Wanted: Canada Thistle

Circium Avense

Where You May Find the Plant-

Canada thistle is an aggressive, creeping perennial weed that infests crops, pastures, rangeland, roadsides and noncrop areas. Generally, infestations start on disturbed ground, including ditch banks, overgrazed pastures, tilled fields or abandoned sites.


Flowers are purple-pink, in clusters one-half to three-quarters of an inch in diameter and bloom from June to October. Leaves are alternately arranged and lance-shaped to narrowly oval. Stems begin as a rosette and grow upright after two to four weeks.
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Why We Need to Take Attention-

Canada thistle poses an economic threat to the agriculture industry by reducing crop yields and outcompeting native plants.

Steps Being Taken to Control the Species-

  • Report infestations

  • Actively control noxious weeds on your property

  • Contact Clark County’s Vegetation Management Program for more information on species ID and recommended control methods

  • Spread the word about noxious weeds, and why controlling them is so important

  • Spread herbicides