Native to Europe, but now naturalized and found throughout most of North America.
A summer or winter annual or sometimes a biennial. Propagation is by seeds. Mature plants have a large taproot, and dead plants persist through the winter. If stems or foliage are broken they will exude a milky white sap.
Plants are common along roadsides and waste areas, as well as in landscape, crops, and poorly maintained turf. Thick stands of the plants may occur.
Mature plants have stalks resulting in large, open clusters of flowers, and these may be as tall as 6 feet, while the primary plant may be up to 4 feet tall. There usually is a single main stem, with branching only in the upper, flowering area. Stems are prickly in the lower half and sometimes smooth along the upper length.
Leaves are alternate and clasping, up to 10 inches long, with deep cavities between each lobe that are rounded toward the mid-vein of the leaf. Leaves have a rough feel to them, and they are prickly along the margins as well as on the mid-vein on the lower surface. This feature distinguishes this weed from sowthistle, which does not have the prickly mid-vein.
Flowers grow in large, open clusters at the ends of the many-branching stems. Flowers are yellow but may dry to a bluish color, and each flower head is composed of up to 14 flowers arranged ray or daisy-like.
Characteristicts Important to Control:
Annual weeds with a high seed production. Seeds are blown by the wind due to the feathery pappus attached to each seed.