Description from Flora of China
Lactuca morii Hayata; L. sonchus H. Léveillé & Vaniot; Pterocypsela formosana (Maximowicz) C. Shih; P. sonchus (H. Léveillé & Vaniot) C. Shih.
Herbs 0.5-1.5 m tall, annual or ?perennial. Roots ramose. Stem solitary, erect, loosely branched apically, ± hirsute, glabrescent. Lower and middle stem leaves with narrow petiole-like amplexicaul basal portion to 5 cm or with conspicuously expanded and semiamplexicaul base; leaf blade elliptic, lanceolate, or oblanceolate, 8-18 × 4-8 cm, hirsute, main rib echinulate, undivided and with coarsely dentate margin or pinnatifid with 2-5 pairs of elliptic to broadly falcate lateral lobes, faintly to strongly dentate on margin, and a lanceolate or triangular terminal lobe. Upper stem leaves similar to middle stem leaves, margin mostly ± entire. Synflorescence loosely corymbose, with ca. 10 to many capitula. Capitula with usually 25-30 florets. Involucre cylindric, 1-1.1 cm at anthesis, to 1.8 × 0.8 cm in fruit. Phyllaries acute to acuminate at apex; outer phyllaries broadly obovate to lanceolate, longest ca. 8 × 1-2 mm; inner phyllaries 8. Florets yellow. Achene 4.5-6.5 mm; body reddish brown, dark brown, or blackish brown, ellipsoid, compressed, broadly winged, 2-2.3 mm wide, with 1 prominent rib on either side, apically contracted into a usually pale to greenish filiform 2-3.5 mm beak. Pappus 7-8 mm, caducous. Fl. and fr. Apr-Nov. 2n = 18*.
Lactuca formosana is similar to L. raddeana, L. triangulata, and L. indica, and the leaf shape of L. formosana in mainland China shows some variation. Instead of the typically lyrate-pinnatifid leaves with irregularly incised to dentate margin, plants sometimes have narrow, weakly pinnatifid leaves more similar to those of L. indica. However, usually both species can be distinguished by the shape of the synflorescence (corymbiform in L. formosana, paniculiform to racemiform-paniculiform in L. indica) and the indumentum of stem and leaves (hirsute and with echinulate main rib in L. formosana, glabrous in L. indica). Conspicuous, occasionally occurring plants with all or most leaves undivided, as are sometimes the upper stem leaves in usually pinnately lobed plants, have been treated as a separate species, Lactuca sonchus or Pterocypsela sonchus, respectively (e.g., FRPS 80(1): 231. 1997), but are here considered as a mere form of L. formosana, easily recognizable by the distinctive long beak of this species.
● Grasslands on mountain slopes and in valleys, thickets or forests on mountain slopes, fields, along trails; 100-2000 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Ningxia, Shaanxi, Sichuan, Taiwan, Yunnan, Zhejiang.