Flora of North America species comparison

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Senecio jacobaea

stinking willie, tansy ragwort
Habit Perennials, 20–80(–100) cm (taprooted or branched caudices surmounting taproots).
Herbage

sparsely and unevenly tomentose, glabrescent except in leaf axils and among heads.
Stems

(often purplish-tinged) usually single, sometimes loosely clustered.
Leaves

± evenly distributed (basal often withering before flowering); petiolate (sometimes obscurely);

blades ovate to broadly ovate (usually 1–3-pinnate, lobes mostly obovate to spatulate), (4–)7–20(–30) × (1–)2–5(–12) cm, bases usually tapered, ultimate margins dentate (distal leaves similar, smaller).
Ray florets

± 13;

corolla laminae 8–12 mm.
Phyllaries

± 13, 3–4(–5) mm, tips black or greenish.
Calyculi

of 2–6 (inconspicuous) bractlets (less than 2 mm).
Heads

(10–)20–60+ in corymbiform arrays.
Cypselae

all sparsely hairy or ray cypselae glabrous.
2n

= 40.

Senecio jacobaea
Phenology Flowering spring–early summer(–fall).
Habitat Disturbed sites, pastures, roadsides, and waste grounds
Elevation 0–1500 m (0–4900 ft)
Distribution
from FNA
CA; ID; IL; MA; ME; MI; MT; NJ; NY; OR; PA; WA; BC; NB; NF; NS; ON; PE; QC; SPM; Europe [Introduced in North America]
[WildflowerSearch map]
Discussion

Senecio jacobaea is a weed introduced from Europe and now well established in places of cool, damp summers. It is toxic to livestock and legally noxious in most states and provinces where it occurs.

The Russian botanist E. Wiebe (2000) resuscitated Jacobaea for plants that are treated here as Senecio jacobaea, S. erucifolius, and S. cannabifolius. Phylogenetic studies may confirm the utility of recognizing Jacobaea as a distinct genus; to do so here would be premature.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 20, p. 568.
Parent taxa Asteraceae > tribe Senecioneae > Senecio
Sibling taxa
S. actinella, S. amplectens, S. ampullaceus, S. aphanactis, S. arizonicus, S. aronicoides, S. astephanus, S. atratus, S. bigelovii, S. blochmaniae, S. californicus, S. cannabifolius, S. clarkianus, S. crassulus, S. elegans, S. elmeri, S. eremophilus, S. ertterae, S. erucifolius, S. flaccidus, S. fremontii, S. hydrophiloides, S. hydrophilus, S. integerrimus, S. lemmonii, S. lugens, S. lyonii, S. megacephalus, S. mohavensis, S. multidentatus, S. neowebsteri, S. parryi, S. pattersonensis, S. pseudoarnica, S. pudicus, S. quaylei, S. rapifolius, S. riddellii, S. sacramentanus, S. scorzonella, S. serra, S. sheldonensis, S. soldanella, S. spartioides, S. sphaerocephalus, S. spribillei, S. squalidus, S. sylvaticus, S. taraxacoides, S. triangularis, S. viscosus, S. vulgaris, S. warnockii, S. wootonii
Synonyms Jacobaea vulgaris
Name authority Linnaeus: Sp. Pl. 2: 870. (1753)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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