Genus: 1 species.
English: Waterwillow; Swamp loosestrife.
region: eastern United States, Canada.
Habitat: wetlands, swamps, shallow water, swampland, ditches, besides streams, edges of ponds and lakes.
BotanyClump-forming shrubby perennial, forming thickets.
Stems: arching, angular, smooth; woody near the base; 2.4 m tall; sometimes root at the tip.
Leaves: lanceolate; opposite or in whorls of three or four; 13 cm long and 25 m) wide; smooth above; hairy beneath; very short stalks.
Flowers: rose-pink; in axillary clusters; blooming in June and July.
Calyx:cup shaped.
Corolla: 2 cm wide; five petals, narrowing at the base.
Stamens: 10; projecting with five longer than the rest.
Gynoecium: one pistil, one style and a superior ovary.
Fruit: spherical dark brown capsule; numerous reddish seeds.