The reed palm is a perennial emergent aquatic plant, herbaceous. The plant height ranges from 100 to 250 centimeters (medium-sized plant, with leaf surface height from 60 to 150 centimeters, but the flower spathes are slender and often exceed the leaf surface by 50 to 100 centimeters); the leaves are basal, with 4 to 6 leaves; the petioles are long, about 40 to 80 centimeters, lower part sheath-like, 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 elongated, 20 to 50 centimeters long, 10 to 20 centimeters wide, hard papery, pale gray-green, with purple edges, entire; the lower surface of the leaf is covered with white powder, and the upper surface has sparse soft hairs. The leaf base is rounded and obtuse, while the leaf tip is acute; the transverse parallel leaf veins.

Compound panicle, borne at the top of the raceme stem emerging from the sheath; involucral bracts numerous, semi-closed, easily falling off during flowering; small flowers purple-red, 2-3 flowers enclosed by two small bracts, closely attached to the receptacle; usually only one flower develops into a fruit, rarely two or three do so. Small bracts 0.8-1.5 cm, concave, coriaceous, hairless on the back, with a waxy layer on the surface and white soft hairs on the ventral side. Sepals 1.5-2.5 mm, purple; lateral stamens reduced to petal-like, base white to light purple, tip and margin dark purple, 1.2-1.5 cm long, about 0.6 cm wide; corolla tube short and cylindrical, pale purple, labellum pouch-shaped, upper part dark purple, lower part pale purple. Capsule nearly spherical or ovoid-spherical, length and width axes about 0.9-1.2 to 0.8-1.1 cm, pericarp light green, opening at the top when mature. Mature seeds brownish, rough textured, with a false seed coat, seed coat more prominent. 2n=12.

The Rehmannia glabra has a rhizomatous rootstock that sprouts into new plants. Its root system is particularly robust, with the rhizomes covered in adventitious roots. On a 10 cm long rhizome, there can be 70-90 adventitious roots, which can grow up to 50-90 cm in length. These roots have lateral branches, with the upper root lateral branches especially well-developed. The volume of the underground rootstock and rhizomes is substantial, comparable to the aboveground part.