Arctium tomentosum
Arctium minus
bardane tomenteuse, cotton burdock, woolly burdock, woolly burrdock
bourrier, burweed, button-bur, chou bourache, cibourroche, common burdock, cuckoo-button, lesser burdock, lesser burrdock, louse-bur, petite bardane, wild rhubarb
petioles hollow or solid, 10–15 cm, glandular-hairy;
blades 30–40 × 16–28 cm, coarsely dentate to subentire, abaxially white-tomentose, adaxially green, sparsely short-hairy.
petioles hollow (sometimes only at base), 15–50 cm, thinly to densely cobwebby;
blades 30–60 × 15–35 cm, coarsely dentate to subentire (rarely deeply dissected), abaxially ± thinly gray-tomentose, adaxially green, sparsely short-hairy.
1.5–12 cm.
0–9.5 cm.
15–25 mm diam., densely cobwebby (rarely glabrate).
15–40 mm diam.
30+;
corollas rose-purple, (occasionally white), 9–13 mm, limb minutely glandular.
30+;
corollas purple, pink, or white, 7.5–12 mm, glabrous or limb glandular-puberulent.
linear to linear-lanceolate, inner usually purplish, margins with minute spreading or reflexed glandular hairs.
linear to linear-lanceolate, glabrous to densely cobwebby, inner often purplish tinged, margins often minutely serrate with fine teeth, puberulent with glandular and or eglandular hairs.
usually in corymbiform clusters, long-pedunculate.
in racemiform or paniculiform clusters, sessile to pedunculate.
light brown, 5–8 mm;
pappus bristles 1–3 mm.
dark brown or with darker spots, 5–8 mm;
pappus bristles 1–3.5 mm.
= 36.
= 32 (Germany), 36 (as A. nemorosum).
Arctium tomentosum
Arctium minus
Arctium tomentosum has been reported from Illinois, Iowa, Maryland, New Jersey, Oregon, Pennsylvania, South Carolina, and Wisconsin; I have not seen specimens.The involucres of Arctium tomentosum are usually very densely cobwebby.
Exceptional forms of A. tomentosum have nearly glabrous involucres. Forms of A. minus with especially cobwebby involucres have been misidentified as A. tomentosum; they lack the corymbiform capitulescence and glandular corollas of the latter.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Arctium minus has been reported from Delaware and Texas; I have not seen specimens.
Arctium minus is a complex species with many variants that have been recognized at ranks ranging from forma to species (J. Arènes 1950). Some North American workers (e.g., R. J. Moore and C. Frankton 1974) have often distinguished plants with involucres more than 3 cm diameter that equal or overtop the corollas as A. nemorosum. Arènes treated those plants as a subspecies of A. minus. Arctium nemorosum was recognized as a species distinct from A. minus (H. Duistermaat 1996), with a different and more restricted circumscription than that used by North American workers. Although most of the characters that Duistermaat used to separate those A. nemorosum from A. minus overlap extensively, the consistently wider mid phyllaries of A. nemorosum (1.7–2.5 mm wide versus 0.6–1.6 mm in A. minus) supposedly distinguish the species. None of the North American specimens examined in preparation of this treatment had the wide phyllaries of A. nemorosum in the sense of Duistermaat, who stated that she had seen no material of this taxon from the American continent. Some American authors have taken up the name Arctium vulgare in place of A. nemorosum and applied A. vulgare (dubbed woodland burdock) to the larger-headed North American plants. Duistermaat considers A. vulgare to be a synonym of A. lappa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
