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Tansy ragwort is an invasive introduced species from Europe that is now found in eastern and western North America, but is absent from the prairies and midwestern states (United States: CA, ID, IL, IN, MA, ME, MI, MT, NJ, NY, OR, PA, WA, WY; Canada: BC, MB, NB, NF, NS, ON, PE, QC) (USDA 2010). It is poisonous to livestock (BC Ministry of Agriculture 2009). Biological control methods have been applied to it, including the introduction of the cinnabar moth (tiger moth) (Tyria jacobaeae) to North America, a species which feeds exclusively on tansy ragwort. In our region, tansy ragwort can be confused with common tansy (Tanacetum vulgare), however, tansy ragwort has yellow ray petals, while common tansy lacks ray petals. Tansy ragwort was first recorded in British Columbia at Nanaimo in 1950 (BC Ministry of Agriculture 2009). Flora North America Online provides a detailed description for this species. Read more about this species in BC.
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General: Biennial or short-lived perennial herb from a poorly-developed to evident taproot; stems erect, solitary or several, branched above, sparsely to densely white woolly-hairy, 0.2-1 m tall.
Leaves: Basal leaves oblanceolate, stalked, 4-20 cm long including the stalk, 2-6 cm wide, mostly 2-3 times pinnately cut, thinly woolly-hairy when young but usually glabrous by flowering time; stem leaves similar, progressively reduced upwards, becoming unstalked.
Flowers: Heads with ray and disk flowers, several to numerous in clusters; involucres 2-5 mm tall; involucral bracts oblanceolate, with long-pointed, usually black tips, hairless to sparsely woolly-hairy, margins translucent; bracteoles few, black-tipped; ray flowers yellow, 4-10 mm long; disk flowers yellow.
Fruits: Achenes oblong, nerved, those of the disk flowers minutely coarse-hairy, those of the ray flowers glabrous; pappus of white hairlike bristles.
Tansy ragwort is considered an emerging invasive species in the Vancouver region by the Greater Vancouver Invasive Plant Council (2009). An emerging invasive species is defined by them as species "currently found in isolated, sparse populations but rapidly expanding their range within the region". It is listed as one of the top fourteen species of concern by the Coastal Invasive Plant Council. Visit their web site.
Ecological Framework for Senecio jacobaea
The table below shows the species-specific information calculated from original data (BEC database) provided by the BC Ministry of Forests and Range. (Updated August, 2013)
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2017. E-Flora BC:
Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for
Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
26/02/2017 6:35:30 AM
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