Perennial sow thistle is common in cultivated areas, ditches, pastures, and undeveloped areas.
This weed is a tall, creeping perennial that reproduces by seed and horizontal, underground roots. The roots penetrate to a depth of 1.5 m to 3 m (5 ft. to 10 ft.). The stems are erect, hollow, 0.5 m to 1.2 m (2 ft. to 4 ft.) high, smooth, stout, and branch at the top. They produce a milky sap.
The leaves are alternate, have slightly-toothed margins, and are 15 cm to 30 cm (6 in. to 12 in.) long. The lower leaves have deeply-cut, backwards-pointed, side lobes. The upper leaves are slightly-toothed and smaller.
The flowers are bright yellow, dandelion-like, and 1.3 cm to 5 cm (1 in. to 2 in.) across. The seeds are brown, ridged, and wrinkled with a tuft of fine white hairs. Carried by the wind, the seed can establish itself in cultivated fields, roadsides, on the margins of sloughs, and along shelterbelts. It prefers moist, fertile soils.