Luckiamute Watershed Council
Spread the word!
  • Home
    • LWC Newsletter
    • Resources >
      • Purchase "Writing Our Watershed" Book
      • LWC Info & Resources
      • Outdoor Recreation
      • Community Science
      • Willamette Report Card
      • FAQs
      • Watershed Health >
        • DEQ Well Testing
        • DEQ Pruebas de Pozos
      • Web Resources
    • Members Only (Log-In Required)
  • About
    • COVID-19
    • Our Council
    • Our Team >
      • Become a Member
    • Our Watershed
    • Our Partners
    • Strategic Plan 2019
    • LWC Annual Reports
    • Monthly Meeting Details
    • Board Meeting Minutes
  • Projects
    • Annual Projects Summary
    • Ash Creek Restoration Project
    • Luckiamute State Natural Area Enhancement >
      • Visiting LSNA
      • LSNA Reconnection >
        • LSNA Reconnection Documents
    • Knotweed Control >
      • Knotweed Resources
    • Upper Luckiamute Focus Area >
      • NetMap
      • South Fork Pedee Enhancement
      • Upper Price Creek Restoration Project
      • Maxfield LW Placement
      • Upper Ritner Project
      • Maxfield Creek Restoration
    • Water Quality Monitoring
    • Upper Luckiamute Side Channel Reconnection Project
  • Get Involved
    • Donate
    • Sign up for Emails!
    • Friends of the LWC
    • Business Circle >
      • Join the Business Circle!
    • Volunteer >
      • Volunteer Safety Guidelines
      • Adopt A Road
      • Volunteer Pledge
    • Volunteer Interest Form
    • Join our EnO Committee!
    • Join our Fundraising Committee!
    • Become a Member
  • Events
    • One Million Plants!
    • Sips and Science: 20 Years of Restoration
    • Native Plant Workshop
    • 2021 SWCD Native Plant Sales
    • Love Your Watershed (at Home)! >
      • Stay at Home Activities >
        • Community Science
        • Identify Your Watershed
        • Plant ID Apps
        • Educational Films
      • Find A Fish!
    • Event Archives >
      • Sips and Science: LSNA Birds
      • Sips and Science: Plant Nurseries
    • Calendar
  • Donate
    • Join the Business Circle!
    • Donate to the Love Your Watershed Program! >
      • 2020 LYW Fundraiser Results
    • Donor Spotlight 2020
    • Donor Tiers
    • LWC Wish List
  • LWC Store
    • Face Masks
    • Watershed Book

Knotweed Identification and Control

Knotweed is fast growing and extremely aggressive. It invades river and creek banks, permanently displaces native vegetation, destroys critical fish and wildlife habitat, and reduces recreational opportunities.

After only a few years, it can be virtually impossible to control knotweed if left unchecked, so please ACT NOW by educating yourself.

  • What does knotweed look like?
  • How does knotweed spread?
  • How can knotweed be controlled?
  • What can I do about knotweed?

Download the pdf here to learn how to help save Pacific Northwest rivers from knotweed!
Picture

Seasonal Guide to Identifying Japanese Knotweed

Picture
Knotweed is a bamboo-like perennial that grows in dense stands 6 to 12 feet tall. It has hollow, reddish cane-like stems with swollen stem nodes that are surrounded by thin papery sheaths. Leathery, spade-shaped leaves are arranged in an alternating pattern along the stems. The former popularity of Japanese knotweed as an ornamental shrub stems from their attractive flower clusters, which emerge during late summer and fall. These showy, plume-like clusters contain hundreds of small, creamy white to greenish white flowers and extend upward from the upper leaf axils. The fruits are 3-sided and papery, each containing one glossy dark seed.

Picture
At the end of the growing season, the plants die back to the ground. However, the dead reddish brown canes often persist throughout the winter. These dry canes can be a fire hazard and can also impede access to streams by both people and wildlife. Additionally, due to knotweed's ability to sequester nutrients into its root system at the onset of winter, dead knotweed canes and leaf litter have less value than our native deciduous plants as a food source for soil microbes and aquatic invertebrates, which could have a negative impact on the aquatic food web.

Picture
 In early summer, the stems emerge from rhizomes deep underground to shoot to over 2.1m (7ft), suppressing all other plant growth in the area. These canes grow quickly and are incredibly strong - even puncturing asphalt, concrete and brick in an effort to reach sunlight. Underneath the ground, the root system is extensive and can persist over many years. If you attempt to dig out the roots of a knotweed patch, you should NEVER put any of the root or stem material in your compost or yard waste. You must carefully gather all root and stem material, bag it, and throw it in the garbage.

Picture
In late summer and fall, the knotweed plant prepares for the winter by sending sugars and nutrients to the plants’ rhizomes. As a result, herbicide applications are most effective after flowering, and up until the first killing frost. However, if you are planning to tackle knotweed with herbicides, it’s a good idea to wait until after the plants are done flowering to limit impacts to pollinators. About a month after it has been successfully treated, you will notice knotweed leaves beginning to curl and turn brown (see photo to the left). Review the videos posted below to determine the best treatment strategy for your property.

Instructional Videos - How to Indentify and Treat Invasive Knotweed

A BIG thank you goes to King County, for giving us permission to use and modify these excellent instructional videos! Although these videos were made in Washington state, the information is relevant to the Luckiamute watershed.
Introduction to Knotweed
About the plant, how to identify it, and how it damages river banks.
How to control knotweed without chemicals (for small infestations)
If you have a small knotweed patch, watch the following video to learn about digging out this invasive weed, cutting and starving roots, and cutting, covering and shading roots as control methods. NOTE: This labor-intensive method is suitable for small patches of knotweed only.
How to control knotweed using herbicide spray
Learn how to apply chemical herbicide on knotweed using a backpack sprayer.
Picture


Luckiamute Watershed Council • Your Land. Your Rivers. Your Community. Your Watershed.