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tansy ragwort (Senecio jacobaea)
ODA rating: B and T
Description
Biennial or short-lived perennial; blooms midsummer to fall. Grows 1 1/2 – 6 feet tall. Leaves dark green, deeply lobed. Numerous seed heads, each with multiple, yellow, multi-rayed flowers. Reproduces by seed only.
Impact
Prolific in pastures, clearcuts, and disturbed roadside areas. Tansy ragwort’s seeds can lay dormant in the soil for 15 years. Once considered Western Oregon's most serious noxious weed, biological controls have reduced the severity of outbreaks below economic threshold levels.
Click on image to view larger photo.
Image courtesy of Eric Coombs, Oregon Dept. of Agriculture.
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Image courtesy of Weed Science Society of America.
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Image courtesy of Eric Coombs, Oregon Dept. of Agriculture.
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Known hazards
Tansy ragwort is toxic to cattle and horses, causing irreversible liver damage.
Distribution in Oregon
The first documented site in Oregon was 1922 in Multnomah County
Map legend
Yellow: limited distribution
Red: abundant
Grey: not known to be present
Biological controls
Three biological control agents, a seed head fly, a flea beetle and a moth, have been approved for release and are established in Western Oregon. Eastern Oregon plant populations are still sparse and tansy ragwort on the East side of Oregon is being managed for eradication and containment rather than biological control.
Informational Links
WeedMapper
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