Invasive Species: Tansy Ragwort

Senecio jacobaea

First noted in Multnomah county in 1922, tansy ragwort is now widespread throughout western Oregon.

Why is it important to control?

Tansy ragwort is poisonous to horses and cattle. It can create dense stands, damaging pastures.

How can you identify it?

Image of a tansy ragwort rosetteImage of tansy ragwort flowering in field
Habitat: Pastures, cropland, meadow, roadsides.
Life Cycle: Biennial
Height: Up to 6 feet
Leaf Description: Leaves are dark green on top, light green below, and deeply lobed.
Fruit & Flower Description: Bright yellow flowers arranged in flat topped clusters.
Bloom Time: July to October

How do you control it?

  • Hand-pulling works for small infestations. Pull May through June.

  • Dispose of all plant material in a tied bag and throw away in trash.

  • Herbicide control:  Oregon State University Extension recommends a triclopyr or glyphosate based herbicide. Take care to avoid drift and be cautious near crops. FOLLOW ALL LABEL DIRECTIONS!

  • The Oregon Department of Agriculture has approved and implemented three biocontrols, a seed head fly, a flea beetle, and a moth. This has had a significant impact on populations, but it needs to be kept in mind that biocontrols are not focused on eradication.

How to report it?

There are various ways you can report this noxious weed.

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