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Weeds and WeedMapper

  • Are noxious weeds considered noxious or invasive in their host countries?For the most part, no. These plants have existed for centuries in their host county, but their populations have been kept to manageable levels naturally by other plant competition, insects, pathogens and a host of other predators. When plant populations in these countries of origin increase, insects and other predators increase accordingly to help keep them in check.
  • Has there been a resurgence of tansy ragwort in the Willamette Valley?Tansy does best when a winter drought was followed by a warm wet spring, which creates the conditions for seed germination. Tansy in Western Oregon is targeted for biocontrol and eradication in Eastern Oregon. Tansy has made a big comeback in some parts of the Willamette Valley. Tansy thrives where grazing, logging, or fire disproportionately restrict native plants. Tansy is often a symptom of overgrazing or rodent tillage opening room for seed bank germination.Seeds can still form if treatment is conducted during full bloom, wasting time and money. Treatments before bolting are best.
  • How can I apply for a Noxious Weed Control Program grant?Competitive grant funding is available for on-the-ground weed control projects through the Oregon State Weed Board, and must be for state listed noxious weeds. Each year online applications open in October, are due in December, and are awarded the following February.
  • How can I get my neighbors to control their weeds?Try talking to your neighbors first to explain the importance of controlling weeds and share information from our noxious weed profiles with them to help explain the problem. If that is not helpful, you can check with your local government entities about codes or regulations that mandate weed control. Homeowner associations may also require members to control noxious weeds. Local Soil and Water Conservation Districts and Watershed Councils can be great resources to help educate neighbors and can sometimes provide control assistance as well. Property owners are required by law to report any Oregon “A”-listed noxious weed within 48 hours. ODA will work closely with them on developing a plan that they are comfortable with to control the “A” listed weeds, and can offer assistance at no cost.
  • How did noxious weeds get here and where did they come from?Most of Oregon’s least desirable weeds are of Mediterranean, European, and Asian origin. The introduction of non-native invasive plants has increased dramatically in the past decade because of the increased ease and speed of world travel and the expansion of global commerce. Local spread of noxious weeds can be natural by wind, water, and animals; but human activities such as, recreation, vehicle travel, and the movement of contaminated equipment, products, and livestock often greatly increase the distance and rate of dispersal.
  • How do I find out whether a plant I am selling is a noxious weed?Review the Noxious Weed Control Program’s state noxious weed list and program site. Noxious weed lists for other states can be found on the National Plant Board Laws and Regulations website.
  • Is butterfly bush a listed noxious weed?Yes, except for specific approved varieties listed on ODA’s Nursery Program page. If you planted your butterfly bush before it was listed (2004), you do not have remove it, but it is advisable to deadhead the plants after blooming to prevent the seeds from spreading whenever possible. Better yet, replace your butterfly bush with some native or non-invasive plants. Your local nurseries can help you choose a range of shrubs to replace your butterfly bush.
  • What is a noxious weed?A plant designated by a governmental agency to be injurious to public health, agriculture, recreation, wildlife, or property, or specifically in Oregon: “a terrestrial, aquatic or marine plant designated by the State Weed Board…as among those representing the greatest public menace and as a top priority for action by weed control programs. (ORS 569.175)” Most noxious weeds are non-native plants that are serious pests causing economic loss and harm to the environment. Noxious weeds choke out crops, destroy range and pasture lands, clog waterways, affect human and animal health, and threaten native plant communities. ODA staff complete risk assessments on plants that are potential threats, then present the findings to the Oregon State Weed Board, which votes whether or not to add them to the noxious weed list.
  • What is an NPDES permit and do I need it?The Oregon Department of Environmental Quality (DEQ) has a Clean Water Act permit requirement for certain pesticide applications, in, over, or near waters of the state. A National Pollutant Discharge Elimination System (NPDES) pesticide general permit is required by a federal court order and is implemented in Oregon by the DEQ under an agreement with the EPA.
  • Where can I find the weed distribution in the state?ODA's Weedmapper is a tool that allows you to access mapped noxious weed distribution in the state. Follow the simple user guide see weed profiles and locations.
  • Whom do I call with noxious weed control questions?Local ODA Noxious Weed Control specilists are experts in integrated weed management and are familiar to the counties and areas in which they serve. Additionally, there are other agencies or groups in Oregon that can help with your weed control questions. Be an active participant in preserving Oregon's natural resources by knowing the invasive plant fighters in your area.


Noxious Weed Control
635 Capitol St. NE
Salem, OR 97301
Phone: 503-986-4621
Fax: 503-986-4786