Perennial herbs with short rhizomes. Stems simple, ascending, striate, 15-75 cm tall, green, glabrous or subglabrous apically, purplish green to dark purple and increasingly densely villous toward base. Leaves dark green on upper surface, dark purple to greenish purple on lower surface, thick chartaceous, highly variable in shape, lateral veins 3-5-paired. Lower and middle cauline leaves triangular-ovate or lanceolate, 3-9×2-5 cm, lower surface villous, upper surface subglabrous, apex acute-mucronate, base obtuse, truncate or cordate, margins mucronate-serrate, dentate, coarsely dentate or cleft, sometimes with 1 or 2 distinct, ovate or obovate basal appendages; petiole 3-8 cm long, villous. Upper cauline leaves lanceolate, linear-lanceolate to linear, (3-)4-8×(0.3-)1-2 cm, apex acute or acuminate, base obtuse or attenuate, margins mucronate, subentire, remotely dentate or irregularly lobed, petiole 1-2 cm long, or leaves near base of inflorescence subsessile, villous. Heads 3-3.5 cm across, bracteate, solitary, or to ca. 20 in loose corymbs; peduncle 2.5-6(-12) cm long, slender, subglabrous or sparingly puberulous, bracteate; bracteoles 2-5, remote, ascending, linear, 1-4.5 mm long. Involucre cylindric, ca. 8 mm long, 5-6 mm across; bracts 2-seriate; outer bracts calyculate, 4 or 5, linear, 3-3.5×0.3-0.5 mm; inner bracts green, tinged purple at apex, ca. 20, subequal, lance-linear, 6.5-8×1.2-1.5 mm, apex acuminate, base obtuse, margins membranaceous, 1-nerved, glabrous to sparsely pubescent. Ray florets 8-12, corolla yellow, ca. 15-17 mm long, ligules 10-12 mm long, 4-veined, tube ca. 5 mm long; disc florets ca. 40, yellow, funnelform, ca. 6.5 mm long, apically papillose, otherwise glabrous, limb 3.3-3.5 mm long, tube 3-3.2 mm long, 5-lobed, lobes ca. 1.3-1.5×0.7-0.8 mm, acute. Anthers 1.8-2.2 mm long, obtuse at base, filaments ca. 1.8 mm long; appendages ovate, apex obtuse, ca. 0.25 mm long; anther collars slightly dilated at base, 0.3 mm long. Style branches ca. 1.2 mm long, apex truncate, papillate. Achenes brownish, cylindric, slightly narrowed at both ends, 3-4 mm long, 0.6-0.8 mm thick, minutely appressed hairy; pappus white, in 1 series, 4-5.5 mm long.
HUALIEN: Taroko Natl. Park, Yenhai Forest Road, Peng 15456 (Holotype!); Chingshuishan, Leu 1809.
Endemic and rare, known only in metamorphosed limestone mountains in Taroko National Park in eastern Taiwan, in semishaded to open rocky ridges with abundant herbaceous and dwarf scrub vegetation. Senecio tarokoensis is somewhat similar to S. fukienensis Ling ex C. Jeffrey & Y. L. Chen of southern China, but differs in its simple stems, triangular-ovate or lanceolate lower and middle cauline leaves (vs. oblong-elliptic or narrowly so), long petiole (vs. auriculate and amplexicaul leaves) and ray florets more numerous (8-12 vs. 7-8) with much longer corollas (15-17 mm vs. 7.5-9.5 mm). It is also the largest flowered species of Senecio in Taiwan.
