in theses pages. Both species are similar in appearance and were introduced from Eurasia. It is a biennial weed that can grow up to 2 meters tall. The roots of Arctium lappa are widely used for herbal medicinal purposes such as blood cleansing, urinary tract infections, skin ulcers and arthritic conditions and first year roots known as Gobo are eaten as a vegetable in Japan. This invasive species can also taint milk if animals have grazed large quantities. Arctium seeds have also been problematic for livestock because of the hooked seeds. They become entangled in animal hair for several weeks before drying out and falling off. The hooked seeds are able to disperse quite readily. It is largely found in disturbed soils along roadsides, streambanks, creeks, farms and grassland areas.