Out in the Weeds With Ecological Services - Musk Thistle

• Biennial, reproduces by seed

• Plants are 2 to 6 feet tall

• Leaves are dark green, deeply lobed, with spines on edges. Leaf midribs may be whiteish

• Flowers are large, disk shaped, pink to purple, and solitary at the end of branches

• Distinct bracts are pinecone-like and prickly

• Flower heads will droop (or nod) when mature

Negative Impacts

• Unpalatable to livestock and wildlife

• Can dramatically reduce agricultural yields

• Able to spread quickly and crowd out native vegetation

Management Strategies

• Preventing seed production of this biennial species is critical. Rosettes can be easily dug to control small populations. Take care to protect yourself from the sharp spines on the leaves

• The Palisade Insectary has a Request-A-Bug program for a biological control agent for musk thistle. For more information on musk thistle biological control, visit the Musk Thistle Biocontrol Page

• For a list of suggested herbicide active ingredients for musk thistle, please refer to the 2025 CSU Herbicide Recommendations.

For more information regarding musk thistle and its management, visit the CSU musk thistle fact sheet.