Purple Loosestrife

 Purple lythrum, bouquet-viole, spiked loosestrife 

Purple loosestrife is a perennial that can grow up to 10 feet in height and typically prefers moist or riparian habitat. Due to the numerous four-sided stems that are green to purple in appearance, this plant appears woody and bush like in appearance. Clasping leaves have smooth margins, are lance shaped, and are heart-shaped or rounded at the base. Purple loosestrife leaves and stems are covered by downy fine hairs, and leaves are whorled or alternate on the stem. In autumn with dehydration, the leaves turn red. The showy purple to magenta colored flowers is clustered on a long spike that can extend 2 inches to 3 feet down the stem called a raceme. Each flower has 5 to 7 petals and blooms from June to September. Seeds burst at maturity around late July or early August and each stem can produce up to 3 million tiny seeds per year. This plant has a dense, woody, and extensive root system with the root system and the seed production result in a rapid spread of loosestrife. When a stem of the plant is broken off or disturbed it will start growing new shoots. 

The square or octagonal stems, the red leaves if the plant gets dried out in the fall and long clusters of showy purple to rose colored flowers. 

Moisture is required for growth and reproduction, but well established plants can persist on dry sites. Purple loosestrife is suited to seasonal wetlands and is capable of invading wet meadows, river and stream banks, pond edges, reservoirs, ditches, irrigation canals and marshes. 

There are herbicides and other control methods that commonly control purple loosestrife. Aquatic labeled herbicides would generally be necessary for use on purple loosestrife due to its affinity for growing in wet areas. Aquatic glyphosate, 2,4-D, and triclopyr are effective for control. Hand pulling and digging may also be effective but difficult. For more information on these herbicides and other control methods contact the Weed and Pest office. 

In the past, this plant was used as a medicinal herb for treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores. Was brought from Europe in the 1800’s as a garden perennial and still today it is sold as an ornamental.