The Thistle Group
Asteraceae
Contents English Names Index
 
Thistles have spines on stalks and leaves
Burdocks have spiny hooks on the bracts
Flowerheads have disc florets only, usually purple in color
Thistle leaves are alternate, finely divided
Burdock leaves are alternate and heart-shaped
 
Guide to Identify Presented Species of the Thistle group
FLOWERS PURPLE
Arctium minus - Common Burdock
Stout, coarse, branching biennial, up to 150 cm tall. Disturbed areas.
Flowerheads purple, round, bur-like, with hooks, 15-25 mm wide, clustered.
Leaves large, ovate to heart-shaped with thin, woolly hairs underneath.
Carduus nutans - Nodding Thistle
Robust biennial, 30-250 cm tall. Stems leafy and winged, spiny. Disturbed areas.
Flowerheads solitary, nodding, purple, 2-5 cm wide. Bracts long, spine-pointed.
Leaves alternate, lance-shaped, deeply pinnately lobed, with spines.
Cirsium arvense - Canada Thistle or Creeping Thistle
Perennial, 30-150 cm tall. Stems leafy, branched, not winged. Disturbed areas.
Flowerheads pink to purple, 12-25 mm wide, on branched, spineless stalks.
Leaves alternate, lance-shaped, spiny-toothed, deeply pinnately lobed.
Cirsium foliosum - Elk Thistle or Leafy Thistle
Perennial, unbranched, leafy, 50-100 cm tall. Open areas, foothills-subalpine.
Flowerheads white to purple, 2-3 cm wide, densely clustered toward the top.
Leaves alternate, woolly-hairy, spiny-toothed, toothed to pinnately lobed.
Cirsium vulgare - Bull Thistle
Biennial, 30-150 cm tall. Stems branched, spiny-winged. Disturbed areas.
Flowerheads pink to purple, 3-5 cm wide, on branched, spiny stalks.
Leaves alternate, lance-shaped, hairy and spiny-toothed, deeply pinnately lobed.
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Contents English Names Index