This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual. Propagates by seeds.
Time of bloom: June to September.
Seed-time: July to October.
Range: Throughout North America except the far North.
Habitat: Fields, roadsides, waste places.
In Europe this plant is used as a pot herb, as its specific name, oleraceus, indicates, and is kept succulent by the constant pinching out of its buds. It springs from a white taproot, well fringed with feeding rootlets, the stem one to six feet tall, angled, branching, smooth, green, hollow between nodes, filled with milky juice. Leaves lyrate-pinnatifid, the terminal lobe large and triangular, the others narrow and decreasing in size toward the base; the lower and basal leaves petioled, but those on the stem clasping with an auricled and pointed base; the margins toothed with small, weak spines. Heads in crowded cymose panicles, yellow, nearly an inch broad; the involucres are downy while they enclose the buds, but later become smooth. Achenes brown, slightly flattened, with roughened ribs and thickly tufted, white, silken pappus. (Fig. 372.)
Fig. 371. - Field Sow Thistle (Sonchus arvensis). X 1/8.
Prevent seed development. In gardens and other small areas, hand-pull before the first flowers mature. Stubbles should have surface cultivation after harvest for the purpose of stirring into life such seeds as are on the ground, the seedlings to be turned under at fall plowing. Waste places and roadsides are too often permitted to mature seeds, to the damage of adjacent ground.