The reed lily is a perennial emergent aquatic plant, herbaceous. The plant height ranges from 100-250 cm (medium-sized plants, with leaf surface height of 60-150 cm, but the flower stems are slender and often exceed the leaf surface by 50-100 cm); the leaves are basal, with 4-6 leaves; the petioles are long, about 40-80 cm, sheathed at the base, slightly swollen at the base, with the top and base of the petiole reddish-brown or pale yellow-brown; the leaf blades are ovate-lanceolate to elongate, 20-50 cm long, 10-20 cm wide, hard and papery, pale gray-green, with purple edges, entire; the leaf back is covered with white powder, and the leaf underside has sparse soft hairs. The leaf base is rounded and obtuse, while the leaf tip is acute; the transverse parallel leaf veins.
Inflorescence paniculate, borne at the apex of the rachis emerging from the sheath; involucral bracts numerous, semi-closed, easily shed when in flower; small flowers purple-red, 2-3 flowers enclosed by two small bracts, closely sessile on the receptacle; usually only one small flower develops into a fruit, rarely two or three do so. Small bracts 0.8-1.5 cm, concave, coriaceous, glabrous on the back, with a waxy layer on the surface, and white pubescent on the ventral side. Sepals 1.5-2.5 mm, purple; lateral staminodes petaloid, base white to light purple, apex and margin dark purple, 1.2-1.5 cm long, about 0.6 cm wide; corolla tube short-columnar, pale purple, labellum pouch-shaped, upper part dark purple, lower part pale purple. Capsule nearly globose or ovoid-globose, longitudinal and transverse diameters about 0.9-1.2 to 0.8-1.1 cm, pericarp light green,开裂 at the apex when mature. Mature seeds brownish, rough textured, with aril, hilum somewhat prominent. 2n = 12.
The reed lily has a clump-like rhizome, which sprouts and grows into separate plants. Its root system is particularly robust, with adventitious roots densely distributed on the rhizome. On a 10-cm rhizome, there can be 70-90 adventitious roots, which can grow up to 50-90 cm long. The roots have lateral roots, with the upper lateral roots especially well-developed. The underground root and rhizome of the reed lily have a substantial volume, comparable to the aboveground portion.