Link to the WSNWCB Home Page link to the About Us page Link to the Weed Laws page Link to the Noxious Weed List Link to the Weed Information page link to the Frequently Asked Questions page Link to the Education page Connect to other Links page Link to Contact Us page Link to employment opportunities page

Class B Noxious Weed

Purple Loosestrife
Lythrum salicaria

 

Purple loosestrife flower


Plant family: Lythraceae
Year listed: 1997
Native to: Eurasia

Why is it a noxious weed?
Purple loosestrife is a vigorous competitor and can crowd other vegetation including native species. In a short period of time it will completely dominate a site. It can quickly adapt to environmental changes and expand its range to replace native plants used for ground cover, food or nesting material. Loosestrife stands are dense at the top, and open at the base, providing no cover for waterfowl.

 

How would I identify it?
General Description: Purple loosestrife is an emergent aquatic plant. It can reach up to 10 feet wide and 5 feet wide from a persistent perennial tap root and spreading rootstock.

Leaves:

  • 1 ½ to 4 inches long
  • wider and rounded or heart-shaped at the base
  • shape varies from lanceolate to narrowly oblong
  • sometimes covered with fine hairs

 

Flowers:

  • showy
  • magenta
  • 4-16 inch flowering spike

Stems:

  • herbaceous, erect
  • plant will have 30 - 50 stems
  • flowers form at ends

How does it reproduce?
Purple loosestrife reproduces by seed and vegetatively. A mature plant can produce 2.7 million thin-walled, flat seeds.

Where does it grow?
Purple loosestrife occurs in freshwater and brackish wetlands.

What is the distribution in Washington State?

 

 

 

Click on map to enlarge.
  • Purple loosestrife has been documented throughout Washington.
  • Refer to map for distribution levels in specific counties. If you think you may have seen this weed, please contact your county weed coordinator or us at noxiousweeds@agr.wa.gov.

 

  • Distribution map is based on 2003 data.

How do I control it?

General control methods:

Cultural: Cutting alone is not a control option for purple loosestrife. Shoots and adventitious roots will
develop.

Herbicide: Because herbicide availability and regulation differ between States, as well as between countries, we recommend the Washington Department of Ecology web site for information on aquatic weed management and herbicides.

Mechanical: Information not available at this time.

Biological: Galerucella calmariensis and G. pusilla - both leaf-feeding chrysomelids defoliate and attack the terminal bud area, drastically reducing seed production. Hylobius transversovittatus - root-mining weevil that also eats leaves. Nanophyes marmoratus - a seed eating beetle. N. brevis - a seed eating beetle.

Are there plants that may be confused with Purple loosestrife?
Native Spirea (Spirea douglasii) and Fireweed (Epilobium augustifolium) look similar to Purple loosestrife. If you need help with plant identification, please contact  your county noxious weed coordinator.

 

For more information
For more information, download our Written Findings.

View the Garden Wise Eastern Washington and Western Washington Guides for better noninvasive plant recommendations for your yard or garden.

More Photos-Click photo to enlarge
Feel free to download, or contact us to receive high-resolution JPEG or TIFF formats
purple loosetrife infestation wetland infestation purple loosestrife plant
Purple loosestrife infestation. Purple loosestrife wetland infestation. Purple loosestrife plant.

 Last updated August 26, 2008