Pest Profile

Canada Thistle
Cirsium arvense

Pest Description

Taken from State of Kansas:


Introduced perennial that reproduces by seeds and whitish, creeping rootstocks which send up new shoots every 8 to 12 inches. Plants 2 to 4 feet tall, branched above, with a well-developed, freely branching, fibrous root system. Leaves alternate, simple, oblong or lanceolate, irregularly lobed and spiny toothed, hairy when young, dark green. Flowers white or rose-purple in composite heads grouped at ends of top branches. They are usually dioecious, i.e. male and female flowers on different plants. For viable seed to be produced both male and female plants need to be present. Seeds about 1/8 inch long, smooth, light to dark brown color, oblong, slightly flattened and slightly curved, bear a white hairy pappus (parachute) at the top which helps support the seed in the air.

Pest photo source

Dr. Dallas Peterson, KSU