Time of bloom: June to September. Seed-time: July until cut off by frost. Range: Throughout North America except the extreme North. Habitat: Fields and waste places; invades most crops.
Not very troublesome in ground requiring close tillage, but a special nuisance ingrain fields; climbing over and strangling the rightful growth, robbing it of food and moisture, bending it down by weight of its own fruitage. The seeds have long vitality and begin to ripen and drop into the soil before harvest; are gathered with the grain and often distributed with it; often fed to cattle in screenings from the mills, and returned to the soil in stable refuse or in droppings.
Stem slightly angular, roughish, branching, one to three feet long. Leaves halberd-shaped or long-pointed, heart-shaped, smooth, dark green, with slender petioles usually not so long as the blades. Flowers in slim, interrupted, axillary racemes, or often in small clusters of two to six on the small branches; they are greenish white, the calyx five-parted, persistent, enfolding the achene, which is black, pointed, three-angled, resembling a small kernel of buckwheat. (Fig. 62.)
Fig. 62. -Black Bindweed (Polygonum Convolvulus). X 1/4.
Sow clean seed. Before they begin to twine, rake the Bindweed seedlings from the young grain with a weeding harrow. Directly after harvest induce germination of seeds on the ground by giving surface cultivation, the resulting growth being winter-killed or turned under by the plow. Put the ground to a cultivated crop before using it again for grain.