Possibly introduced to North America as an ornamental, but so widely spread that it is not known for certain. Now present in all states except Hawaii, and throughout Canada north to Alaska.
A spreading summer annual that grows to over 3 feet in height, forming large and dense thickets of the plant. Plants typically grow in very wet soils along the edges of swamps, ponds, streams, or other wet areas. In “natural” areas it is a desirable plant, but it commonly invades irrigated croplands and irrigation or drainage ditches, impeding water flow.
Mature plants are typical of the smartweeds, with elongate, lance-shaped leaves attached to the stem without stalks. A papery sheath encloses the stem at the leaf junction, and at the top of this ochrea there is a fringe of stiff hairs. Leaves often have a purplish blotch in their center, and the lower surface often is dotted with tiny raised spots. Flowers occur in dense clusters of small pink flowers at the ends of the stems
Characteristicts Important to Control:
Reducing soil moisture is a critical factor in reducing conditions for growth of this weed. Mowing dense stands can reduce seed production, and the application of a contact or systemic herbicide will effectively kill the plants.