Plants (30-)50-150(-200) cm. Stems erect, glabrous or densely and retrorsely pubescent. Leaves: ocrea reddish brown, funnelform, 1-2.2 cm, margins oblique, glabrous or pilose; petiole 0.8-3.5(-4) mm; blade narrowly lanceolate to ovate, 5-20 × 2-8 cm, not subcoriaceous, base truncate or obtuse to subcordate, margins sometimes irregularly undulate, ciliate or, rarely, glabrous, apex acuminate, faces not glaucous, glabrous or pubescent. Inflorescences terminal, sometimes also axillary, paniclelike; peduncle 0-4 cm, glabrous or pubescent. Pedicels 0.5-0.1 mm. Flowers 2-4 per ocreate fascicle, all flowers with stamens well developed; perianth white or greenish white, 2-4 mm; tepals dimorphic, rarely slightly so, ovate, apex obtuse; anthers yellow to pink. Achenes included or exserted, tan to grayish brown, not beaked distally, 2.6-3.8 × 2-3 mm, shiny, faces usually not concave. 2n = 20.

Aconogonon alaskanum has been considered conspecific with the morphologically similar Eurasian A. alpinum (Allioni) Schur, but the taxa differ in leaf size and achene characters. Nomenclatural issues were clarified by J. T. Kartesz and K. N. Gandhi (1990) and K. L. Chambers (1992).