51. Senecio jacobaea Linnaeus, Sp. Pl. 2: 870. 1753.
新疆千里光 xin jiang qian li guang
Jacobaea vulgaris Gaertner; Senecio foliosus Candolle; S. jacobaea subsp. nudus (Weston) Soják; S. jacobaea var. nudus Weston; S. jacobaeoides Willkomm.
Herbs, biennial, rhizomatous. Stems solitary or 2- or 3-fasciculate, erect, 30-70(-100) cm tall, branching into synflorescence, at first arachnoid, glabrescent to subglabrous. Basal leaves withered and usually shed by anthesis; lower stem leaf petioles 3-4 cm, base expanded; blade oblong-obovate, to 15 × 3-4 cm, papery, abaxially sparsely arachnoid, adaxially glabrous, obtusely dentate or lyrate-pinnatifid, with large terminal lobe and 6-8 smaller, oblong-lanceolate lateral lobes. Median stem leaves rather crowded, sessile, pinnatisect, 8-10 × 1-4 cm, base lacerate-auriculate, with indistinct terminal lobe and linear-lanceolate to linear, obtuse, dentate or subentire somewhat ascending lateral lobes. Upper leaves similar but smaller, with oblong or linear-oblong lateral lobes. Capitula radiate, numerous, arranged in terminal compound corymbs; peduncles 0.5-1.5 cm, sparsely arachnoid, bracteate, with 2 or 3 linear bracteoles. Involucres broadly campanulate or hemispheric, 5-6 × 5-7 mm, calyculate; bracts of calyculus 2-6, linear, 2-3 mm, apically acuminate; phyllaries ca. 13, oblong-lanceolate, ca. 1.5 mm, herbaceous, subglabrous, margin scarious, apically acuminate and puberulent. Ray florets 12-15; corolla tube 2.5-3 mm; lamina yellow, oblong, 8-10 × 2-2.5 mm, 4-veined, apically 3-denticulate. Disk florets many; corolla yellow, ca. 6 mm, with ca. 2 mm tube and funnelform limb; lobes triangular-ovate, ca. 0.5 mm. Anthers ca. 2.5 mm, basally distinctly subacutely auriculate, appendages ovate-lanceolate; antheropodia rather short, markedly dilated in lower half. Style branches ca. 1 mm. Achenes cylindric, ca. 2 mm, pubescent in disk florets, longer and glabrous or rarely pubescent in ray florets. Pappus white, ca. 6 mm, persistent in disk florets, readily deciduous in ray florets. Fl. May-Jul. 2n = 40, 80.
Meadows, lax forests; 500-2000 m. Jiangsu, Xinjiang [Kazakhstan, Kyrgyzstan, Mongolia, Russia (Siberia), Tajikistan, Uzbekistan; Europe].
The occurrence of Senecio jacobaea in Jiangsu is presumably the result of an introduction; this species was first recorded for this province by Kitamura.