Senecio jacobaea |
Senecio integerrimus |
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stinking willie, tansy ragwort |
lambstongue ragwort, mountain butterweed, one-stem butterweed, tall western groundsel, western groundsel |
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Habit | Perennials, 20–80(–100) cm (taprooted or branched caudices surmounting taproots). | Perennials (possibly biennials), (10–)20–70 cm (caudices buttonlike, roots fleshy-fibrous). | ||||||||||||||||
Herbage | sparsely and unevenly tomentose, glabrescent except in leaf axils and among heads. |
arachnose, loosely tomentose, or villous (hairs crisped, jointed), glabrescent. |
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Stems | (often purplish-tinged) usually single, sometimes loosely clustered. |
single. |
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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). |
progressively reduced distally; ± petiolate; blades elliptic, lanceolate, linear, oblanceolate, rounded-deltate, or suborbiculate, 6–25 × 1–6 cm, bases ± tapered or truncate to cordate, margins entire or ± dentate (distal leaves sessile, bractlike). |
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Ray florets | ± 13; corolla laminae 8–12 mm. |
usually ± 8 or ± 13, sometimes 0; corolla laminae 6–15(–20) mm (usually yellow, ochroleucous to white in one variety). |
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Phyllaries | ± 13, 3–4(–5) mm, tips black or greenish. |
usually ± 13 or ± 21, rarely ± 8, (4–)5–12(–15) mm, tips usually black, sometimes green. |
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Calyculi | of 2–6 (inconspicuous) bractlets (less than 2 mm). |
of 1–5+ linear to filiform bractlets (seldom more than 2 mm). |
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Heads | (10–)20–60+ in corymbiform arrays. |
6–20(–40+) in corymbiform arrays (peduncle of terminal head often shorter than others). |
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Cypselae | all sparsely hairy or ray cypselae glabrous. |
usually glabrous, sometimes hirtellous (mostly on angles). |
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2n | = 40. |
= 40, 80. |
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Senecio jacobaea |
Senecio integerrimus |
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Phenology | Flowering spring–early summer(–fall). | |||||||||||||||||
Habitat | Disturbed sites, pastures, roadsides, and waste grounds | |||||||||||||||||
Elevation | 0–1500 m (0–4900 ft) | |||||||||||||||||
Distribution |
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]
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CA; CO; IA; ID; KS; MN; MT; ND; NE; NM; NV; OR; SD; UT; WA; WY; AB; BC; MB; SK
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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.) |
Varieties 5 (5 in the flora). The varieties of Senecio integerrimus are distinguished by morphology and geography. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 20, p. 568. | FNA vol. 20, p. 556. | ||||||||||||||||
Parent taxa | Asteraceae > tribe Senecioneae > Senecio | Asteraceae > tribe Senecioneae > Senecio | ||||||||||||||||
Sibling taxa | ||||||||||||||||||
Subordinate taxa | ||||||||||||||||||
Synonyms | Jacobaea vulgaris | |||||||||||||||||
Name authority | Linnaeus: Sp. Pl. 2: 870. (1753) | Nuttall: Gen. N. Amer. Pl. 2: 165. (1818) | ||||||||||||||||
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