Douglas County Weed Management

Welcome to the Douglas County Weed Management Website.


The Pacific Northwest Weed Management Handbook, "Control of Problem Weeds" page has been updated!  This website give information regarding specific weeds that may be troublesome to control. Herbicides and/or rates listed cannot necessarily be used on cropland. Rates of application and restrictions vary depending on crop or site. Do not apply to a crop or site not listed on the label.

Control of Problem Weeds

In October 2004, Douglas County Commissioners activated the Douglas County Weed Management Task Force and appointed nine individuals who geographically represent Douglas County agriculture and urban areas. Margaret Viebrock, WSU Extension, was appointed to facilitate this committee and help to develop weed management strategies.

Ex-officio members of this Task Force include representatives from Douglas County Transportation and Land Services, Foster Creek Conservation District, Douglas County Commissioners and WSU Extension.

Task Force Directives (defined by the Douglas County Commissioners)

  • Develop a communication system with all entities that have weed control programs.
  • Gain a better understanding of weed control methods used by other other entities.
  • Design a system to coordinate weed control efforts.
  • Continue the process of developing an informed educational approach to weed management in Douglas County.
  • Engage landowners and agencies in a cooperative weed management program.


Since the appointment of the Douglas County Weed Management Task Force, the committee has taken a proactive approach to learn about various weed management programs. Members have met with agency people, integrated weed management program managers, state weed board representatives, county noxious weed control managers and other groups who manage weeds. The best parts of these programs have been integrated into the local plan of work. Members have also spent time in Olympia with state legislative groups explaining how the program has been successful in Douglas County.


Canada Thistle

Canada Thistle 1

Canada Thistle 2

Canada Thistle 3

Canada Thistle Facts

  • Douglas County Class C weed.
  • Native to southeastern Eurasia. It is believed to have entered the U.S. as a contaminate of crop seed as early as the 18th century.
  • Usually grows 1 to 4 feet tall.
  • Leaf margins are made up spiny-tipped irregular lobes.
  • Flowers: white to purple and borne in clusters of 1-5 per branch.
  • Flowering occurs during June to October.
  • Plants can produce up to 5,200 seeds annually but average about 1,500. Most seeds do not remain viable after 3 years.
  • Canada thistle can also spread vegitatively from horizontal roots that give rise to new shoots.
  • Canada thistle is adapted to a wide range of soil types and environmental conditions. It can be found infesting crops, pastures, rangelands, roadsides, and riparian areas.
  • Other names: Field thistle, California thistle
  • Control Methods:

Prevention:  Prevent establishment by eliminating new seedlings before they form a well-developed root system. Reduce the spread of Canada thistle by always purchasing certified seed.

Biological: There are several insects that have been released as biological control agents for Canada thistle. 

Mechanical: Repeated mowing can be effective in reducing seed-set. Intensive cultivation (multiple operations) aimed at depleting the food reserves in the roots, followed by competitive cropping, is effective in the long term.

Chemical: Contact your local chemical provider or Extension office for herbicide recommendations.

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