Asteraceae (Sunflower family)
Class B Noxious Weed
Control or Containment Required
Scotch thistle was brought to the U.S. as an ornamental in the late 1800s. It is now a widespread invader of roadsides, ditch banks, rangeland and pastures. It is a serious problem on rangeland where it reduces forage and limits land utilization for livestock and wildlife.
An upright, branched, robust biennial, Scotch thistle often grows more than 8 feet tall, covered with sharp spines and winged stems. It typically lives two years, its first year as a rosette with a taproot. The second year the plant bolts then flowers from June well into the fall months.
Scotch thistle reproduces by seed. Each plant can produce up to 40,000 seeds, which can remain viable in the soil up to 40 years.
Download our printable PDF with more information about Scotch thistle and best management practices for controlling it.
Like many noxious weeds, Scotch thistle attracts pollinators away from native plants. Note the "winged" stem, which is one way to identify Scotch from other thistles.
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