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Tansy Ragwort

Posted by cahnrs.webteam | November 6, 2013

TansyRagwortAlso Known As

ragwort, tansy butterweed, stinking willie, staggerwort


Tansy ragwort is a Class B Noxious Weed. Class B noxious weeds are nonnative species whose distribution is limited to portions of Washington State. In some regions where a Class B species is already abundant, control is decided at the local level, with containment as the primary goal. Tansy ragwort, (Senecio jacobaea L.), native to Europe and western Asia, is a biennial that forms a rosette in its first year of growth; rosettes have dark green basal leaves that are pinnately-lobed and appear ruffled. In the second year, one or more flowering stems bolt and grow to 6 feet tall; stems are erect, purplish-red and branched near the top. Leaves on the coarse flowering stems arealternate, equally distributed and 2–3 times pinnately lobed (its leaves distinguish tansy ragwort from other Senecio species). While the rosette and basal leaves are stalked, stem leaves are not. Flowers are produced from late summer to fall. Flowering heads are numerous and small (unlike the single large head of other species) and occur in flat-topped clusters. The bright yellow, daisy-like flowers are each composed of a disc flower surrounded by 10–15 ray (petal) flowers. A single plant can produce over 150,000 seeds, which remain viable for many years depending on soil depth. Tansy ragwort plants have taproots and fibrous root systems. Reproduction is primarily by seed, although new plants can form vegetatively from crown buds or root fragments. Disturbance or environmental influences can cause a plant to remain in the rosette stage (becoming a short-lived perennial) until it eventually goes to seed and then dies.

Tansy ragwort contains alkaloids that are toxic to livestock, particularly cattle and horses and less so in sheep and goats. In susceptible animals, the toxins cumulatively cause irreversible liver damage. The toxic properties of tansy ragwort continue after the plant is cut or baled in hay. Human poisoning can also occur.

Tansy ragwort is commonly found in decadent pastures, waste areas, forest openings and alongside roads. Uncontrolled infestations can result in lost production capacity, increased management costs and livestock losses.

Control Methods

Cultural: Competitive vegetation will discourage tansy ragwort from invading or re-invading and should be maintained.
Mechanical/physical control: Because of tansy ragwort’s ability to regenerate from root fragments, care must be taken when attempting physical or mechanical control methods. Hand pulling of small infestations is effective if the entire root mass is removed with each plant. Moist soil will simplify the task. If removal occurs post-bloom, the entire plant should be bagged and properly disposed of. Mowing is not recommended as it merely stimulates vegetative growth and leaves root systems intact.

Chemical: Dicamba, aminopyralid, 2,4-D or picloram (as well as dicamba/pilcoram + 2,4-D)
have been effectively used to control tansy ragwort. Herbicides are best applied when the plant is actively growing during the rosette stage. While 2,4-D is best for new growth, dicamba and dicamba + 2,4-D can be used on more mature plants. Picloram should be used only in dry, interior zones withoutclose proximity to water sources.
Caution: Because spraying increases tansy ragwort’s palatability, if the sprayed area is to be grazed, grazing should be delayed for 3–4 weeks to avoid poisoning.

More information can be found in the PNW Weed Management Handbook

  • Use pesticides with care.
  • Apply them only to plants, animals, or sites listed on the label.
  • When mixing and applying pesticides, follow all label precautions to protect yourself and others around you.
  • It is a violation of the law to disregard label directions.
  • Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.

Biological: Use of biological control agents should be considered for areas that are difficult to otherwise manage. The cinnabar moth (Tyria jacobaeae) is favored because its larvae feed on the leaves, buds, and flowers of tansy ragwort. Other insect agents include a seed head fly (Hylemyaseneciella) and the ragwort flea beetle (Longitarsus jacobaeae). The cinnabar moth and the ragwort flea beetle may be unable to establish, depending on geographic location.

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