Appearance: Biennial herbaceous plant, between 1 1/2 - 6' tall, multi-branched stem. Plants overwinter in the rosette stage.
Leaves: Alternate, coarsely lobed, dark green with light green midrib, smooth and hairless. Large first year rosette leaves.
Flowers: Disk-shaped flowerheads contain hundreds of tiny individual purple flowers which bloom from June through July. Flowerheads droop to a 90 degree angle from the stem when mature.
Roots: Each plant has a fibrous taproot.
Plumeless Thistle - Carduus acanthoides (no picture) is very similar especially in rosette stage, hybridizes readily with above; flowers are one-third the size of above and not nodding, underside of leaf is hairy.
- Musk Thistle Fact Sheet (MDA)
- Minnesota Noxious Weeds (MN DOT)
- US Forest Service Fact Sheet
- University of Minnesota Extension
- Plant Conservation Alliance Fact Sheet
- Invasive and Native Thistle Identification (South Dakota State University)