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Tansy Ragwort

Senecio jacobaea
Updated Nov 04, 2022
 
1

Make a Positive Identification

  • Tansy ragwort is an herbaceous plant (soft stems and leaves) with yellow flowers. The stems grow upright 0.5–4 feet tall. It is a widespread weed in the Pacific Northwest.
  • Its life cycle is biennial. Following germination, tansy ragwort forms a rosette with shallow roots. The rosettes have light-green leaves that grow close to the ground. During its second growth year, one or more flowering stems form.
  • Mature plants produce 100,000 seeds or more. Tansy ragwort spreads easily by seed.
  • It forms dense stands and crowds out other herbaceous plants.
Species: Tansy Ragwort
Flowering tansy ragwort plants in field

Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Tansy ragwort stems grow 1.5–4 feet tall. It forms dense stands. Tansy ragwort thrives in areas with disturbed soil.

Species: Tansy Ragwort
Examples of tansy ragwort leaves

Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Its leaves are dark green on top and lighter underneath. They have deeply lobed leaves with a ruffled look.

Species: Tansy Ragwort
Tansy ragwort flowers

Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Tansy ragwort has yellow, sunflower-family flowers. They have 15-ray flowers that look like petals.

Species: Tansy Ragwort
Tansy ragwort rosette

Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

After a tansy ragwort seed germinates, plants form a rosette. The rosettes have light-green leaves that grow close to the ground. The leaves are lobed.

Species: Cinnabar Moth
Cinnabar moth larvae on tansy ragwort flowers

Whiteway, iStock

The cinnabar moth (Tyria jacobaeae) was introduced to the Pacific Northwest as a biological control for tansy ragwort. The larvae have distinct orange and black stripes, which can help you to identify tansy ragwort. The larvae of the moth defoliate tansy ragwort. See below for information about biocontrol.

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LOOK-ALIKES: COMMON TANSY AND ST. JOHNSWORT
Species: Common Tansy
Common tansy flowers with foraging bumble bees
Common tansy leaves
Photo credits
Right:

Alexis, CC BY 4.0, via Wikimedia Commons

Common tansy (Tanecetum vulgare) also has lobed green leaves and yellow flowers. But its flowers are button-shaped. They don’t have the ray flowers. Common tansy is also weedy, but not as aggressive as tansy ragwort. It is less poisonous to livestock. Control methods for common tansy are similar to the solutions for tansy ragwort.

Species: Common St. Johnswort
Common St. Johnswort flower head

Steve Dewey, Utah State University, Bugwood.org

Common St. Johnswort (Hypericum perforatum) is another weedy plant species with yellow flowers. It has star-shaped flowers with five petals as shown in the photo. Its stems are reddish compared to tansy ragwort. It grows upright to 1–2.5 feet tall.

 
2

Tansy Ragwort Benefits

  • Tansy ragwort is an invasive weed. It doesn’t have any benefits for people or the environment.
 

Tansy Ragwort Risks

  • If left unmanaged, tansy ragwort forms dense stands. It crowds out other herbaceous plants.
  • It has little food value to native animals and insects.
  • Tansy ragwort reduces the habitat value of an area by excluding native plants.
  • Tansy ragwort is toxic to all livestock, especially cattle and horses.
Risk Card
Does it cause harm?
Adults & Children
Some
Property
High
Pets
Very High
Annoyance
High
Environment
High
Action Highly Recommended
 
3

Take Action

If you have tansy ragwort on property you manage, control it to limit the spread.

Do I need to take action?
Yes. Remove individual plants and small patches. Established patches require several years to control.

What if I do nothing?
Tansy ragwort will spread by seed and take over areas.

If you believe your horses or cattle have eaten tansy ragwort, contact your veterinarian right away. Both fresh and dried tansy ragwort plants are toxic to horses and cattle. Sheep and goats are less susceptible to tansy ragwort poisoning.

NEED HELP?

Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon  and other states  can suggest other methods.

 
4
Solutions for Tansy Ragwort

Early Detection & Rapid Response

Watch for tansy ragwort on property you manage. Remove it before it becomes a bigger problem.

Physically Remove Plants & Non-Chemical Options

  • Dig out plants by the roots when the soil is moist. Place tansy ragwort stems, roots, and flowers into thick plastic bags. Dispose of these materials in the trash. Or take the bags to the sanitary landfill.
  • Seedlings germinate in the late summer, fall, and spring. Seedlings are easier to kill than larger plants.

Herbicides (Weed Killers)

Herbicides effectively control tansy ragwort when used according to the label instructions.

Monitoring & Follow-Up

Following removal, return to the area every 2–3 months. Look for regrowth and seedlings. Take action as needed.

Jump To

Method Does it work? Is it safe? Recommendation
A
Physically Remove Plants
Effective
Low risk
Recommended
B
Biocontrol for Tansy Ragwort
Somewhat effective
Low risk
Recommended
C
Herbicides Triclopyr & Glyphosate
Effective
Moderate risk
Use if Necessary
D
If Using Herbicides, Protect Yourself & Minimize Risks
E
Prevent Tansy Ragwort
 
A

Physically Remove Plants

Non-Chemical Method

Weston Miller, Oregon State University

Physically Remove Plants

Recommended
  • Hand-pull tansy ragwort by grasping the center of the plant close to the ground. Or dig out plants with tools.
  • Remove as much of the root system as possible.
Does it work?
Effective

Use preventive measures for best results.
How much effort?
High effort

Plants have deep roots and are challenging to remove.
What's the risk?
Low risk
Possible risk of exposure or harm from chemicals
NONE

Tansy ragwort is easiest to remove when the soil is moist. Pull or dig out plants by the roots to keep them from regrowing.

Bags of invasive plants on a trailer ready for the sanitary landfill

Chris Evans, University of Illinois, Bugwood.org

Put tansy ragwort plants in a sturdy plastic bag. Place the bag in the trash or take it to a sanitary landfill. The photo shows bags of invasive plants on a trailer ready for the sanitary landfill.

 
B

Biocontrol for Tansy Ragwort

Non-Chemical Method

Whiteway, iStock

Biocontrol for Tansy Ragwort

Recommended
  • Noxious weed management agencies in the Pacific Northwest recommend 3 insects that feed on tansy ragwort.
  • Check that you have the biological agents present at your site.
Does it work?
Somewhat effective
  • Biocontrol on its own won’t get rid of tansy ragwort. Combine it with other control methods.
  • Use preventive measures for best results.
How much effort?
Low effort
  • Collect insects from an established stand of tansy ragwort.
  • Distribute the insects on broom plants at your site.
  • Monitor your site for biocontrol insect activity.
What's the risk?
Low risk
Possible risk of exposure or harm from chemicals
NONE
Cinnabar moth larvae on tansy ragwort plant

Cinnabar Moth

  • Cinnabar moth (Tyria jacobaeae) larvae feed on tansy ragwort leaves and flowers. The larvae strip plants of their leaves and flowers. Flowers may regrow in the late summer.
  • Cinnabar moth larvae also feed on related plants, including native and horticultural plant species.
Tansy ragwort flea beetle larvae feeding on tansy ragwort roots

Mark Schwarzlander, University of Idaho, Bugwood.org

Tansy Ragwort Flea Beetle

  • Tansy ragwort flea beetle (Longitarsus jacobaeae) larvae and adults feed on tansy ragwort. Adults feed on the leaves and make tiny holes. Larvae feed within the roots.
  • Sites where flea beetles were released show over 90% control of tansy ragwort after seven years.
Ragwort seedhead fly larva feeding on tansy seedhead

Eric Coombs, Oregon Department of Agriculture, Bugwood.org

Ragwort Seedhead Fly

  • Ragwort seedhead fly larvae (Botanophila seneciella) feed within seed heads.
  • They destroy developing seeds.

Biocontrol Tips

  • Both the tansy flea beetle and the cinnabar moth are well established in western Oregon. Numbers go up and down with the ebb and flow of tansy ragwort populations.
  • Consider including biocontrol agents in your long-term tansy ragwort control plan by leaving plants that have the cinnabar moth caterpillars on them or watching for the tell-tale holes in the leaves of tansy rosettes in October.
  • A strong pasture with little bare ground will resist weeds like tansy ragwort.
  • Call your local Extension office or Soil and Water Conservation District for help in grazing management to reduce the risk of tansy ragwort and other weeds.

How to Collect Biocontrol Insects

  • Collect insects from established stands of tansy ragwort. Use a stick to strike plant stems and collect the insects on a fabric or paper surface.
  • Transport the collected insects to your tansy ragwort infested area in a container. Provide cool, dry, and uncrowded conditions in ventilated containers. Include fresh tansy ragwort stems, leaves, and flowers in the container. Release the insects as soon as possible.
  • Distribute the insects onto tansy ragwort plants. 

Biocontrol Reference

For more information about biocontrol for tansy ragwort, see Weed Biological Control  (Oregon Department of Agriculture).

 
C

Herbicides Triclopyr & Glyphosate

Chemical Method: Use with caution

Chameleonseye, iStock

Herbicides Triclopyr & Glyphosate

Use if Necessary

Herbicides that contain the active ingredients triclopyr and glyphosate effectively control tansy ragwort when used according to label directions.

Does it work?
Effective
  • Several years of monitoring and effort may be necessary to get rid of tansy ragwort.
  • Use preventive measures for best results.
How much effort?
Moderate effort
  • Treat individual tansy ragwort plants and patches.
  • Return to the area each year and take action as needed.
What's the risk?
Moderate risk
  • Herbicides come with real risks. ALWAYS read the entire label front to back. Review instructions even for brands you know.
  • Herbicides can run off your site into waterways and may harm wildlife. See How to Keep Pesticides Out of Waterways.
Possible risk of exposure or harm from chemicals
Using herbicides includes some amount of risk. The lowest risk comes with using alternative methods.

You may be exposed to an herbicide if you:

  • Get it on your skin
  • Breathe it in
  • Eat or smoke afterward without washing hands
  • Touch or eat plants that are wet with spray (you, pets, or children)
  • Bring it inside on your shoes or clothes

Follow directions closely to reduce risk.

Herbicides with active ingredients triclopyr and/or glyphosate, used individually or in a mixture, are effective chemical treatments for tansy ragwort. Look for these chemical names in the “Active Ingredients” section of product labels.

Photo of herbicide label highlighting active ingredient triclopyr

Weston Miller, Oregon State University

  • The white box on this example product label highlights active ingredient triclopyr. Text on the label states “Kills completely.”
  • Triclopyr doesn’t injure most grasses. It’s a good choice for treating tansy ragwort that is growing next to desired grasses in lawn, pasture, and meadow areas.
Photo of herbicide label highlighting active ingredient glyphosate

Weston Miller, Oregon State University

  • The white box on the example label highlights active ingredient glyphosate. The text on the label states “Kills grass and weeds around flower beds, trees, shrubs....”
  • Glyphosate will damage most plants and grasses. Don’t let the spray contact plants you want to keep.

Herbicide Application Tips

  • Apply herbicide to actively growing tansy ragwort seedlings and rosettes. Follow the label directions.
  • Seedlings germinate in fall and spring. Less herbicide is required to spray seedlings than established plants.
  • Don’t treat tansy ragwort plants that have already flowered. Herbicide applications are not effective after flower stalks start forming. Dig out and bag plants that have already flowered.
  • Expect that some tansy ragwort will regrow after treatment with herbicides. New seeds will germinate. Look for regrowth and seedlings. Control as needed.
Minimize the potential impact of herbicides to bees and other pollinators. Treat tansy ragwort plants before they flower. Or apply herbicides in the morning or evening when bees are less active. Avoid spraying pollinators directly. For more information, see OSU’s How to Reduce Bee Poisoning from Pesticides  
 

If Using Herbicides, Protect Yourself & Minimize Risks

Chemical Method: Use with Caution
Great blue heron in marsh

Why is it important to read herbicide labels?

  • They have detailed information on how to use the product correctly and legally.
  • They contain information on potential hazards of the product.
  • They provide instructions you should follow for poisonings and spills.
  • Following label instructions helps you to minimize the risks and maximize the benefits.

Key Herbicide Safety Tips

  • Read the entire label front to back.
  • Follow the instructions.
  • Review the instructions even for brands you know.
  • Only apply the product where the label says it may be applied.
  • Be precise in your application. More is not better.

The Label is the Law

ALWAYS read the label before using herbicide products. The label is a legal document that provides information on how to safely use the herbicide. This helps avoid harm to human health and the environment. Using an herbicide in off-label ways is illegal. It can result in legal enforcement actions.

READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.

  • Labels are different for every product and they often change over time.
  • Use a magnifying glass if needed.
  • Pay attention to CAUTION, WARNING, and DANGER statements.
  • Pay attention to the PRECAUTIONARY STATEMENTS.
  • The law states you must read and follow herbicide instructions.

Protect Yourself
Eye, skin & lung irritants

  • Wear the right protective gear. This often includes chemical-resistant gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
  • Mix outdoors or in a well-ventilated area.
  • Wash hands after mixing or applying, and before eating or smoking.
  • Take a shower immediately after handling herbicides.
  • Wash clothes worn while mixing or applying separately from other laundry.

Protect Children & Pets
Children and pets are at risk if they eat or touch the plants before it dries.

  • Keep them away during and after applying herbicides (read label for how long).
  • Remove toys and pet dishes from yard before applying.
  • Don’t track herbicide products into your home on shoes or clothes.

Protect Plants You Want to Keep

  • Glyphosate and similar herbicide ingredients damage both grass and broadleaf plants.
  • Minimize spraying of foliage, stems, exposed roots, or the trunks of desirable shrubs or trees to avoid harm.
  • Follow the label to avoid damaging the roots of trees and shrubs.

Avoid Wet, Windy, or Hot Weather
Use during favorable weather for best results.

  • Don’t spray when it’s raining or when rain is expected in the next 24 hours.
  • Wind causes spray to drift that can get on you and desired plants.
  • Herbicides may be less effective in hot weather if the target plants are moisture-stressed.
  • Some herbicides can turn into a vapor in hot weather and damage nearby plants.

Protect Pollinators

  • Apply in the early morning or evening when bees are less active.
  • Kill weeds before they flower. Avoid spraying flowering plants.
  • Do not spray on bees or insects.

Storage & Disposal

  • Store in a secure area away from children.
  • Don’t put unused herbicide products in the trash.
  • Never pour down any drain or waterway.
  • Take unused herbicides to a hazardous waste facility.

Call  1-800-CLEANUP (1-800-253-2687) to find out where to dispose of herbicides.

For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call  503-234-3000, email   or visit Metro’s website  

More about:

About Using Pesticides on School Grounds in Oregon

If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management  (Oregon Department of Agriculture).

NEED HELP?

The National Pesticide Information Center (NPIC)  can answer questions about pest control chemicals.
 1-800-858-7378 or npic@ace.orst.edu  

Consider using a licensed pest or weed control company. Learn How to Hire a Pest Control Company.

Your local Extension Specialist in Oregon  and other states  can suggest other methods.

 

Prevent Tansy Ragwort

Tansy ragwort seedlings

Utah State University , Bugwood.org

Look for Tansy Ragwort Seedlings and Rosettes
  • Return to the site after control activities and look for regrowth. Tansy ragwort regrows from seeds in the soil that remain viable for many years.
  • Look for tansy ragwort seedlings like those shown in the photo. Take action as needed.
Gloved hand using metal brush to clean shovel

Weston Miller, Oregon State University

Remove Dirt from Shoes and Equipment
  • After working or traveling in a patch of tansy ragwort, clean your boots and tools. Use a wire brush to remove soil and plant material.
  • If you drive into the tansy ragwort stand, clean your vehicle.
Landscape area with native plants growing densely together

Weston Miller, Oregon State University

Install New Plants
  • Take care of the plants to get them established and suppress tansy ragwort regrowth.
  • Replanting stabilizes the soil surface, shades tansy ragwort seedlings, and creates habitat.
  • A tansy infestation and removal activities may significantly damage a site. There may be few or no remaining desirable plants.
  • Plan for at least 2-3 years of monitoring and maintenance.
  • Your local Extension specialist, soil and water conservation district, or a professional revegetation specialist can suggest strategies for your area.
Fence line in a pasture area showing no tansy ragwort flowering stems on the left of the fence and a tansy ragwort infestation on the right side

Utah State University, Bugwood.org

Pasture Management
  • If you have pasture areas and graze livestock, it is critically important to manage tansy ragwort. All plant parts are poisonous to cattle and horses. Sheep are not susceptible to tansy ragwort poisoning.
  • The best option to control tansy ragwort in pasture areas is to promote a healthy stand of grasses and broadleaf plants. Avoid overgrazing.
  • The photo shows the impact of pasture management on tansy ragwort growth. On the left side of the fence, the pasture is free of tansy ragwort flowering stems. On the right side of the fence, different management over time has led to a tansy ragwort infestation.

Invasive Species Alert

  • Invasives are non-native species that spread aggressively and alter the environment.
  • Controlling unwanted tansy ragwort is costly.
  • Please do your part to control tansy ragwort on property you manage. It can spread beyond your property and affect your neighbors.
static invasive map
Invasive species data @ 2022, iMapInvasives (NatureServe)

Tansy ragwort is very widespread in Oregon. There’s no need to report infestations of it.

Content provided by editor Weston Miller and writer J. Jeremiah Mann. Pesticide safety information edited by Kaci Buhl.

 Peer reviewed by OSU Department of Horticulture.

Photo of Weston Miller

Weston Miller

Project Founder and Content Writer

Weston Miller served as Community and Urban Horticulture faculty for Oregon State University Extension Service for Clackamas, Multnomah, and Washington Counties. Weston is an author for content for this website. He developed funding partnerships with Portland area agencies to initiate and build out the Solve Pest Problems website focused on this goals:

J. Jeremiah Mann

J. Jeremiah Mann

J. Jeremiah Mann completed a Physical Science undergraduate degree at Humboldt State University, and M.S, Ph.D focusing on plant science topics at UC Davis. He went on to work for the Natural Resources Conservation Service and in a leadership position serving a private agricultural technology company. He currently lives in Sacramento California where he consults on pest and property management topics.

Photo of Kaci Buhl

Kaci Buhl

At the state level, I lead the Pesticide Safety Education Program (PSEP). The program hosts live recertification events around the state, serving over 1,000 licensed pesticide applicators each year. We also produce web-based training modules and license-preparation study manuals. Special training for unlicensed pesticide applicators is also available through a grant from the USDA Specialty Crop Block Grant Program. The PSEP at OSU works closely with the Oregon Department of Agriculture's Pesticides Division.

Tansy Ragwort References

Tansy Ragwort  
OSU Extension Service

Tansy Ragwort  
Washington State Noxious Weed Control Board

Tansy Ragwort Identification and Control  
King County, Washington