An herblike perennial growing usually in swamps or shallow water. Although appearing like an herbaceous plant it is more or less shrubby. The stems are angular, recurved, smooth and somewhat woody below, 3 to 10 feet long, often rooting at the tip when they reach the soil or mud. Leaves lanceolate, opposite or verticillate, 2 to 5 inches long, one-third to I inch wide, smooth above, somewhat hairy beneath, pointed at both ends, on very short petioles. Flowers numerous in cymelike axillary clusters; calyx broadly campanulate; corolla about an inch or less broad, petals cuneate at the base, pink-purple, the slender filaments of the stamens projecting from the flower. Fruiting capsule about one-fourth of an inch in diameter or slightly less.
Memoir 15 N. Y. State Museum
A. swamp loosestrife; willow-herb Decodon verticillatus
In swamps, shallow water around the edges of lakes and ponds, or along slow streams, often forming thickets, Maine to Florida, west to Minnesota, Tennessee and Louisiana. Flowering in June and July. Also known as peatweed or slink-weed, wild oleander and grass poly.