Fl. Amer. Sept. 2: 370. 1814 (as sagittaefolia).
Rhizomes 2-2.5 cm diam. Leaves floating or submersed; petiole terete. Leaf blade abaxially and adaxially green, linear to lanceolate, 15-30(-50) × 5-10(-11.5) cm, 3-5 times as long as wide, sinus less than 1/3 length of midrib, lobes usually divergent and forming V-shaped angle; surfaces glabrous. Flowers 2-3 cm diam.; sepals 6, abaxially green to adaxially yellow toward base; petals oblong, thick; anthers 3-5 mm, barely or not at all longer than filaments. Fruit green, ovoid, 3-3.5 × 2-3 cm, smooth basally, strongly ribbed toward apex, slightly constricted below stigmatic disk; stigmatic disk green, 14-18 mm diam., nearly entire; stigmatic rays 10-14, linear, mostly terminating 1-2 mm from margin of disk. Seeds 4-5 mm.
Phenology: Flowering mid spring–early fall.
Habitat: Freshwater streams, rivers, ponds, and lakes of coastal plain, extending to freshwater tidal areas
Elevation: 0-50 m
N.C., S.C., Va.
Of conservation concern.
Nuphar sagittifolia is probably best treated as a subspecies. Plants intermediate between it and N. advena are treated under N. advena. The clinal variation pattern between the two taxa is apparently maintained via selection by vernalization (C. E. DePoe and E. O. Beal 1969; E. O. Beal and R. M. Southall 1977).
This taxon is the Cape Fear spatterdock of the aquarium trade.