Arum ringens Thunberg, Trans. Linn. Soc. London 2: 337. 1794; Arisaema arisanense Hayata; A. taihokense Hosokawa.

Plants dioecious. Tuber depressed globose, 2-5 cm in diam. Cataphylls greenish to purplish. Leaves 2; petiole greenish and unmarked, 15-35 cm, proximal 1/3 sheathing into pseudostem; leaf blade 3-foliolate; leaflets sessile, glaucous abaxially, green adaxially, margin entire, apex long acuminate with a tail ca. 2 cm; central leaflet ovate-lanceolate to rhombic-elliptic, 16-22 × more than 10 cm, base cuneate; lateral leaflets obliquely ovate, 15-18 × 10-13 cm, apex filiform-caudate. Peduncle greenish, unmarked, shorter than petioles, to 25 cm. Spathe yellowish green to green; tube yellowish green to green outside, purplish red with white or pale yellowish green striations inside, cylindric, gradually opening to an auriculate throat, 3-3.5 × 1-2 cm; limb concave and incurved, saccate, apex caudate. Spadix unisexual; female zone conic, ca. 1.8 × 1.2 cm; ovary greenish, obovoid; stigma subsessile, pilose; male zone sessile, cylindric, ca. 1.5 cm × 8 mm; synandria subsessile; anthers 2 or 3; thecae globose, dehiscing by an apical pore. Appendix erect, white, narrowly conic, 2-6 cm × 5-10 mm, base truncate and stipitate, apex obtuse; stipe 3-10 mm. Infructescence erect. Fl. Apr. 2n = 28.

Low elevations. Jiangsu, Taiwan, Zhejiang [Japan, Korea].