Miller, Gard. Dict., ed. 8 Iris no. 9. 1768.
Rhizomes sparingly short-branched, forming dense clumps, 1—1.5 cm diam., hard, with old leaf bases at nodes; roots fleshy. Stems slightly flattened, with 1—2 short branches, solid, 4—12 dm. Leaves: basal erect, blade with slight spiral twist and central ridge, 3.5—8 dm × 1—2 cm, stiff, harsh, fibrous, glaucous; cauline 2—3, 1—2 subtending floral clusters, blade reduced. Inflorescence units clustered, 2—4-flowered; spathes white, 3—5 cm, subequal, papery. Flowers: perianth white; floral tube funnelform, 1—2.5 cm; sepals spreading and arching downward, with large yellow basal area, broadly orbicular, 8—10 × 3—6 cm, apex rounded, deeply emarginate; petals white, spatulate, 4—6 × 1—1.5 cm, base gradually attenuate, apex emarginate; ovary triangular in cross section with 2 ribs at each angle, 2—2.5 cm; style white, with parallel sides, 4—5 cm, crests erect, triangular, 1—2 cm; stigmas 2-lobed; pedicel 2.5—7.5 cm. Capsules ovoid to oblong-elliptic, triangular in cross section, each angle 2-ribbed, 4—5 × 2—2.5 cm. Seeds in 2 rows per locule, white, flattened or wedge-shaped, 4—5 mm, papery, wrinkled. 2n = 40.
Flowering May--Jul. Persisting after cultivation or discarded along roadsides; introduced; Calif., Conn., Mo.; expected elsewhere; Greece, Turkey.