Terrestrial invasive species

Nature

Most of these invasive plant factsheets are created from the booklet Minnesota invasive non-native terrestrial plants, an identification guide for resource managers.

Check the additional resources and herbicides table for more information.


Musk or nodding thistle (Carduus nutans)


 

Description:

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.

Ecological Threat:

  • It generally does not pose a threat to high quality areas. It colonizes primarily in disturbed areas.
  • Musk thistle is distasteful to grazing animals, giving the thistle a competitive edge.
  • It grows best in disturbed areas such as pastures, roadsides, and ditch banks, but also in hayfields and disturbed prairies.
  • A native of western Europe it was introduced to the U.S. in the early 1800s, and is declared an agricultural pest.
  • Musk thistle is not a MDA noxious weed on a statewide level although some counties may choose to list it as a county noxious weed.  Plumeless thistle is on the MDA Prohibited noxious weed (Controlled List) list in Minnesota.

 

Control Methods:

Mechanical
Pulling or mowing in early bud or bloom stage, then dispose offsite

Chemical
Spot-spraying with glyphosate, triclopyr or metsulfuron when plants are in rosette stage (first year) in the fall when non-target plants are less susceptible

Biological
Thistlehead-feeding weevil and rosette-feeding weevil. Caution: Observations of weevils feeding on native thistles

 

Native Substitutes:

Additional Resources