Weed Control

Onopordum acanthium

Biennial

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Identification and management tips

• Scotch thistle is an imposing 8 ft tall plant with purple spiny flowers and 2 ft long leaves covered in woolly hairs.
• Scotch thistle is best controlled in the rosette stage the 1st year, either mechanically or chemically.
• If an existing seed source is dormant in the soil, re-treatments will be necessary for 4-6 years and are most effective when followed with revegetation.

Most effective control methods and timing

Prevention (Prev)  Monitor your land and destroy single plants before seed production to avoid costly expense.

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 out weed fact sheets for specific control information.

Links:

Fact Sheet (pdf 8kb)

Utah State University Ext. Weed Web: Weber County Weed Abatement (Chemical control)