Rhizomes branched or unbranched, erect or repent; elongate stolons present or absent. Leaves mostly floating (vernal leaves submersed; blades sessile, broad). Leaf blade orbiculate to widely ovate or elliptic, basal lobes divergent to overlapping, margins entire to spinose-dentate, apex of lobe acute or acuminate to widely rounded; primary venation mostly palmate, midrib with 1 vein. Flowers floating or emersed, opening diurnally or nocturnally; perianth perigynous, spreading at anthesis; sepals 4, mostly greenish, ovate to elliptic; petals 8-many, spirally arranged or wholly or partially whorled, showy, white, pink, blue, or yellow, broadly lanceolate or ovate to obovate, grading into stamens; stamens yellow or cream-colored, inserted on lateral surface of ovary, spreading at anthesis, sometimes with distal connective appendage; ovary shorter than petals and stamens; stigmatic disk with prominent, distinct, upwardly incurved appendages around margin. Fruits borne on curved or coiled peduncles. Seeds nearly globose to ellipsoid, to 5 mm; aril present. x = 14.
Species 35-40 (9 in the flora).
Nymphaea is an important genus of ornamental plants, with numerous cultivars or wild forms grown in water gardens. Some have become naturalized in some places, particularly in Florida, and two such taxa are included in this treatment. A third, N. ×daubenyana W. T. Baxter ex Daubeny (N. micrantha Guillemin & Perrottet × N. caerulea Savigny), with blue flowers and entire leaves and with a proliferous mound of fibrous tissue above insertion of petiole, may also be encountered in Florida.
Prior to conservation in its current sense, the name Nymphaea was frequently used for the genus now known as Nuphar.
|1||Sepals abaxially flecked with short dark lines.||> 2|
|1||Sepals abaxially uniformly greenish, reddish, or yellowish.||> 3|
|2||Leaf blade with dentate to spinose-dentate margins; petals white; connective appendage projecting to 3 mm or more beyond anther.||Nymphaea ampla|
|2||Leaf blade with entire to sinuate margins; petals pale violet to nearly white; connective appendage mostly projecting 1 mm or less beyond anther.||Nymphaea elegans|
|3||Petals blue, lavender, or purple; connective appendage projecting to 4 mm or more beyond anther.||Nymphaea capensis|
|3||Petals white to pink, cream-colored, or yellow; connective appendage projecting less than 2 mm beyond anther.||> 4|
|4||Leaf blade with spinose-dentate margins, abaxially slightly to densely puberulent.||Nymphaea lotus|
|4||Leaf blade with entire or sinuate margins, abaxially glabrous.||> 5|
|5||Appendages at margin of stigmatic disk slightly club-shaped; flowers opening nocturnally; leaf blade with central web of cross veins between major veins.||Nymphaea jamesoniana|
|5||Appendages at margin of stigmatic disk tapered or boat-shaped; flowers opening diurnally; leaf blade with radiate venation, without central weblike pattern.||> 6|
|6||Petals yellow; plants bearing stolons.||Nymphaea mexicana|
|6||Petals white; plants not bearing stolons.||> 7|
|7||Petals 17–43; filament widest below middle; rhizomes repent.||Nymphaea odorata|
|7||Petals 8–17; filament widest above middle; rhizomes erect.||> 8|
|8||Appendages at margin of stigmatic disk 0.6–1.5 mm; lines of insertion of sepals on receptacle not prominent.||Nymphaea leibergii|
|8||Appendages at margin of stigmatic disk mostly 3 mm or more; lines of insertion of sepals very prominent, forming tetragon on receptacle.||Nymphaea tetragona|