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Arcata Field Office

Tansy Ragwort (Senecio jacobeae) 

Sunflower family (Asteraceae)
Tansy Ragwort 
Photo courtesy of  J.E. (Jed) and Bonnie McClellan,  California Academy of Sciences 
 
Description: Tansy ragwort is a biennial herb that sometimes reaches more than four feet in height and is highly toxic to livestock. Numerous inch-wide, daisy-like yellow flowers with golden or light brown centers form at the tip of each branch from mid-summer to fall. The plant has a basal rosette of leaves, and the upper parts are branched. Leaves are deeply minutely dissected into irregular segments, leaving the plant a ragged appearance. Leaves or segments are wider than long. 
 
Habitat: It is commonly found in pastures, on roadsides, and in disturbed places. It grows best in light, well drained soils, but can become establish in heavier soils, particularly soils broken up by trampling of frequent cultivation.
 
Distribution: Tansy ragwort is endemic to western Europe and western Asia where it is a weed of minor importance on roadsides and grasslands. It is considered by some authors to be native to the dunes of Holland. In California tansy ragwort is found on the North Coast and into the Klamath and Cascade ranges, also occurring in the Sacramento Valley and San Francisco Bay region.  Tansy ragwort easily outcompetes native and naturalized grasses and forbs. It is estimated to occur on three million acres in western Oregon, where two out of every five acres of pasture are infested. Tansy ragwort seeds are abundant and wind dispersed, but the plant can also reproduce via regeneration of root fragments contained in mud or soil adhering to vehicles.
 
Flowering Period:  Summer blooming; seeds ripen late summer or early fall.
 

Eradication note: Manually pull plants in the spring or early summer when soil moisture is still high to allow more complete root removal.   Be careful though, partially opened flowers continue to set viable seed if sufficient moisture is available in the cut plant. Therefore, plants must be removed from the treated site and buried or burned.

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