Weed Control
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Musk Thistle
Information | Images
Carduus nutans
Biennial
Identification and management tips
- Musk thistle flowers are large reddish-purple and "nod" at maturity.
- It is classified as a biennial, although it often germinates in late summer, it over winters as a rosette, and produces flowers and seeds the following summer.
- Musk thistle is a prolific seed producer. One plant can set up to 20,000 seeds. However, only one-third of the seeds are viable.
- The key to successful musk thistle control is to prevent seed production.
- For small infestations, the most effective control is digging up the rosettes in the spring.
- Musk thistle will not tolerate tillage and can be removed easily by severing its root below ground with a shovel or hoe.
- For large infestations, herbicides such as Tordon, Vanquish/Clarity or 2,4-D can be applied to musk thistle rosettes in spring or in the fall after new rosettes emerge. Apply Ally or Telar up to the early flower growth stage.
- However, as with all weed control, an integrated approach is best. Musk thistle's tolerance to most herbicides increases after it bolts, and therefore herbicides should be applied selectively and only at the most appropriate time.
Most effective control methods and timing
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Prevention (Prev) Monitor and destroy new plants before seed production.
Mechanical (Mech) Hand pulling, digging, cutting, mowing and tilling.
Cultural (Cult) Biological control agents, livestock grazing, and revegetation practices.
Chemical (Chem) Selective herbicides based on the plant and the specific location. Check our weed fact sheets for specific control information.
Links
Photo credits
Left to right:
- Steve Dewey, USU (left 2);
- Jim Gores, Teton County Weed and Pest