Widely spread across Utah. Control efforts focus on reducing or eliminating new or expanding populations.
Quick Facts
Report your sighting through EDDMapS to help us track and respond to new infestations.
Report on EDDMapSScotch Thistle (Cotton Thistle)
Onopordum acanthium
Overview
Scotch thistle is one of the largest thistles in the world, reaching up to 9 feet tall. It is a biennial plant from Eurasia that invades rangelands, roadsides, and disturbed areas. Its large size and dense spines make it impenetrable to livestock and wildlife.
How to Identify
Biennial up to 9 feet tall. Very large, deeply lobed, spiny leaves covered in white woolly hairs. Continuous spiny wings along the stem. Purple flower heads 1-2 inches across.
Control Methods
Hand-pull or cut rosettes below the soil surface before flowering. Herbicide treatment on rosettes in fall or spring.
Herbicide Recommendations
Clopyralid, picloram, or 2,4-D applied to rosettes. Fall treatment is most effective.
⚠️ Always read and follow pesticide label directions. Contact your county weed superintendent for site-specific recommendations. Permits may be required near water.
Need help managing this weed?
Skyline CWMA can connect you with technical assistance, cost-share programs, and licensed contractors for treatment on your property.
