Musk Thistle
Musk Thistle, Nodding Thistle
(Carduus nutans L.)
Asteraceae (Sunflower Family)
▲ young seedling
▲ seedling
▲ ▼ first year rosettes
▲ closer view of rosette leaves showing white hairs on edges that make the edges look wax-coated
▲ early spring rosette in second year of growth--about 2 foot diameter
▲ ▼ early flowering stage
▲ ▼ mature, flowering plants - top plant is about 6 feet tall, bottom plant is about 5 feet tall
▲ ▼ winged stems from leaf bases continuing 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
▲ pasture full of musk thistle near Springfield, MO
Carduus nutans L., Musk Thistle, Nodding Thistle, Milk Thistle: (Bayer Code: CRUNU; US Code CANU4)
- a noxious biennial weed common in Missouri
- first year rosette leaves appear somewhat shiny with "waxy" edges that appear whitish due to fine white hairs on leaf edges; leaf margins are toothed and spine-tipped
- sends up flowering stalk 2-8 feet tall by late spring and produces large flower head inflorescences that are 2-3 inches across and tend to "nod" or bend down
- heads have no ray flowers, and disk flowers are pink to purplish
- base of inflorescence is surrounded by bracts that are triangular and stand out from the head and end in a pointed tip
- flowering season is late spring to early summer (May-June), which differs from other invasive thistles (Canada thistle, bull thistle) that tend to bloom in mid to late summer (July-September)
- base of leaves on flowering stem extend down stem, producing spiny "wings" on stem
- produces an average of 10,000 seeds/plant, but sometimes much more
- biennial, dies after flowering
- stems are spiny, grooved
- 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 smaller, spineless 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
(Updated January 23, 2019)