Mature Plant

Description: Purple loosestrife is an aquatic perennial that reproduces by seed, underground roots, and can spread by sprouting from pieces broken off the plant. It has a woody taproot with a fibrous root system that forms a dense mat. The erect stems of a mature plant can reach 7 feet. The stems are somewhat square, covered with fine hairs, and branched. The leaves are opposite or whorled, linear shaped with smooth edges, hairy, and attached directly to the stem. The flowers are in dense terminal spikes at the top of the plant. Flowers are purple-magenta with 5 to 7 petals. Flowering begins in June and continues through early September. The seeds are produced in seed pods that contain many seeds. The seeds are flat, light tan to golden brown, and very tiny (400 x 200 microns), about the size of a tip of a pin. Each plant can produce 120,000 to 2.7 million seeds in a single growing season.

Seed

Distribution: Purple loosestrife is an aquatic plant that grows in wet soils in wet meadows, pasture wetlands, cattail marshes, streams and river banks, lake shores and ditches. Purple loosestrife infestations are increasing in Minnesota. Currently, purple loosestrife has been identified in more than 75 percent of Minnesota's counties.