Musk Thistle, Nodding Thistle

(Carduus nutans L.)

Asteraceae (Sunflower Family)

▲ young seedling

▲ seedling

▲ early spring rosette in second year of growth-- about 2 foot diameter

▲ early flowering stage

▲ mature plant (about 6 feet tall) at full flowering in early May to early June in Springfield, MO

▲ leaf bases continue down stem

▲ wide, spiny bracts surround base of flower head

▲ large flower heads often 3-4 inches across (almost always over 2 inches across) and often bent or drooping to one side

 

Musk Thistle, Nodding Thistle, Milk Thistle  (pp. 124-125, Weeds of the Northeast; pp. 96-97, Weeds of the Great Plains)

• * a noxious weed in Missouri

• * very common in Southwest Missouri

• * large flower heads 2-3" across, tend to "nod"

• * blooms mostly in late spring

• * produces an average of 10,000 seeds/plant, but sometimes much more

• * biennial, dies after flowering

• * stems spiny, grooved

• * leaves shiny, almost waxy with spines along leaf edges

• * leaf bases extend partially down stem

• * can distinguish from tall thistle, bull thistle, scotch thistle and field thistle by the large, nodding flower head and lack of a lot of leaf  hairs (on most plants, except some northern U.S. popluations, which may have quite hairy leaves)

• * can distinguish from canada thistle by the presence of creeping roots and much small flower head on canada thistle

• * can distinguish from plumeless thistle by narrower bracts, smaller flowers and narrower leaves on plumeless thistle, compared to musk thistle; plumeless thistle often has more branched inflorescences than musk thistle

• * musk thistle weevil, a biological control agent, has been quite effective in a number of areas