Herbs, wetland. Rhizomes vertical. Leaves appearing before flowers, several, emergent or sometimes floating, clustered; petiole longer than blade; blade abaxially paler green, adaxially dark bluish green with distinctive velvety sheen, simple, not peltate, oblong-elliptic, base acute to obtuse or sometimes oblique, apex rounded-apiculate or short-acuminate; venation parallel to midvein except near base. Inflorescences: peduncle reclining in fruit, usually equal to or longer than leaves, apex swollen; spathe absent; spadix long-conic. Flowers mostly bisexual, the distal staminate; perianth present. Fruits partially embedded in spadix, green to blue-green. Seed 1, embedded in mucilage. x = 13. The leaf sheathing the peduncle, which has been interpreted as the spathe in Orontium, is a sympodial leaf and is not equivalent to the spathe of other Araceae (T. S. Ray 1988). Orontium also differs in several other characteristics from the presumably related genera Lysichiton and Symplocarpus and has been segregated as a monogeneric tribe (M. H. Grayum 1990).
Fls perfect, bright yellow, covering the linear spadix; spathe consisting of a tubular lf surrounding the base of the scape; stamens 4 or 6; filaments wide and thin; pollen-sacs divergent; ovary partly embedded, unilocular, with 1 ovule; fr a green or brown utricle; stoutly rhizomatous; lvs basal, the stout petiole broadly dilated at base, the blade floating or submerged, with wide midvein. Monotypic.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.