Alternate name: Bristle Thistle, Nodding Thistle, Nodding Plumeless-thistle
Family: Asteraceae, Aster view all from this family
Description Introduced, annual or biennial herb; invasive; highly variable; may form large colonies.
Habit: 1-7 upright branched, spiky, winged stems rise from a spiky basal rosette, up to 2 ft (.6 m) in diameter.
Height: 1.5-6.5 ft (.5-2 m) or more.
Leaf: in basal rosette, coarsely and sharply lobed, with sharp yellow to white spine at the lobe tips; waxy above, wooly below; to 10 in long by 4 in wide; on stem, smaller, less divided, ascending.
Flower: large, drooping, terminal globe or dome, rose to purple (rarely white), 1.5-3.5 in (38-90 cm) wide; atop spiky purple-brown cup.
Fruit: dry seed, straw colored, 3/16 in (5 mm) long; with bristles to 1 in (25 mm) long.
Flower May to October.
Habitat Neutral to acid soils in open areas: disturbed sites, waste ground, pastures, roadsides, fields, meadows, prairies, grassy balds.
Range Native to Eurasia; introduced to North America in ships' ballast in the early 1800s; now naturalized across southern Canada and in throughout the continental U.S. except for Maine, Vermont, Florida; to 10,000 ft (3000 m).
Discussion Also known as: nodding thistle, plumeless thistle, nodding plumeless thistle. Musk thistle is unpalatable to wildlife and livestock. This plant is considered weedy and invasive, and is listed as noxious in 24 states. Flower heads will droop to a 90-degree angle from the stem when mature, hence the alternate name, nodding thistle.