Rhizomes thick. Leaves grayish green, sword-shaped, 20--45 × 0.7--1.5 cm, midvein not obvious. Flowering stems several branched, more than 80 cm × 6--8 mm; spathes green, narrowly ovate to lanceolate, 4.5--5.5 × ca. 1.5 cm, membranous, 1- or 2-flowered. Flowers yellow, 5--5.5 cm in diam.; pedicel 1--3 cm. Perianth tube ca. 1 cm; outer segments ca. 4 × 1 cm; inner segments erect, narrowly oblanceolate, ca. 2.5 cm × 4 mm. Stamens ca. 2.5 cm; anthers yellow. Ovary ca. 2.5 cm × 2 mm. Style branches ca. 3 cm. Capsule ellipsoid-cylindric, 6--9 × 1.5--1.8 cm, 6-ribbed, apex shortly beaked. Seeds maroon-brown, flat, ca. 7 × 5 mm. Fl. May, fr. Jun--Aug.

There is a problem with this species, which was described solely on the basis of fruiting material and has been treated as a synonym of Iris laevigata. It seems that a large, yellow-flowered species indeed occurs in the far east of Russia; however, further study is needed to determine whether or not it is separable from I. pseudacorus Linnaeus.

Damp places near ponds and lakes; near sea level to 300 m. E Heilongjiang, Liaoning [Russia (Far East)].