Skip to page content
  • Go to the main menu
  • Go to the search form
Metro

Main menu

▼
Open menu
▲
Close menu
  • Parks + Venues
    +
    Open this submenu
    −
    Close this submenu
    • Parks
      +
      Open this submenu
      −
      Close this submenu
      • Oxbow Regional Park
        +
        Open this submenu
        −
        Close this submenu
        • Camping at Oxbow
      • Blue Lake Regional Park
      • Smith and Bybee Wetlands Natural Area
      • Graham Oaks Nature Park
      • Cooper Mountain Nature Park
      • Mount Talbert Nature Park
      • Scouters Mountain Nature Park
      • Chehalem Ridge Nature Park
      • Canemah Bluff Nature Park
      • Newell Creek Canyon Nature Park
      • Orenco Woods Nature Park
      • Killin Wetlands Nature Park
      • Howell Territorial Park
      • Mason Hill Park
      • Broughton Beach
      • Glendoveer Golf Course and Nature Trail
      • Farmington Paddle Launch
      • Boat ramps
        +
        Open this submenu
        −
        Close this submenu
        • Chinook Landing Marine Park
        • M. James Gleason Memorial Boat Ramp
        • Sauvie Island Boat Ramp

      • Parks and nature activities
        +
        Open this submenu
        −
        Close this submenu
        • Guided nature activities
        • Nature learning resources
      • Picnics and special use
        +
        Open this submenu
        −
        Close this submenu
        • Picnics at Blue Lake
        • Picnics at Oxbow
        • Picnics at Graham Oaks
        • Picnics at Mount Talbert
        • Picnics at Scouters Mountain
        • Picnics at Chehalem Ridge
        • Picnics at Howell
        • Caterers and amusement providers
        • Special use permits
      • Water safety
      • Pets policy
      • Hunting policy
    • Venues
      +
      Open this submenu
      −
      Close this submenu
      • Oregon Convention Center
        +
        Open this submenu
        −
        Close this submenu
        • Oregon Convention Center hotel
          +
          Open this submenu
          −
          Close this submenu
          • Jobs and job training
          • Economic impact
          • Global reach
          • Hotel progress
      • Oregon Zoo
      • Portland Expo Center
        +
        Open this submenu
        −
        Close this submenu
        • Expo Future project
      • Portland'5 Centers for the Arts
    • Historic cemeteries
      +
      Open this submenu
      −
      Close this submenu
      • Services and fees
      • Visit the cemeteries
      • History of Metro's cemeteries

      • Brainard Cemetery
      • Columbia Pioneer Cemetery
      • Douglass Cemetery
      • Escobar Cemetery
      • Grand Army of the Republic Cemetery
      • Gresham Pioneer Cemetery
      • Jones Cemetery
      • Lone Fir Cemetery
        +
        Open this submenu
        −
        Close this submenu
        • Chestnut Grove Memorial Garden
      • Mountain View Corbett Cemetery
      • Mountain View Stark Cemetery
      • Multnomah Park Cemetery
      • Pleasant Home Cemetery
      • Powell Grove Cemetery
      • White Birch Cemetery
    • man and boy walking on trail at Oxbow Regional Park
      Buy a parks pass
  • Tools + Services
    +
    Open this submenu
    −
    Close this submenu
    • Tools for Living
      +
      Open this submenu
      −
      Close this submenu
      • Garbage and recycling
        +
        Open this submenu
        −
        Close this submenu
        • Find a recycler
        • Find your hauler
        • Metro Central transfer station
        • Metro South transfer station
          +
          Open this submenu
          −
          Close this submenu
          • Metro South trash cam
        • Code of conduct
        • Prep your load and pay less
        • Recycling at home
          +
          Open this submenu
          −
          Close this submenu
          • Home recycling collection
          • Glass
          • Metal
          • Plastic
          • Paper
          • Christmas tree recycling
        • Reducing waste at home
          +
          Open this submenu
          −
          Close this submenu
          • Waste-wise holidays
          • Stop junk mail
          • Back to school tips
        • Neighborhood collection events
          +
          Open this submenu
          −
          Close this submenu
          • 2023 neighborhood collection event schedule
        • Report dumped garbage
          +
          Open this submenu
          −
          Close this submenu
          • RID Patrol work transition program
          • Bag program
        • Ask an expert
      • Healthy home
        +
        Open this submenu
        −
        Close this submenu
        • Common hazardous products
          +
          Open this submenu
          −
          Close this submenu
          • Adhesives and glues
          • Aerosols
          • Air fresheners and deodorizers
          • Ammunition
          • Antifreeze
          • Arts and crafts supplies
          • Asbestos
          • Batteries, auto
          • Batteries, household
          • Bleach
          • Brake fluid
          • Carpet and rug cleaners
          • Chemistry sets
          • Cleaners, all-purpose
          • Degreasers
          • Detergents, dishwashing or laundry
          • Disinfectants
          • Drain cleaners
          • Fertilizers, chemical
          • Fingernail polish and remover
          • Flea control
          • Gasoline, kerosene and diesel fuel
          • Hair products
          • Hand cleaners, mechanic or painter
          • Lighter fluid, charcoal
          • Lubricating oils
          • Medicines, unwanted or expired drugs
          • Mercury- and PCB-containing items
          • Moss killer
          • Mothballs and moth crystals
          • Motor oil and oil filters
          • Oven cleaners
          • Paint and clear wood finish
          • Paint strippers or paint scrapings
          • Paint thinners
          • Paint, water-based
          • Pesticides
          • Photographic chemicals
          • Polishes and cleaners, metal
          • Polishes and waxes, wood furniture and floors
          • Polishes, cleaners or waxes, automotive
          • Polishes, shoe
          • Pool or spa chemicals
          • Septic tank cleaners
          • Sharps or medical waste
          • Smoke detectors, ionizing type
          • Soot remover or creosote destroyer
          • Stain and spot removers
          • Transmission fluid
          • Windshield wiper solution
          • Wood preservatives
        • Green cleaning
          +
          Open this submenu
          −
          Close this submenu
          • Air fresheners and deodorizers
          • All-purpose cleaners
          • Aluminum cleaners
          • Antiseptic soap spray
          • Bathroom soft scrub
          • Bronze, brass and copper cleaner
          • Chrome cleaner
          • Coffee maker cleaner
          • Countertop and appliance top cleaner
          • Dish soap
          • Disinfectants
          • Drain cleaner
          • Floor cleaners
          • Glass and window cleaners
          • Hand cleaner
          • Laundry bleach
          • Laundry cleaners
          • Leather cleaner
          • Oven cleaners
          • Scouring powder and paste
          • Silver cleaners
          • Spot and stain removers
          • Toilet bowl cleaners
          • Tub and tile cleaner
          • Urine stain removers
          • Wall cleaner
          • Wallpaper cleaner
          • Wet spotter
          • Windshield wiper fluid
          • Wood cleaners
          • Wood furniture polish
        • Home pest control
          +
          Open this submenu
          −
          Close this submenu
          • Ants
          • Asthma, pests and pesticides
          • Cockroaches
          • Fleas and ticks
          • Fruit flies
          • Mice and rats
          • Moths
          • Spiders
        • Buying safer cleaners
        • Storm and fire cleanup
        • Online learning
        • MetroPaint
          +
          Open this submenu
          −
          Close this submenu
          • Retail locations
          • Colors and product information
          • MetroPaint Swan Island Outlet
          • MetroPaint virtual painter
            +
            Open this submenu
            −
            Close this submenu
            • Living room
            • Bedroom
            • Dining room
            • Entrance
            • Upload a photo
      • Yard and garden
        +
        Open this submenu
        −
        Close this submenu
        • Learning gardens
        • Garden basics
          +
          Open this submenu
          −
          Close this submenu
          • Soil amendments
          • Mulch matters
          • Soil prep for your edible garden
          • Watering tips
        • Garden problems
          +
          Open this submenu
          −
          Close this submenu
          • Azalea lace bug
          • Aphids
          • Cabbage butterflies and leaf miners
          • Mosquitoes
          • Moles, voles and gophers
          • Slugs and snails
          • Yellowjackets
          • Wildlife issues
          • Lawn moss
          • Black spot, rust and rot
          • Powdery mildew
          • Weeds
          • Proper disposal of pesticides
        • Lawn
          +
          Open this submenu
          −
          Close this submenu
          • Mow
          • Grow
          • Water
          • Weed
          • Lawn alternatives
        • Plants
          +
          Open this submenu
          −
          Close this submenu
          • Native plants
          • Plant a shrub
          • Plant a tree
          • Fall and winter gardening
          • Growing roses
          • Getting started with edibles
        • Backyard habitat
          +
          Open this submenu
          −
          Close this submenu
          • Beneficial bugs
          • Pollinators
          • Protecting songbirds
          • Feeding and caring for wildlife
        • Composting
          +
          Open this submenu
          −
          Close this submenu
          • Composting methods
          • Tips for composting success
          • Compost trouble-shooting
          • Build a compost bin
          • Worm composting
          • Worm bin trouble-shooting
        • Grow Smart, Grow Safe
        • Garden pledge
    • Tools for working
      +
      Open this submenu
      −
      Close this submenu
      • Asbestos information for transfer station customers
      • Guide to construction salvage and recycling
      • Guide to managing paint waste
      • Guide to recycling and waste reduction at work
        +
        Open this submenu
        −
        Close this submenu
        • Guide to choosing single-use service ware
      • Business hazardous waste disposal program
        +
        Open this submenu
        −
        Close this submenu
        • Business hazardous waste disposal signup
      • Reducing food waste
        +
        Open this submenu
        −
        Close this submenu
        • Preventing food waste
        • Donating food
        • Composting food scraps
          +
          Open this submenu
          −
          Close this submenu
          • Composting options outside the Portland metropolitan area
        • Food scraps separation policy
      • Regional contractor's business license
        +
        Open this submenu
        −
        Close this submenu
        • Contractor's business license application and renewal
        • Contractor's business license lookup
      • Tools for haulers and facility operators
        +
        Open this submenu
        −
        Close this submenu
        • Accounts for haulers
        • Construction waste
        • Special waste disposal
        • Regional solid waste facilities
        • Solid waste tonnage dashboard
        • Forms for solid waste facilities
        • Rules, procedures and guidance
          +
          Open this submenu
          −
          Close this submenu
          • Recycling facility standards
        • Solid Waste Information System
        • Solid waste authorizations
          +
          Open this submenu
          −
          Close this submenu
          • Solid waste facility complaint form
          • License for Grimm’s Fuel Company
            +
            Open this submenu
            −
            Close this submenu
            • Updates
        • Public notices for garbage and recycling facilities
      • Travel options for employers
    • Tools for Partners
      +
      Open this submenu
      −
      Close this submenu
      • Grants and resources
        +
        Open this submenu
        −
        Close this submenu
        • Nature grants
          +
          Open this submenu
          −
          Close this submenu
          • Capital grants
            +
            Open this submenu
            −
            Close this submenu
            • Habitat restoration
            • Land acquisition
            • Neighborhood livability
            • Urban transformations
          • Nature education grants
          • Community stewardship and restoration grants
        • Large-scale community visions
        • Local share
        • Parks and Nature community partnerships
        • Community enhancement grants
          +
          Open this submenu
          −
          Close this submenu
          • Metro Central Enhancement Grants
        • Community Placemaking grants
          +
          Open this submenu
          −
          Close this submenu
          • How to apply
          • 2023 grantees
          • 2022 grantees
          • 2021 grantees
          • 2020 grantees
          • 2019 grantees
          • 2018 grantees
          • 2017 grantees
        • Civic engagement grants
        • 2040 planning and development grants
          +
          Open this submenu
          −
          Close this submenu
          • Past grant cycles
        • Regional Refresh Fund
          +
          Open this submenu
          −
          Close this submenu
          • Frequently asked questions
        • Regional Travel Options program
          +
          Open this submenu
          −
          Close this submenu
          • Safe Routes to School program
            +
            Open this submenu
            −
            Close this submenu
            • Safe Routes to School safety campaign toolkit
        • Investment and Innovation grants
          +
          Open this submenu
          −
          Close this submenu
          • 2021-22 Capital grants
          • 2021-22 Program grants
          • 2020-21 Program grants
          • 2019-20 Capital grants
          • 2019-20 Program grants
          • 2018-19 Grants
        • Brownfields assessment grants
          +
          Open this submenu
          −
          Close this submenu
          • Background
        • Transit-Oriented Development Program
        • Sponsorship opportunities
      • Guides and tools
        +
        Open this submenu
        −
        Close this submenu
        • Designing livable streets and trails
          +
          Open this submenu
          −
          Close this submenu
          • Conversations about performance-based design
        • Local transportation system plans
        • Jurisdictional transfer assessment
        • Mobility Corridors Atlas
        • Safe Routes to School Framework
        • Guide to equitable housing
          +
          Open this submenu
          −
          Close this submenu
          • Build Small Coalition
        • Planning parks with communities of color
        • Community Investment Toolkit
        • Regional Barometer
        • Greater Portland Economic Recovery Plan
        • Economic Value Atlas
        • Site readiness toolkit
      • Education resources
        +
        Open this submenu
        −
        Close this submenu
        • Resource conservation and recycling education
          +
          Open this submenu
          −
          Close this submenu
          • Elementary school classroom presentations
          • Middle and high school classroom presentations
          • Distance learning
            +
            Open this submenu
            −
            Close this submenu
            • Elementary online learning
            • Middle and high school online learning
            • Community and family online education
          • Publication library
          • Community workshops and events
          • Meet the educators
      • Data Resource Center
        +
        Open this submenu
        −
        Close this submenu
        • RLIS Live
        • Aerial photography
          +
          Open this submenu
          −
          Close this submenu
          • Regional Aerial Photo Consortium
        • Annexation and boundary changes
          +
          Open this submenu
          −
          Close this submenu
          • Annexation search tool
        • Unmanned Aircraft System program
    • Small thumbnail of a Metro map
      Regional Land Information System
  • What's Happening
    +
    Open this submenu
    −
    Close this submenu
    • Metro News
      +
      Open this submenu
      −
      Close this submenu
      • All Metro news
      • Land and transportation news
      • Parks and nature news
      • Home and garbage news
      • Venues news
      • Regional Snapshots
    • Public projects
      +
      Open this submenu
      −
      Close this submenu
      • Affordable housing bond program
        +
        Open this submenu
        −
        Close this submenu
        • Progress
        • Site acquisition
        • Background
        • Racial equity
        • Oversight
      • Supportive housing services
        +
        Open this submenu
        −
        Close this submenu
        • Progress
        • Racial equity
        • Regional coordination
        • Funding
        • Oversight
        • Stories
        • Common questions
      • Supportive housing services tax
        +
        Open this submenu
        −
        Close this submenu
        • Pay your tax
        • 2021 penalty waiver
        • Tax information
        • Codes and rules
      • 2023 Regional Transportation Plan
        +
        Open this submenu
        −
        Close this submenu
        • Building the plan
        • Engagement
        • Projects
        • Transit
        • Climate
        • Research
      • Greater Portland cleanup
        +
        Open this submenu
        −
        Close this submenu
        • Project highlights
      • 82nd Avenue transit project
        +
        Open this submenu
        −
        Close this submenu
        • Background
      • Tualatin Valley Highway transit project
        +
        Open this submenu
        −
        Close this submenu
        • Background
      • Tigard River Terrace urban growth boundary exchange
        +
        Open this submenu
        −
        Close this submenu
        • Background
      • Nature in Neighborhoods community choice grants
        +
        Open this submenu
        −
        Close this submenu
        • Share project ideas
        • How it works
      • Honoring untold stories at Lone Fir Cemetery
      • Parks and nature investments
        +
        Open this submenu
        −
        Close this submenu
        • About
        • History
        • Funding
        • Vision
        • Equity
        • Oversight
        • Leadership
      • Parks and nature bond measure
        +
        Open this submenu
        −
        Close this submenu
        • Bond progress
        • Background
        • Community engagement
        • Protect and restore land
      • Regional TSMO strategy
        +
        Open this submenu
        −
        Close this submenu
        • Equity
        • TSMO Resources
        • Meetings
      • Regional flexible funding for transportation
        +
        Open this submenu
        −
        Close this submenu
        • 2025-27 RFFA
        • Background
      • Regional mobility policy update
        +
        Open this submenu
        −
        Close this submenu
        • Background
      • Blue Lake Regional Park improvements
        +
        Open this submenu
        −
        Close this submenu
        • Background
        • Project updates
      • St. Johns Prairie bike and pedestrian trail
      • Garbage and recycling system facilities plan
        +
        Open this submenu
        −
        Close this submenu
        • Background
        • Engagement
        • Values and outcomes
      • Metro's commitment to Black lives
        +
        Open this submenu
        −
        Close this submenu
        • Policing
    • Calendar
      +
      Open this submenu
      −
      Close this submenu
      • calendar pictogram
        View meetings and events
    • Subscribe
      +
      Open this submenu
      −
      Close this submenu
      • newspaper pictogram
        Get news by email
  • About Metro
    +
    Open this submenu
    −
    Close this submenu
    • Regional leadership
      +
      Open this submenu
      −
      Close this submenu
      • What is Metro?
        +
        Open this submenu
        −
        Close this submenu
        • Cities and counties in the region
      • Metro Council
        +
        Open this submenu
        −
        Close this submenu
        • Council President Lynn Peterson
        • Councilor Ashton Simpson
        • Councilor Christine Lewis
        • Councilor Gerritt Rosenthal
        • Councilor Juan Carlos González
        • Councilor Mary Nolan
        • Councilor Duncan Hwang

        • How to give testimony
        • Find your councilor
      • Metro Auditor
        +
        Open this submenu
        −
        Close this submenu
        • About the Metro Auditor
          +
          Open this submenu
          −
          Close this submenu
          • Mission and authority
          • Process
          • Auditing standards
          • Audit Committee
        • Audits
          +
          Open this submenu
          −
          Close this submenu
          • Audit recommendations
        • Accountability Hotline
      • Metropolitan Exposition Recreation Commission
        +
        Open this submenu
        −
        Close this submenu
        • Commissioners
        • Materials archive
      • Metro advisory committees
        +
        Open this submenu
        −
        Close this submenu
        • Committee on Racial Equity
          +
          Open this submenu
          −
          Close this submenu
          • Committee on Racial Equity application
          • Meet the members
        • Joint Policy Advisory Committee on Transportation
          +
          Open this submenu
          −
          Close this submenu
          • Meeting materials archive
        • Metro Policy Advisory Committee
          +
          Open this submenu
          −
          Close this submenu
          • Meeting materials archive
        • Metro Technical Advisory Committee
        • Public Engagement Review Committee
        • Regional Waste Advisory Committee
        • Smith and Bybee Wetlands Advisory Committee
        • Transit-Oriented Development Steering Committee
        • Transportation Policy Alternatives Committee
          +
          Open this submenu
          −
          Close this submenu
          • TPAC materials archive
          • TransPort
      • Diversity, equity and inclusion
        +
        Open this submenu
        −
        Close this submenu
        • Know your rights
          +
          Open this submenu
          −
          Close this submenu
          • Complaint procedures
        • Accessibility at Metro
          +
          Open this submenu
          −
          Close this submenu
          • Request an accommodation
          • Accessibility plans
          • Website accessibility
          • File an ADA complaint
        • Language hub
          +
          Open this submenu
          −
          Close this submenu
          • Arabic
          • Cambodian
          • Chinese
          • Hmong
          • Japanese
          • Korean
          • Laotian
          • Nepali
          • Persian
          • Romanian
          • Russian
          • Somali
          • Spanish
          • Tagalog
          • Ukrainian
          • Vietnamese
        • Public engagement
        • Equity Dashboard
          +
          Open this submenu
          −
          Close this submenu
          • Workforce demographics
          • Job classifications
          • Employment status
          • Payscale
          • Recruitment
          • Retention
        • Construction Career Pathways
      • Public records
    • How Metro works
      +
      Open this submenu
      −
      Close this submenu
      • Organizational structure
      • Finances and funding
        +
        Open this submenu
        −
        Close this submenu
        • Financial reports
        • Metro budget
        • Property tax information
        • Income tax information
      • Metro Code
        +
        Open this submenu
        −
        Close this submenu
        • Metro administrative rules
      • Green Metro
        +
        Open this submenu
        −
        Close this submenu
        • Green Metro featured projects
      • Contract opportunities
        +
        Open this submenu
        −
        Close this submenu
        • Current requests for bids and proposals
        • Doing business with Metro
          +
          Open this submenu
          −
          Close this submenu
          • Payment information
          • Large construction contracts
        • Equity in contracting
      • Jobs
        +
        Open this submenu
        −
        Close this submenu
        • How to apply
        • Benefits
        • Pay
          +
          Open this submenu
          −
          Close this submenu
          • Classification descriptions
        • Labor unions
        • Diversity and equity
        • Training and development
        • Veterans' preference
        • First Opportunity program
        • Internships
          +
          Open this submenu
          −
          Close this submenu
          • Applying for internships
          • Types of internships
          • Garbage and recycling internships
        • Variable hour jobs
    • Library
      +
      Open this submenu
      −
      Close this submenu
      • Land use shelf
      • Transportation shelf
      • Nature shelf
      • Garbage and recycling shelf
      • Regional research shelf
      • Archives and special collections
    • photo of boats at Blue Lake
      Metro by the numbers

Search form

Metro News

Subscribe
photo of ludwigia at Smith and Bybee Wetlands

Our Big Backyard spring 2018

Explore great places and more in the spring 2018 issue of Our Big Backyard magazine.

 
  • العربية

'The game changer': Invasive ludwigia threatens to choke aquatic habitats, devastate ecosystems

photo of ludwigia at Smith and Bybee Wetlands Natural Area
Invasive ludwigia can double in size every two weeks, quickly overtaking waterways. Metro has been working since 2014 to control ludwigia at Smith and Bybee Wetlands Natural Area, where the plant can appear to stretch toward the horizon.

Invasive ludwigia can double in size every two weeks, quickly overtaking waterways. Metro has been working since 2014 to control ludwigia at Smith and Bybee Wetlands Natural Area, where the plant can appear to stretch toward the horizon.

photo of Willamette Riverkeeper volunteer and Rich Miller from Portland State University wading through ludwigia at Willamette Mission State Park near Salem
A Willamette Riverkeeper volunteer and Rich Miller from Portland State University wade through a dense mat of ludwigia while they collect aquatic invasive plant samples at Willamette Mission State Park near Salem.

A Willamette Riverkeeper volunteer and Rich Miller from Portland State University wade through a dense mat of ludwigia while they collect aquatic invasive plant samples at Willamette Mission State Park near Salem. Photo by Marci Krass

photo of Smith and Bybee Wetlands invasive ludwigia before treatment
BEFORE: Before and after photos from the same spot show the effect of a glyphosate-based herbicide treatment at Smith and Bybee Wetlands Natural Area

BEFORE: Before and after photos from the same spot show the effect of a glyphosate-based herbicide treatment at Smith and Bybee Wetlands Natural Area. Photo by Matt Mellenthin

photo of effects of ludwigia treatment at Smith and Bybee Wetlands
AFTER: Before and after photos from the same spot show the effect of a glyphosate-based herbicide treatment at Smith and Bybee Wetlands Natural Area

AFTER: Before and after photos from the same spot show the effect of a glyphosate-based herbicide treatment at Smith and Bybee Wetlands Natural Area. Photo by Matt Mellenthin

photo of kayaker paddling through ludiwigia-infested off-channel habitat downstream of Albany
Ludwigia has taken over many off-channel habitats downstream from Albany. The middle reach of the Willamette River has ideal conditions for ludwigia to thrive. Photo by Marci Krass

Ludwigia has taken over many off-channel habitats downstream from Albany. The middle reach of the Willamette River has ideal conditions for ludwigia to thrive. Photo by Marci Krass

  • ‹
  • ›
  • 1
  • 2
  • 3
  • 4
  • 5
Metro logo

'The game changer': Invasive ludwigia threatens to choke aquatic habitats, devastate ecosystems

By Yuxing Zheng
April 5, 2018 4:13 p.m.

Bylined articles are written by Metro staff and do not necessarily represent the opinions of Metro or the Metro Council. Learn more

At first glance, the delicate yellow flowers appear rather pretty. But glance up, and you realize the plant’s green leaves and branches stretch all the way to the horizon, blocking out most everything else. In just two weeks, this green monstrosity has doubled in size, growing into a thick, dense mat on the shoreline along Bybee Lake and into the water.

What is ludwigia?

Invasive ludwigia is an aquatic plant native to South America. Officials in Oregon started noticing a dramatic growth in ludwigia about five to seven years ago, likely after people dumped out aquariums with ludwigia in local waterways.

Ludwigia has several species and subspecies of ludwigia. Most of the ludwigia found along Willamette River backwaters is Ludwigia hexapetala, sometimes called water primrose or primrose willow. The kind found at Smith and Bybee Wetlands is Ludwigia peploides montevidensis. Ludwigia peploides is sometimes called floating primrose willow.

One kind of ludwigia is native to Oregon – Ludwigia palustris – but the plants are much smaller than the invasive varieties, and they do not compete with other native plants. The native ludwigia is sometimes called eastern false loosestrife or marsh seedbox.

This is invasive ludwigia, an aquatic plant native to South America that is threatening to choke backwaters, oxbow lakes and warmer river channels in Oregon. Ludwigia could destroy these special habitats and harm water quality, damaging native plants, amphibians, fish, birds and other wildlife. But it’s not too late to avoid the worst, and a network of groups is battling ludwigia, including Metro at Smith and Bybee Wetlands Natural Area in North Portland.

Ludwigia is the worst invasive aquatic plant in the state, said Glenn Miller, an invasive plants specialist at the Oregon Department of Agriculture.

“As I say to people in lectures, this one is the game changer,” he said. “It is so impactful that you’ll see open bodies of water that just convert to anaerobic mudholes in probably 20 years and really exclude most other life. No other aquatic plant we have had in the state does that.”

State officials first noticed a significant increase in invasive ludwigia about five to seven years ago when it started infesting Willamette River backwaters, such as Delta Ponds in Eugene. Since then, there have been infestations at Willamette Mission State Park near Salem, near Willamette Falls, Smith and Bybee Wetlands and other parts of the Willamette River system. Infestations have also been spotted in the Columbia Slough in Portland, Rogue River system in southern Oregon and in Central Oregon.

“The entirety of western Oregon and up through the Columbia River system and some parts of central and northeastern Oregon could be really susceptible to it,” Miller said.

Experts suspect ludwigia arrived in Oregon through the aquarium and aquatic garden trades. The plant is popular in aquariums, which often get dumped into local waterways when people no longer want them.

photo of ludwigia infesting Black Dog Landing near Albany
Ludwigia has completely infested a side channel at Black Dog Landing near Albany. Photo by Travis Williams

Devastating impacts

Ludwigia has the potential to devastate aquatic ecosystems.

“You’d most likely see a decline in the native populations of turtles, amphibians and fish in the Willamette and Rogue systems,” Miller said. “These are unique habitats that were formed when the river meandered, and we’re losing them.”

Help tackle ludwigia

Interested in joining the fight against invasive ludwigia?

Please clean, drain, and dry boats and gear after all outings on water.

If you spot invasive ludwigia, report it to the Oregon Invasive Species Hotline.

Join the Willamette Aquatic Invasives Network and contribute to a community map of ludwigia.

Native plants form the basis of healthy habitats that provide food and shelter for native animals. For instance, Smith and Bybee Wetlands is an important stopover for migratory birds to rest and refuel as they fly to and from the Arctic. But when invasive ludwigia covers an area, migrating shorebirds can’t stick their beaks in mudflats to eat bugs, and wintering ducks and waterfowl find less rice cutgrass and other native seeds and plants.

Ludwigia can also lead to poor water quality, said Elaine Stewart, a senior natural resources scientist at Metro. The dense mat of ludwigia on the water surface and decomposition as it dies deplete oxygen from the water. Low oxygen is bad because native fish and invertebrates that live in the wetlands need oxygen. It could also make water quality bad for salmon.

“Ludwigia can throw an entire ecosystem out of balance,” Stewart said. “Complexity is good in an ecosystem, and ludwigia simplifies it.”

A network of people is trying to prevent that from happening in the Willamette River system. Formed in 2014, the Willamette Aquatic Invasives Network meets quarterly, and members represent more than 60 government agencies, land trusts, nonprofits, universities, businesses and community members.

The network is forming a steering committee to develop a comprehensive aquatic invasive species action plan, said Marci Krass, the network coordinator and restoration program manager at the nonprofit Willamette Riverkeeper.

“There’s a lot of enthusiasm in helping to save these backwater habitats,” said Matt Mellenthin, a network member and a habitat restoration coordinator at Integrated Resource Management, a company based in Philomath. “Just about everybody in the environmental field clearly sees how important the habitats being taken over by ludwigia are. Whether it’s for salmon rearing or water quality, there are just a lot of partners working on this stuff together.”

Metro has hired Mellenthin’s company to help control ludwigia at Smith and Bybee Wetlands – and it’s not the only one.

“The first year we worked at Delta Ponds (in Eugene), it was the first large-scale ludwigia treatment in Oregon,” Mellenthin said. “In a five-year span, we’ve gone from one project to 13 large projects throughout the Willamette Valley, from Eugene to Smith and Bybee.”

Invasive ludwigia can also significantly reduce recreational opportunities. Infested areas often cannot be accessed by motorized or nonmotorized boats.

  • photo of small fragment of ludwigia
    Small fragments of ludwigia can easily spread and grow, causing new infestations downriver.

  • photo of Ludwigia peploides montevidensis leaves
    Ludwigia peploides montevidensis leaves can appear more pointed when growing on land.

  • photo of Ludwigia hexapetala
    Ludwigia hexapetala leaves can appear more rounded when growing on water.

Protecting Smith and Bybee Wetlands

Seemingly hidden among industrial warehouses in North Portland, Smith and Bybee is one of the largest urban wetlands in the country. At nearly 2,000 acres, the natural area is home to beavers, river otters, black-tailed deer, western painted turtles, blue herons, osprey, bald eagles and many other animals. It’s also a popular paddling destination in the winter, and people walk the trails year-round.

Metro staff first spotted invasive ludwigia at Smith and Bybee Wetlands in the mid-2000s, said Justin Cooley, a natural resources technician at Metro who has coordinated the efforts to control ludwigia. Metro and Portland State University experimented with control efforts beginning in 2010.

Large-scale treatments started in 2014, thanks to money from the parks and natural areas levy approved by voters the previous year. In 2014 and 2015, intense treatments from July through September helped keep ludwigia under control. In 2016, crews faced their biggest challenge, tackling a 60-acre monoculture that had developed on Bybee Lake. The goal is to contain ludwigia and prevent it from spreading further, but it’s unlikely that it will be eradicated.

“We are doing everything we can to try to get this down,” Cooley said. “Right now we’re at a point where we can manage it.”

The fight isn’t easy. Ludwigia is hardy and stubborn. It typically starts growing along the shorelines and quickly makes its way into lakes and rivers.

“It’s an early colonizer as the mud flats are exposed,” Cooley said. “It can outcompete any of the native plants, such as the forbs, sedges and rushes.”

Ludwigia will spread on the surface of the water, and parts of the plant will drop down. Eventually the roots are attached to the bottom of the lake or river. Special roots even feed oxygen to the plant in low-oxygen environments.

Each year, contractors start by hand pulling and spraying a glyphosate-based herbicide on ludwigia growing around the lake. The first round of treatments usually occurs in late June using canoes to reach floating mats away from the water’s edge. The herbicide prevents floating mats of ludwigia from taking root on the lake bed as the water level drops, ensuring migrating birds will have access to open water and mudflats to feed on native plants.

As new plants grow on the exposed lake bed, crews strap on 4½ gallon backpack sprayers and walk around to treat the ludwigia. At the height of the growth, crews use a 700-foot hose connected to an ATV to reach patches far from solid ground.

“It is tiring work,” Cooley said. “The crew is wearing chest waders and slogging through mud.”

Herbicides are the most effective method of treating ludwigia, especially on a large site, but they’re used with caution. The weed killer used to treat ludwigia is approved by the Environmental Protection Agency for use in and near water.

Hand pulling ludwigia is not feasible as the only tactic at a large site like Smith and Bybee Wetlands. It must be done with care, since hand pulling can spread ludwigia, which easily grows new colonies from small fragments that break free and float away. It also spreads by seeds.

Come June, another round of treatments at Smith and Bybee Wetlands will start in the ongoing effort to control ludwigia.

“I’m hopeful we’ve turned the corner and are pushing ludwigia down,” said Stewart, the Metro scientist. “Invasive species are forever. It takes a lot of resources.”

Previous: Part 1

Learn more about the invasive plant that experts say is a "game changer" that could turn open bodies of water into mudholes within 20 years. Read about invasive ludwigia in the spring issue of Our Big Backyard, Metro's quarterly parks and nature magazine. Plus, find out about fun nature outings, classes and other news.

Next: Part 3

Any home gardener knows that pesky invasive plants can appear anytime. Here are seven invasive plants that gardeners can tackle in the spring, before they bloom and scatter seeds.
 

Footer Menu

▼
Open menu
▲
Close menu
  • Services of Metro
    +
    Open this submenu
    −
    Close this submenu
    • Oregon Zoo
    • Oregon Convention Center
    • Portland Expo Center
    • Portland'5 Centers for the Arts
    • Data Resource Center
    • Garbage and recycling facilities
    • Metro cemeteries
  • Opportunities
    +
    Open this submenu
    −
    Close this submenu
    • Jobs
    • Contracts
    • Grants
    • Franchising and licensing
  • Access
    +
    Open this submenu
    −
    Close this submenu
    • Know your rights
    • Accessibility at Metro
    • Language assistance
    • Feedback and questions
    • Metro Accountability Hotline
    • Privacy policy
    • Request public records
    • Directions
  • Leadership
    +
    Open this submenu
    −
    Close this submenu
    • Metro Council
    • Metro Auditor
    • MERC
    • Committees
    • Who's my councilor?

Metro logo

Whether your roots in the region run generations deep or you moved to Oregon last week, you have your own reasons for loving this place – and Metro wants to keep it that way. Help shape the future of the greater Portland region and discover tools, services and places that make life better today.

Contact Metro

  • 503-797-1700
  • 503-797-1804 TDD
  • Send a message

Connect with Metro

Subscribe to Metro News

More subscription options

Find Metro on

Facebook Twitter YouTube LinkedIn Instagram