Mexico. Habitat: Cultivated crops, meadows, and waste places.
A native of tropical America now very common in the rich bottom lands of the Southern Seaboard and Gulf States. Stems one to three feet tall, smooth, diffusely branched from the base, spreading wider than its height. Leaves one to three inches long, opposite, ovate or sometimes heart-shaped, rather thick in texture, with slender petioles, scalloped or wavy edges, and whitened under-surface specked with minute black dots. Flowers very small, scarcely a twelfth of an inch broad, in clusters of two to six on very slender peduncles; calyx, funnel-shaped, five-ribbed and five-lobed, white or purple; stamens five or fewer, exserted. The single seed is about an eighth of an inch long, shaped like a reversed pyramid, the sides strongly five-ridged, the top flat. When in the soil the seed retains its vitality for several years. (Fig. 85.)
Fig. 85. - Hog-weed (Boerhaavia erecta). X 1/4.
In cultivated ground, very thorough and continued tillage in order to prevent the distribution of late-maturing seeds. In meadows the hay should be harvested while the weed is in its first bloom, with repeated cuttings as the plants recover. But rankly infested fields require to be put under cultivation, which should be followed by heavy seeding with clover.