Purple loosestrife [Lythrum salicaria L. (Lythraceae)] is a tall herbaceous perennial that may grow up to ten feet tall and four feet wide. Plants can reach maturity in three to five years, producing as many as 50 stems per plant. Leaves may be opposite, alternate or in whorls of three. The leaves are lance shaped and directly attached to stems. Stems are usually square, but may become five-or-six-sided and quite woody as plants mature. Leaves and stems of purple loosestrife may be smooth or covered with soft hairs. See pictures of emerging plants  below for earliest identification.

The woody roots form a dense mat underground, up to 20 inches in diameter. The tap root is a major source of carbohydrate for the plant that is used for regrowth when above-ground vegetation is mowed, suppressed by herbicides or damaged by insect feeding. The ability to rapidly send up new shoots gives purple loosestrife a competitive advantage over other plant species in disturbed habitats.

The length of the spike inflorescence ranges from one inch to more than three feet long, with up to 3,000 flowers produced on an individual plant. The reddish-purple flowers have five to seven petals. A single mature plant can produce as many as 2.5 million seeds each year. Purple loosestrife seeds are very small (1 mm.) and dust like, and are easily carried by wind or water. Seeds may also be moved about on animal fur or feathers or in mud on humans or other animals.

Donna R. Ellis, Program Specialist II, Department of Plant Science, U-67, University of Connecticut, Storrs, CT