Ecology and management of tansy ragwort (Senecio jacobaea L.)

Abstract

Tansy ragwort, a member of the Asteraceae taxonomic family, is a large biennial or short-lived perennial herb native to and widespread throughout Europe and Asia. Stems can grow to a height of 5.5 feet (1.75 meters), with the lower half simple and the upper half many-branched at the inflorescence. Reproductive stems produce up to 2,500 bright golden-yellow flowers. Capitula (flowerheads) arranged in 20-60 flat-topped, dense corymbs per plant are composed of ray and disc florets; both produce achenes containing a single seed. Rosettes formed of distinctive pinnately-lobed leaves attain a diameter of up to 1.5 feet (0.5 meter). First reported in Montana in 1979 in Mineral County, tansy ragwort has since spread into Flathead, Lincoln, and Sanders Counties. Soils with medium to light textures in areas receiving sufficient rainfall (34 inches or 860 millimeters/year) readily support populations of tansy ragwort. This species is a troublesome weed in decadent pastures, waste areas, clear-cuts and along roadsides. Tansy ragwort produces pyrrolizidine alkaloids - these can be lethal if ingested by cattle, horses and deer, but are less toxic to sheep and goats. Unchecked infestations can result in significant livestock losses, decreased pasture yields and increased management costs (see Figure 1).

Citation

Jacobs, Jim; Sing, Sharlene. 2009. Ecology and management of tansy ragwort (Senecio jacobaea L.). Invasive Species Technical Note MT-24. Bozeman, MT: U.S. Department of Agriculture, Natural Resources Conservation Service. 13 p.