Credit: Richard Gardner, Bugwood.org
General Information
Species Name: Lythrum salicaria
Also Known As: bouquet violet, rainbow weed, spiked loosestrife, salicaire, bouquet violet
Family: Lythraceae (Loosestrife)
Growth Form: Forb
Life Span: Perennial
Flowering Dates: July-October
Origin: Eurasia
Noxious: Yes. Purple loosestrife is listed as a State Noxious Weed under the Noxious Weed Control Act in Nebraska, which means it is required by law for it to be removed from public and private land in the state.
Category 4: Noxious Aquatic Invasive Species
Why Is It Invasive?
Purple loosestrife is competitive and can rapidly displace native species if allowed to establish. Once established, the prolific seed production and dense canopy of purple loosestrife suppresses growth and regeneration of native plant communities. Monotypic stands of purple loosestrife may inhibit nesting by native waterfowl and other birds. Other aquatic wildlife, such as amphibians and turtles, may be similarly affected. The dense roots and stems trap sediments, raising the water table and reducing open waterways, which in turn may diminish the value of managed wetlands and impede water flow.
What Does It Look Like?
General Characteristics
Purple loosestrife is a tall, multistemmed (30-50 per plant) wetland plant that can grow up to 10 ft. (3 m) in height. It has showy purple flowers arranged on flower spikes. Purple loosestrife produces thick, woody roots. On mature plants, roots are extensive and can send out 30 to 50 shoots, creating a dense web. Pieces of the roots and stem fragments can also produce new plants.
Flowers
Individual flowers have five or six pink-purple petals surrounding small, yellow centers. Single flowers make up flower spikes, which can be up to one foot tall.
Leaves
Leaves are lance-shaped with smooth edges and grow up to four inches long. They are usually arranged in pairs opposite each other on the stem, and rotated 90 degrees from the pair below. Leaves sometimes appear whorled (radiating out from a single point) around the stem.
Stems
A recognizable feature is the square-shaped stem, which is generally four to six-sided. A single plant is made up of multiple woody stems.
Seeds
Purple loosestrife spreads primarily by seeds. When flowers drop off, capsules containing many tiny seeds appear in their place. Each mature plant can produce up to 2.7 million seeds annually. As tiny as grains of sand, seeds are easily spread by water, wind, wildlife and humans. Germination can occur the following season, but seeds can also lay dormant for several years before sprouting.
Photos
Where Does It Grow?
Purple loosestrife currently infests ~8,000 acres in Nebraska. While wetlands, marshes, stream and river banks tend to carry the largest infestation levels, sub-irrigated hay meadows, recreational lakes and irrigation canals are equally threatened.
How Does It Spread?
The species was unintentionally introduced to the United States’ Great Lakes through contaminated solid cargo ship ballast as well as through the deliberate importation of seeds. The first discovery in the United States was in Lake Ontario in 1869. Purple loosestrife was sold and planted for decades as a decorative ornamental plant. However, due to its negative impacts on native plants and its ability to escape from cultivation, purple loosestrife is illegal to sell in most states.
How Do I Control It?
Management of invasive aquatic plants involving either mechanical removal of plants or application of herbicides to public waters requires a permit. Contact the Contact the Nebraska Game and Parks Commission for more information.
A combination of two or more control methods is the best approach to take when controlling purple loosestrife. By utilizing several control options, your odds become better that more of the targeted plant will be controlled. Purple loosestrife is capable of producing millions of seeds that may lay dormant for many years. Continued monitoring and follow-up control measures are essential for maintaining purple loosestrife infestations at a low level.
Mechanical
Small infestations can be dug or pulled by hand taking care to remove as much of the root mass as possible. Plants should be placed in a dry area that is not subject to flooding or water runoff. Dried plants can be burned or buried in an approved landfill. It is necessary to monitor controlled areas for regrowth from roots or seeds. Mature plants are capable of producing over 2 million seeds. Mowing is not recommended since this creates many small pieces of plant that can re-vegetate. Purple loosestrife will primarily be located in wetlands, marshes or on the edge of bodies of water. It is usually not located in dry areas, but has been documented several hundred feet from a wet area.
Purple loosestrife is usually not associated with agricultural crops but has been reported to grow in sub-irrigated hay meadows and pastures. It can also infest irrigation canals which in turn could become established in crop ground.
If you are on public land or unsure of which method(s) would work best on your private land, contact the Nebraska Game and Parks Commission or your local county weed control authority to determine appropriate removal methods.
Biological
The use of natural enemies (biocontrol agents) for the control of purple loosestrife is currently being studied in Nebraska. These agents work slowly, and favorable results may not be seen for many years. Biocontrol agents are considered a tool to assist in control and should never be relied on to completely control any noxious weed. To be deemed acceptable, this method of control shall be as effective as the use of herbicides and shall be approved by your local county weed control authority.
Cultural
CLEAN your watercraft, trailer, angling gear and other equipment. Remove all aquatic vegetation and animal species from your equipment.
DRAIN your watercraft at the ramp by removing the boat plug and draining all live wells and ballast tanks.
DRY your watercraft, trailer and other equipment for at least 7 days before visiting another waterbody. If coming from a known zebra mussel infested waterbody, allow your watercraft and equipment to dry for at least 30 days before using them on an un-infested waterbody.
DON'T LET IT LOOSE. Do not release or transport exotic or non-native fish species to new ecosystems, and do not dump aquariums. It is unlawful to release any aquatic species into a waterbody other than the one from which it was harvested. Doing so can promote the spread of AIS.
Chemical
Application of chemicals to public waters requires a permit. Contact the Nebraska Game and Parks Commission for more information.
For chemical control on private land and/or waters, please refer to the 2025 Guide for Weed, Disease and Insect Management in Nebraska or contact your local county weed control authority.
What Should I Do If I See It in Nebraska?
If you see purple loosestrife in Nebraska, you should report it to the Nebraska Game and Parks Commission's Aquatic Invasive Species (AIS) Program using their AIS Report Form. For guidance on what information to include in your report, check out our reporting tips.
References and More Information
California Invasive Plant Council
Center for Aquatic and Invasive Plants
Center for Invasive Species and Ecosystem Health
Connecticut Invasive Plant Working Group
Maine Department of Agriculture, Conservation, & Forestry
Minnesota Department of Natural Resources
National Invasive Species Information Center
Nebraska Department of Agriculture
Nebraska Game and Parks Commission
Nebraska Weed Control Association
New York Invasive Species Information
North Carolina Extension Gardener Plant Toolbox
USGS Nonindigenous Aquatic Species