Arctium is a genus of biennial plants commonly known as burdock, family Asteraceae. Native to Europe and Asia, several species have been widely introduced worldwide. Burdock's clinging properties, in addition to providing an excellent mechanism for seed dispersal, led to the invention of the hook and loop fastener.
Plants of the genus Arctium have dark green leaves that can grow up to long. They are generally large, coarse, and ovate, with the lower ones being heart-shaped. They are woolly underneath. The leafstalks are generally hollow. Arctium species generally flower from July through October. Burdock flowers provide essential pollen and nectar for honeybees around August, when clover is on the wane and before the goldenrod starts to bloom.
Burdock's clinging properties make it an excellent mechanism for seed dispersal.
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 Arctium and Cousinia are hard to define; there is an exact relation between their molecular phylogeny. The burdocks are sometimes confused with the cockleburs (genus Xanthium) and rhubarb (genus Rheum).
The following species are accepted:
Arctium abolinii
Arctium alberti
Arctium × ambiguum
Arctium amplissimum
Arctium anomalum
Arctium arctiodes
Arctium atlanticum – Algeria, Morocco
Arctium aureum
Arctium chloranthum
Arctium dolichophyllum
Arctium × dualis
Arctium echinopifolium
Arctium egregium
Arctium elatum
Arctium evidens
Arctium fedtschenkoanum
Arctium grandifolium
Arctium haesitabundum
Arctium horrescens
Arctium karatavicum
Arctium korolkowii
Arctium korshinskyi
Arctium lappa – greater burdock – much of Eurasia; naturalized in North America, Australia and New Zealand
Arctium lappaceum
Arctium × leiobardanum – Siberia
Arctium leiospermum
Arctium × maassii
Arctium macilentum
Arctium medians
Arctium minus – lesser burdock – Europe and southwestern Asia; naturalized in North and South America, Australia and New Zealand
Arctium × mixtum
Arctium nemorosum
Arctium nidulans
Arctium × nothum – central and eastern Europe
Arctium palladinii – Turkey, Iran, Caucasus
Arctium pallidivirens
Arctium pentacanthoides
Arctium pentacanthum
Arctium pseudarctium – Afghanistan, Tajikistan
Arctium pterolepidum
Arctium radula
Arctium refractum
Arctium sardaimionense – Tajikistan
Arctium schmalhausenii
Arctium × semiconstrictum
Arctium tomentellum
Arctium tomentosum – woolly burdock – northern and eastern Europe, Turkey, Iran, Caucasus, Siberia, Xinjiang; naturalized in North America
Arctium triflorum
Arctium ugamense
Arctium umbrosum
Arctium vavilovii
Arctium × zalewskii
Circa 16th century, from bur + dock, the latter meaning sorrel of the genus Rumex.