Canada thistle, also referred to as creeping thistle and California thistle, is a member of the Asteraceae or sunflower family. The plant is a herbaceous perennial that can grow up to 4 feet tall. Stems of the plant are erect, grooved, nearly smooth or hairy. Mature leaves are spiny with deeply lobed leaves and several branching flower stalks. Leaves are alternate, oblong, or lanceolate usually with crinkled edges and spiny-toothed margins that terminate in a spine. Leaves of the plant can be hairy or smooth. Canada thistle flowers can vary in color from pale blue to shades of purple with an occasional white ecotype. Variations in leaf and flower structures can be due to development of several ecotypes. Seeds of the plant are about 1/8 inch long, somewhat flattened, brownish, with a tuft of hair at the top.