Canada Thistle
Cirsium arvense (L.) Scop.
An introduced, erect, leafy and variable perennial up to 1.5 m tall that spreads by underground rhizomes forming clones. Stems are hollow and become hairy with age Leaves are alternate and without stalks and the base may clasp the stem. Leaves are deeply lobed with spines and the undersides are hairy. Plants are unisexual with 1 to 5 heads of pink-purple florets. Female flowers produce 50 or more light brown seeds attached to a feathery pappus for wind dispersal. Blooms in July and August.
Canada Thistle – Infestation
