Back to Target Weeds for Control
- Why should we care?
- This plant colonizes primarily in disturbed areas such as pastures, roadsides, and ditch banks, but also in hayfields and disturbed prairies. Because it is distasteful to most grazing animals, the bull thistle affects available forage. It generally does not pose a threat to high quality areas and does not withstand cultivation.
- How to Identify
- Biennial herbaceous plant, between 3–6 feet tall with one erect branched stem. It grows a rosette in its first year and blooms in its second year. The leaves are alternate, coarsely lobed, with each lobe having a spine at it’s tip. Spines extend downward from the leaves along prominent ridges of the stem. Upper leaf surface is rough. The flowers are disk-shaped flowerheads containing hundreds of tiny individual purple flowers which bloom from July through August. The roots consist of a fleshy taproot.
- About the Plant and Where it came from
- Circisum vulgare
- It was introduced to the U.S. in the early 1800s from Europe and Asia.
- The plant has numerous straw-colored seeds with plume-like bristles as dispersed by wind. They remain viable in the soil for over 10 years.
- How to Control
- Cultural control: Pulling or mowing in pulling or mowing in and dispose off-site to avoid reseeding.
- Chemical control: Spot-spraying with glyphosate, triclopyr or metsulfron when plants are in rosette stage (first year) in the fall wen non-target plants are less susceptible.
Biological control: Thistlehead-feeding weevil and rosette-feeding weevil. Caution: There have been observations of weevils feeding on native thistles.