Canada Thistle (Cirsum arvense)
Description: A herbaceous perennial in the aster family, 2'-5' in height. Forms dense stands that choke out other vegetation.
Life cycle: Perennial with creeping roots
Habitat: Grows in barrens, glades, meadows, fields, pastures, and waste places. It does best in disturbed upland areas but also invades wet areas with fluctuating water levels such as stream banks. It can also be found in clay to gravely soils.
Leaves: 3-8 inches long, alternate with spiny, crinkled margins; lower leaves are lobed.
Stem: Grooved and hairy with age, not spiny, branched at apex.
Flower: Lavender flowers, 3/4 - 1" in diameter.
Fruit: Numerous small seeds attached to brown feathery "pappus" that spreads the seeds by wind dispersal.
Root: Creeping root system allows this weed to spread aggressively. Hand-pulling and cultivation are often ineffective control mechanisms because new plants sprout from root pieces that snap off.
The problem is….Canada thistle is a highly invasive thistle that competes aggressively with other plant species through shading, competition for soil resources, and possibly through the release of chemical toxins poisonous to other plants.
