Iris ensata var. spontanea (Makino) Nakai; I. kaempferi Siebold ex Lemaire; I. kaempferi var. spontanea Makino; I. laevigata Fischer var. kaempferi (Siebold ex Lemaire) Maximowicz.

Rhizomes creeping, thick. Leaves linear, 30--80 cm × 5--12 mm, midvein distinct on both surfaces, apex acuminate. Flowering stems 25--100 cm, solid, 1--3-leaved; spathes 3, lanceolate, unequal, 4.5--7.5 × 0.8--1.2 cm, leathery, 2-flowered, veins distinct, raised, basal spathe shorter, apex usually acute, apical spathe longer, apex usually obtuse. Flowers dark reddish purple, 9--10 cm in diam.; pedicel 1.5--3.5 cm. Perianth tube 1.5--2 cm; outer segments obovate, mottled yellow at center, 7--8.5 × 3--3.5 cm; inner segments erect, narrowly lanceolate, ca. 5 cm × 5--6 mm. Stamens ca. 3.5 cm; anthers purple. Ovary cylindric, 1.5--2 cm × ca. 3 mm. Style branches purple, ca. 5 cm × 7--10 mm. Capsule ellipsoid, 4.5--5.5 × 1.5--1.8 cm, 6-ribbed, apex shortly beaked. Seeds maroon-brown, semiorbicular, flat. Fl. Jun--Jul, fr. Aug--Sep. 2 n = 24*.

Iris ensata is commonly cultivated in China in a wide range of forms, which have been included under var. hortensis Makino & Nemoto.

Damp areas along rivers and near lakes; 400--1700 m. Heilongjiang, Jilin, Liaoning, Shandong, Zhejiang [Japan, Korea, Russia].