Erect biennial herbs, sometimes diffuse and decumbent, stems terete, 20-60 cm tall, well branched from lower part of stem, terminating in 1-few heads, glabrous. Radical leaves rosulate, oblong-spatulate, 8-15 cm long, 3-5.5 cm wide, apex round, base cuneate, margins entire, ciliate, nearly glabrous on both surfaces, withered at anthesis. Cauline leaves green, thin, elliptic-lanceolate or obovate, apex round or obtuse, base narrowed, sessile, 4.5-5.5 cm long, 13-23 mm wide, hispid on veins on lower surface, margins entire, ciliate; usually bimodal in size and shape, leaves below lowest branch larger, leaves on branches smaller, elliptic-lanceolate to oblong-lanceolate, 2-3 cm long, 6-10 mm wide. Heads many, 2.5-3.5 cm across, peduncle 2-3 cm long, often solitary, terminating branches, in loose corymbs. Involucre hemispheric or bowl-shaped, 7-10 mm long, 12-16 mm broad, bracts green, herbaceous, 2 or 3 seriate, subequal, linear lanceolate or subulate, entire, acuminate to attenuate-acuminate, 4.5-7.5 mm long, 1-1.7 mm wide, sparsely hirsute outside, margins ciliate. Ray florets 15-22 in 1 or 2 series or sometimes lacking, when present ligules white, 8.5-12 mm long, 2-3 mm wide, tube 1 mm long. Disc florets 4-4.5 mm long, unequally 5-lobed. Pappus dimorphic, that of ray florets white, 0.5-1 mm long, forming a crown, that of disc florets reddish, 3-4 mm long. Achenes brown, obovate, compressed, 2.5-3 mm long, 1.5-2 mm broad, finely sericeous, sparsely glandular punctate apically. Fl. Nov-Jun. Chromosome number, 2n = 36 (Peng & Hsu, 1978); 2n = 54 (Gu, Cathaya 1: 3. 1989).

TAIPEI: Keelung, Faurie 205; Tamura, Shimizu & Kao 20005. ILAN: Suao, Nagasawa s.n. 1907.

Endemic; northern coast of Taiwan.

Aster oldhamii differs from A. hispidus by its dimorphic leaves, with the larger leaves below the lowest branch and smaller leaves on the upper part. Ray florets are lacking in some individuals of A. oldhamii.