Oklahoma State University
Oklahoma Invasive Species
Oklahoma State University

Purple Loosestrife
Lythrum salicaria

purple loosestrifepurple loosestrife
Country of Origin: Europe
History: Purple loosestrife was introduced in the U.S. and Canada in the 1800’s to use as an ornamental plant. Today it is still widely distributed as an ornamental plant.
Intended Use: None
Mode of Invasion:

It has spread through the U.S. at a rapid pace ever since it was brought here by ship ballast water and as a medical herb.  It has spread by roadway construction, ornament plants, and by commercial distribution. 

Species Description:

Purple loosestrife is a perennial with a square, woody stem and opposite or whorled leaves.  Leaves are lance-shaped and heart-shaped or rounded at the base.  These plants are usually covered by fine hairs or pubescence. Purple loosestrife plants grow from four to ten feet high, depending upon conditions, and produce a very showy colorful flower spike throughout much of the summer. Flowers have five to seven petals. Mature plants can have from 30 to 50 stems arising from a single rootstock.   It adapts readily to natural and disturbed wetlands. As it establishes and expands, it out competes and replaces native grasses and other flowering plants that provide a higher quality source of nutrition for wildlife. The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species and reduce habitat for waterfowl. 

Map of Occurrence:


Effects of Invasion: This plant changes the environment in many ways.  It alters the habitat for water fowl by changing their feeding habits.  It alters N-cycle and the water chemistry it is found in.  An invasion into a wetland can result in the reduction of native plant community and alteration of the wetland’s structure and function.  Large homogeneous stands of purple loosestrife can endanger various threatened and endangered native wetland plants and wildlife by eliminating natural foods and cover. Dense plant establishment’s has altered the flow of water. 

The control methods are dependent on the size of the population. Small populations can generally be controlled by digging the plants. Larger populations are usually controlled by foliar applications of herbicides.



LaFleur, A. 1996. Invasive plant information sheet: purple loosestrife. The Nature Conservancy, Connecticut Chapter.

The Nature Conservancy. Purple Loosestrife: element Stewardship Abstract. In: Wildland weeds Management & Research Program, Weeds on the Web.