Time of bloom: June to September.
Seed-time: August to November.
Range: New Jersey, Ohio, and the Middle Western States, southward to Florida, Texas, Arizona, and southern California. Naturalized throughout the Tropics in Asia, Australia, the South Sea Islands, and Africa.
Habitat: Fields, meadows, waste places.
In some countries this plant is cultivated for the valuable painter's oil expressed from its seeds, but in many parts of the United States it is a very troublesome weed, for, in addition to its exceeding prickliness, it is protected by bitter, yellow juices, said to be poisonous.
Stem one to two feet high, stout, simple or with few branches, usually very prickly but sometimes nearly or quite unarmed. Leaves four to eight inches long and half as wide, glaucous, blotched with white, sinuate-pinnatifid, spiny-toothed and more or less prickly on midrib and larger veins, sessile and clasping. Flowers lemon-yellow or cream-colored, two or three inches broad, sessile or on very short peduncles; sepals long and prickle-pointed; stamens many with filaments a half-inch or more long. Capsule an inch or more long, ellipsoid, prickly, opening by three to six valves at the top. Seeds small, grayish brown, crested on one side. (Fig. 118.)
Fig. 118. - Prickly Poppy (Argemone mexicana). X 1/5.
Prevent seed production. Pull, hoe-cut, or spud out autumn leaf-tufts; closely and frequently cut flowering stalks while in early bloom. Cultivation of the ground destroys the weed if continued for a sufficient time to stir all dormant seeds into growth.