Perennial by deep roots and creeping rootstocks. Stems: leafy below, panicnlately branched and nearly naked above. Leaves: lower and basal runcinate-pinnatifid, spinulose-dentate. Flowers: heads several, corymbose-paniculate, bright yellow, very showy. Fruit: achenes oblong, compressed, with about ten rugose longitudinal ribs. Not indigenous.

Every traveller will easily recognize this common Sow Thistle, with its yellow or yellowish flowers and its very prickly leaves. Sometimes it is called Milk Thistle, on account of the milky juices contained in the stems. Like many of the members of the great family of Composites, the Sow Thistle has an involucre of green bracts, a flat naked receptacle, and numerous strap-shaped rays, which are truncate and finely toothed. It is a coarse showy weed, and opens its flowers early in the day, closing them again soon after noon. This is an introduced plant.