WSU Extension

Hortsense

Weeds : Tansy ragwort : Senecio jacobaea
(revision date: 2/12/2019)

Family: Asteraceae (Compositae)
Cycle: Biennial
Plant Type: Broadleaf

Use Integrated Pest Management (IPM) for successful weed management.

Biology
Tansy ragwort is a biennial or short-lived perennial spreading by seeds. In lawns, regular mowing may maintain it in a non-flowering perennial form. First-year rosettes have a cluster of basal leaves. Second-year plants grow upright to two to four feet. Leaf shape varies greatly, with some leaves deeply lobed the full length of the blade and others lobed mainly near the base. The lobes are round-tipped and give the leaf a ragged or ruffled appearance. Leaves are alternate and dark green above and whitish-green beneath. The stout stems may be branched, or several stems may emerge from the base of the plant. Yellow flower heads are borne at the top of the branches in flat-topped clusters. Each 1/2-inch flower head has a yellow center and a fringe of 10 to 15 long "petals" or ray flowers at the edge. Common tansy (Tanacetum vulgare), often mistaken for tansy ragwort, has fern-like leaves and button-like flower heads that lack ray flowers. SPECIAL INFORMATION: Tansy ragwort is toxic to livestock in both fresh and dried forms. While animals typically do not graze on it, they may be unable to avoid it in dried hay. Ingestion causes irreversible liver damage and may taint milk and honey. In WASHINGTON, it is designated as a Class 'B' noxious weed. Control may be required in your county. In OREGON, it is designated as a Class 'B' noxious weed, as well as a target (T) weed. Target weeds are considered a priority weed for statewide management. Control of target species may be required in your county. Consult your local Noxious Weed Control Board for more information.
Habitat
Tansy ragwort is found primarily west of the Cascades. It grows in pastures, waste areas, and disturbed sites. It is not usually a problem in maintained lawn and turfgrass.

Management Options

Non-Chemical Management
  • Cultivation (rototilling or hoeing) will effectively eliminate plants.
  • Careful digging is useful to manage weed populations. However, digging can carry undesirable weed seed to the surface and foster further germination.
Select non-chemical management options as your first choice!

Chemical Management

Apply according to label directions. Glyphosate products should be applied as spot treatments only! NOTE: Some ingredients listed here are only available in combination. Read the label carefully on combination products to make sure the product is suitable for your specific situation.

Landscape areas
  • glyphosate
  • dichlobenil
Turf areas
  • 2,4-D + MCPP + dicamba
Bare ground areas
  • glyphosate
Images
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Caption: Tansy ragwort
Photo by: T. W. Miller
Caption: Tansy ragwort flowers
Photo by: T.A. Bertram
Caption: Tansy ragwort rosettes
Photo by: T.W. Miller
Caption: Tansy ragwort flowers
Photo by: T.A. Bertram
Caption: Tansy ragwort in spring
Photo by: T.A. Bertram
Caption: Tansy ragwort rosette
Photo by: T. W. Miller