Purple Loosestrife Control in Washington State

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Purple Loosestrife Control in Washington State

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picture of a patch of purple loosestrife

The Washington State Department of Agriculture (WSDA) works with county, state and federal programs throughout the state to help coordinate research and control efforts on purple loosestrife (Lythrum salicaria). Purple loosestrife is listed as a class B noxious weed. According to our state noxious weed laws, landowner control is required in some areas. Please contact your county noxious weed program for specific control requirements in your area.

Purple loosestrife is also a quarantine species.  According to the Lythrum quarantine (WAC 16.752.400-415), it is illegal to transport, buy, sell, offer to sell or to distribute plants, plant parts or seeds of purple loosestrife into or within the state of Washington.  The Lythrum quarantine applies to all Lythrum species, including any hybrid cross and all named cultivars.WSDA and the county noxious weed control programs do realize this semi-aquatic weed is found in almost every county in Washington State. It flourishes in some areas, making control difficult if not impossible. In these sites, a long term control plan is the goal. WSDA follows the principles outlined in Integrated Pest Management (IPM), and guidelines for purple loosestrife control are found in the State IPM Plan on the Department of Ecology web site.Washington State has a long history of working together with county, state and federal weed control programs to control this invasive non-native weed - and this work continues.


Background and History, Reports

  • Purple Loosestrife Control Efforts:  A Ten Year Perspective 1991
  • Purple Loosestrife:  Report to the Legislature on the 1991 Control Program
  • Legislative Reports (199819992000)
  • Purple Loosestrife Biological Control History in Washington State  2000, 2008 update

Education and Outreach



Laws and Rules

The following web sites provide information on the laws and regulations regarding purple loosestrife control in Washington State.  The Washington State Noxious Weed Control Board provides an overview of these rules and regulations.

WSDA maintains and regulates a plant quarantine list, called Plants and Seeds Whose Sales are Prohibited in Washington State. This quarantine identifies plants known to be invasive and a threat to the state's economy and natural resources.  These regulations serve to prevent the introduction of these problem plants into Washington.

There are three major categories of quarantined plants:

Links to Related Sites