Invasive Alerts- Tansy Ragwort
:: Tansy Ragwort (Senecio jacobaea)
May 2003
:: Hydrilla (Hydrilla verticillata)
November 2001
:: Plant Diseases/Pests

May 2003
Tansy Ragwort
(Senecio jacobaea)
Stinking willie, tansy butterweed

Downloadable Alert Poster (with IPANE contact information)
Downloadable Alert Poster (add your own contact information)

Tansy ragwort (Senecio jacobaea L.) has been discovered in Worcester county, Massachusetts and Hancock county, Maine. Previously, this species was only known in Essex county, Massachusetts and Cumberland county, Maine.

This highly invasive plant contains pyrrolizidine alkaloids, which are toxic to livestock and humans if ingested. A single S. jacobaea plant can produce up to 150,000 seeds, which are easily dispersed by wind, livestock and humans, and remain viable for 6 years. S. jacobaea can also reproduce vegetatively, which increases its reproductive success.

S. jacobaea can be found in forested and riparian areas, full sun or partial shade pastures, roadsides, vacant lots and other disturbed sites. It grows best on well-drained soils in cool, moist climates, and is least tolerant of high water tables or acidic soils. Senecio species are easily recognized by their flower clusters, which are comprised of small bright yellow flowers with 13 petals. S. jacobaea is distinguished from other Senecio species by its perennial nature, woody stem base and flowering period from July to September. Its alternate leaves are dark green on top and whitish-green on the underside, and may be glabrous to lightly covered with long hairs, especially on the lower leaf surface and new growth. The leaf edges are deeply lobed with a ruffled appearance. This species can grow up to 3 feet tall in New England and produces tiny seeds that can be glabrous or pubescent. Seedlings are rosettes of deeply lobed, ragged leaves up to 9 in. (23cm) long.

Early detection and prevention will greatly reduce the infestation of S. jacobaea. Small, isolated populations can be easily eradicated by hand-pulling. Prevention could include washing clothing, shoes, animals and vehicles that have come in contact with the fruiting plants.

Mature, larger stands can be controlled with a combination of mechanical means and herbicides. Plants should be pulled from May to June (i.e., after they bolt but before they flower). When mature plants are pulled, small rosettes usually remain and must be dug up completely, so that root parts cannot re-sprout. Herbicides can also be used to control S. jacobaea, and are most effective when used on grassy areas and applied in early spring. Mowing is not an effective means of control, since the plant can re-sprout and flower in the same season, however, tilling infested areas has been shown as an effective means of mechanical control. Two biological control agents, the cinnabar moth (Tyria jacobaeae) and the ragwort flea beetle (Longitarsus jacobaeae) have been introduced on the West coast for biocontrol of S. jacobaea.

Burrill, L.C., R.H. Callinghan, R. Parker, E. Coombs, and H. Radtke. 2002. Tansy
Ragwort (Senecio jacobaea L.). Forage Information System. viewed 1 November.

Garvin, J. 2002. Tansy Ragwort. California Department of Food and Agriculture:
. viewed 1 November.

King County Noxious Weed Control Program. 2002. Best Management Practices Tansy
(Senecio jacobaea). viewed 1 November.

USDA, NRCS. 2002. The Plants Database, Version 3.5.
National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Additional Links

Idaho One Plant

Nature Conservancy

Nova Scotia Department of Agriculture and Fisheries

Sawtooth National Forest—Idaho

Tansy Ragwort Poisoning in Newfoundland

USDA—Poisonous Plants Research Laboratory

Washington State Noxious Weed Control Board—Coloring Book