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Class B Noxious Weed

Tansy Ragwort
Senecio jacobaea

 

Tansy ragwort flower


Plant family: Asteraceae
Year listed: 1987
Native to: Europe and western Asia

Why is it a noxious weed?
Tansy ragwort is toxic and a threat to livestock and agriculture. Toxic properties are also a threat to humans as possible contaminants to the human food chain. Herbal remedies, honey and contaminated milk are potential sources of toxins in the food.

All plant parts are toxic, with the highest amount of alkaloids in the flowers, followed by the leaves, roots and stems.Tansy ragwort contains several alkaloids, these alkaloids are broken down by liver enzymes during metabolism, they are then considered to be toxic and potentially carcinogenic. Chronic, cumulative poisoning, and irreversible liver damage, including cirrhosis of the liver are the results of ragwort poisoning.

 

How would I identify it?
General Description: Tansy ragwort is a biennial, sometimes perennial herb. As a biennial tansy ragwort spends the first year in the rosette stage, with dark green basal leaves that appear ruffled. During the second year on or two flowering stems emerge.

Leaves:

  • second year leaves are alternate, sessile

Flowers:

  • flat topped clusters
  • each flower has yellow daisy like flowers, with 13 petals

Stems:

  • can reach 1 - 4 feet high

How does it reproduce?
Tansy ragwort usually reproduces by seed, although it can reproduce vegetatively.

Where does it grow?
Tansy ragwort is found roadside, in pastures, fields and cleared forested areas. It is not particular to soil type.

What is the distribution in Washington State?

 

 

 

Click on map to enlarge.
  • Tansy ragwort has been documented throughout Washington. Refer to map for distribution levels in specific counties.
  • Distribution map based on 2003 data.

How do I control it?

General control methods: Small infestations can be controlled manually by pulling up entire plant as long as it is done before flowers begin to seed. Large infestations are better handled by a combination of manual and chemical controls.

Cultural: Good pasture management techniques will prevent infestations.

Herbicide: Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

Mechanical: Mowing is not effective, tansy ragwort can re-sprout if entire plant is not removed. Tansy ragwort becomes a perennial and will regrow every year until plant is removed.

Biological: The ragwort flea beetle (Longitarsus jacobaeae), the ragwort seed fly (Pegohylemyia seneciella) and the cinnabar moth (Tyria jacobaeae) are the biological agents effectively used to control tansy. Unfortunately, the cinnabar moth and the ragwort flea beetle are unable to establish east of the Cascade mountains.

Are there plants that may be confused with Tansy ragwort?
Common St. Johnswort (Hypericum perforatum) and Common tansy (Tanecetum vulgare), Class C noxious weeds in Washington may be mistaken for Tansy ragwort. Common St. Johnswort also is found roadside, has yellow flowers, but it has 5 petals. Common tansy has yellow globes without petals. If you need help with plant identification, contact your county noxious weed coordinator.

For more information
For more information, download our Written Findings.

 

More Photos-Click photo to enlarge
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Tansy ragwort plant. Tansy rosette.

Photo courtesy of Thurston County Noxious Weed Control.

 Tansy infestation.

Photo courtesy of Thurston County Noxious Weed Control.

 Last updated September 08, 2008