Time of bloom: July to September.
Seed-time: Late August to October.
Range: New Brunswick to the Northwest Territory, southward to Tennessee, Louisiana, and Kansas. Habitat: Wet ground; low meadows, swamps, and along ditches.
In a report on "Fiber Investigations" made by the United States Department of Agriculture, it is stated that this plant yields a tough fiber, finer than that of hemp, soft, glossy, and possessed of great strength. Binder twine made of it stood a breaking test of ninety-five to a hundred and twenty-five pounds. It is a pity that the plant is not utilised so as to make valuable many a profitless swamp or marsh. Its hard, knotty roots are used in medicine, and are worth three or four cents a pound when collected in late autumn and carefully dried.
Stems slender, two to five feet tall, round, smooth, often reddish, sometimes simple but usually branching above, leafy to the summit. Leaves opposite, oblong-lance-shaped, smooth, long-pointed, usually obtuse at base, with rather short petioles. Flowers rosy purple, in flattened umbels, the pedicels finely hairy; the hoods of the crown erect and slim, the pointed horns within being as sharp as needles and longer than the hoods. Follicles slender, pointed at both ends, and held erect.
Drainage of the ground is the first step toward the destruction of Swamp Milkweed, after which it needs to be kept closely cut throughout the growing season in order to starve the perennial roots.