4. Nuphar advena (Aiton) W. T. Aiton, Hortus Kew. 3: 295. 1811.
Nymphaea advena Aiton, Hort. Kew. 2: 226. 1789; Nuphar fluviatilis (R. M. Harper) Standley; N. lutea subsp. advena (Aiton) Kartesz & Gandhi; N. lutea subsp. macrophylla (Small) E. O. Beal; N. lutea subsp. ozarkana (G. S. Miller & Standley) E. O. Beal; N. ozarkana (G. S. Miller & Standley) Standley; N. puteora Fernald; N. ×interfluitans Fernald; Nymphaea advena subsp. macrophylla (Small) G. S. Miller & Standley; N. chartacea G. S. Miller & Standley; N. fluviatilis R. M. Harper; N. ludoviciana G. S. Miller & Standley; N. macrophylla Small; N. microcarpa G. S. Miller & Standley; N. ovata G. S. Miller & Standley; N. ozarkana G. S. Miller & Standley; N. puberula G. S. Miller & Standley
Rhizomes mostly 5-10 cm diam. Leaves mostly emersed, occasionally floating or submersed; petiole terete or adaxially slightly flattened. Leaf blade abaxially and adaxially green, broadly ovate to nearly orbiculate, 12-40 - 7-30 cm, 1-2 times as long as wide, sinus 1/3-1/2 length of midrib, lobes overlapping to divergent, often forming angle of 90° or greater; surfaces abaxially glabrous to sparsely pubescent. Flowers to 4 cm diam.; sepals mostly 6, abaxially green to adaxially yellow, rarely red-tinged toward base; petals oblong, thick; anthers 3-7 mm, longer than filaments. Fruit green, ovoid, 2-5 × 2-5 cm, moderately ribbed, slightly constricted below stigmatic disk; stigmatic disk green, occasionally reddened, 13-25 mm diam., entire to crenate; stigmatic rays 9-23, linear to lanceolate, terminating 1-3 mm from margin of disk. Seeds 3-6 mm.
Flowering mid spring-early fall, extended farther south. Ponds, lakes, sluggish streams and rivers, springs, marshes, ditches, canals, sloughs, and tidal waters; 0-450 m; Ont.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Maine, Md., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.; Mexico (Coahuila, Tamaulipas); West Indies (Cuba).
Nuphar advena is extremely variable and intergrades with N . orbiculata , N . ulvacea , and N . sagittifolia in areas of sympatry. Intergradation with N . variegata (E. O. Beal 1956) can be observed in the mid-Atlantic region, although most floristic treatments from the area of overlap treat the two taxa as distinct species. Local variation in the Ozark Mountains and in Texas, the basis for the names Nymphaea ozarkana , N . ovata , and N . puberula , is not considered sufficient to warrant recognition.
Schneider, E. L. and L. A. Moore. 1977. Morphological studies of the Nymphaeaceae. VII. The floral biology of Nuphar lutea subsp. macrophylla. Brittonia 29: 88-99. Wiersema, J. H. and C. B. Hellquist. 1994. Nomenclatural notes in Nymphaeaceae for the North American flora. Rhodora 96: 170-178.