lesser celandine
lesser celandine

Invasive Plants

Weeds are plants growing in places where they are not wanted. Invasive weeds are non-native plants that can cause harm to the natural environment, humans and animals. The Oregon Department of Agriculture estimates that Oregon spends $81 million annually on the control of invasives species. Weed management is an on-going activity. Weeds that appear to be suppressed may re-emerge. Reducing soil disturbance along with regular monitoring and weed removal are the keys to weed control. 

Pathways and Prevention Weeds are often introduced by human activities. Some weeds (like Himalayan blackberry) are brought in for agricultural purposes, others (like reed canarygrass) may be imported for erosion control, and many (like butterfly bush) have been introduced through the nursery trade. Once present, weeds can be spread by people, birds, wildlife, wind, water, machinery and other means. 

Follow these practices to help limit the spread of invasive weeds on your property and throughout the county: 

  • Play, clean, go.

    After working with or walking through weeds, remove any plant parts from your apparel and gear before moving to another area.

  • Grow native.

    Use only native or non-invasive species when planting new vegetation.

  • Right plant for the right place.

    Carefully choose pond plants to avoid accidentally introducing weedy aquatic species.

  • Don’t let it loose.

    Never dump aquarium contents down any drain. Seal in a bag and put in the trash.

  • Buy it where you burn it.

    Buy fire wood locally. Weeds and pests can be transported in wood.

  • Clean, drain, and dry.

    Clean boats of all vegetation and aquatic life after each use.

Contractors pulling invasive water primrose © M. Mellinthin
Contractors pulling invasive water primrose © M. Mellinthin


Look for new invaders every time you are outdoors. Scan the area and pay special attention to: 

  • Pathways

    Roads, trails, edges

  • Habitats

    Aquatic plants in water bodies, understory plants on forest floor, etc.

  • Distribution

    Plants that seem out of place

  • When you find something:

    • Double check the ID (consult a guidebook or contact an expert at Benton SWCD or OSU Extension Master Gardeners). 
    • Record the location on a map. 
    • Record the size of the infestation (# of plants, area covered). 
    • Take a digital photo of the plant. 
    • Go to oregoninvasiveshotline.org to report with as much info as you have.

    Make a Report

Weed Management Strategies

Property owners will benefit greatly from working with neighbors on weed management because of the transient nature of weeds. Be aware that certain weeds require different management strategies to control. Identifying weed threats on your property is the first step to early detection and rapid response. Prevention is the most cost effective line of defense. Keep your property covered with desirable vegetation and make sure not to transport weeds. Use native or non-invasive vegetation to out-compete noxious weeds. 

Quickly respond to any new weed infestation.Common weed control techniques include:

  • Physical

    Hand-pulling weeds before they set seed can help stop them from spreading.

  • Mechanical

    Mow, rake or use powered tools and machinery to manage weeds. 

  • Grazing

    Allow livestock to graze weeds before they go to seed. Since animals can transport seeds, don’t move them from a weedy area to a weed free area. 

  • Chemicals

    Herbicides are commonly used to kill weeds. Be sure to read the product label prior to application. Use the weather (e.g., wind direction), buffers or other practices to minimize any transport of chemicals away from the target plant by runoff or drift.

lesser celandine
lesser celandine

Invasive Plant Database

View images and plant information to become familiar with the plants you see in your yard and around the county.

Attend a Weed Pull

Attend a weed pull and learn how to identify native plants and noxious weeds. Join a Love Your River workshop or paddle and weed pull day on the Willamette River, hosted by members of the Willamette Mainstem Cooperative. Or join us at the Let’s Pull Together Event during Oregon’s Invasive Weed Awareness week each spring at one of our local parks to pull weeds from the places we love with members of the Benton County Cooperative Weed Management Area.

2014 CWMA Group
2014 CWMA Group

Benton County CWMA

Learn more about the cooperative weed management area.

Related Blog Posts

Michael Ahr and Tamra Dickinson going after Ludwigia and Yellow floating heart on the Willamette this past summer.
Notes from the Field: Willamette Mainstem Cooperative in 2021
Troy Abercrombie | October 29, 2021

In April of 2021, Benton SWCD welcomed Michael Ahr as our Natural Resources Conservation Program Manager. Michael immediately hit the ground running as he and his team took on multiple inventories on the Willamette this summer, searching out Ludwigia and yellow floating heart and complementing the work of colleagues from Willamette Riverkeeper.

The Impacts of Nonnative Plants on Birds
Lauren Pharr | April 28, 2021

In my blog post The Native Link: The Importance of Native Plants to Birds, I describe the importance of native plants to the ecosystem, and more specifically, how birds benefit from native plants. But what exactly is the problem with nonnative, and more specifically invasive, plants and how do they affect birds and the ecosystem

front cover of the 2020 guide to aquatic plants
Water Weed Guide
Heath Keirstead | July 13, 2020

The 2020 edition of the water weed guide includes 18 aquatic weeds of concern for Benton County and their native and non-native look-alikes.

Explore More

#invasive species

Related Resources

For additional information, we recommend:
  • Landowners Invsp

    A landowner’s guide to invasive species for Benton County, Oregon. This brochure includes meadow knapweed. old man’s beard, knotweed, impatiens, yellow archangel, and false brome.

  • Hunters Invsp

    Weeds are one of the greatest threats to elk, destroying more than 3 million acres of elk habitat a year. You can prevent the loss of foraging habitat by learning to identify invaders and reporting them. Your actions can save foraging habitat, so that the hunters of today and tomorrow have elk to hunt.

  • BackyardInvSpp

    Pretty invaders found in your backyard and some removal recommendations.

  • FarmersInvSpp

    Farmer’s guide to invasive species – invasive weeds in your back forty. Six key invasive weeds to have in your farm’s early detection, rapid response plan.

  • Bentoncoweeds

    A selection of Benton County invasive weeds including butterfly bush, teasel, Canada thistle, tansy ragwort, English ivy, garlic mustard, meadow knapweed, Japanese knotweed, Scotch broom, spurge laurel, and false brome.

Program Contacts

Michael Ahr
Michael Ahr
Natural Resources Conservation Program Manager
541-231-2615 (work cell) 541-753-7208 ext. 202 (office direct line)
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