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.

Bull thistle (Cirsium vulgare)



Description:

Appearance: Biennial herbaceous plant, between 3 - 6' tall with one erect branched stem. It grows a rosette in its first year and blooms in its second year.

Leaves: Alternate, coarsely lobed, each lobe with a spine at its tip. Spines extend downward from the leaves along prominent ridges of the stem. Upper leaf surface is rough.

Flowers: Disk-shaped flowerheads contain hundreds of tiny individual purple flowers which bloom from July through August.

Seeds: Numerous straw-colored seeds with plume-like bristles are dispersed by wind. They remain viable in the soil for over 10 years.

Roots: Each plant has a fleshy taproot.

Ecological Threat:

  • It colonizes primarily in disturbed areas such as pastures, roadsides, and ditch banks, but also in hayfields and disturbed prairies.
  • Bull thistle is distasteful to most grazing animals, giving the thistle a competitive edge.
  • It generally does not pose a threat to high quality areas. Does not withstand cultivation.
  • It was introduced to the U.S. in the early 1800s from Europe and Asia.

Control Methods:

Mechanical

Pulling or mowing in Pulling or mowing in and dispose off-site to avoid reseeding

 

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: There have been observations of weevils feeding on native thistles

 


Native Substitutes:

Additional Resources