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Invasive Thistles

A close up of a thistle plant. The thistle has sharp spikes of green leaves. The flower is a light purple tuft.

Other names: Canada Thistle, Canadian thistle, Californian thistle, Creeping thistle, Field thistle, Corn thistle, Perennial thistle, Field thistle

Where did it come from?

Most invasive thistles came from Europe in the 1600s. The exact means of introduction are largely unknown, but it is speculated that they were brought over in farm seeds.

Why is it invasive?

Invasive thistles can decrease crop yields and reduce forage. These thistles also out compete native plants that animals rely on for food and shelter.

How do you prevent its spread?

Long term, consistent management can reduce the number of thistles and seeds in fields. In addition, checking field clothes and equipment for seeds before moving to a new area can reduce the spread of these plants.


Control Practices for Canada Thistle

Bull and Musk (Biennial) Thistle Control in Perennial Grass Crops

Species assessment spiny plumbless thistle

Species assessment musk thistle

Species assessment Canada thistle

Species assessment bull thistle

Native vs Invasive Thistles

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Image credit: Dennis Jarvis