Nuphar is a genus of aquatic plants in the family Nymphaeaceae, with a temperate to subarctic Northern Hemisphere distribution.

[3] Nuphar species are aquatic,[4] perennial, rhizomatous, heterophyllous herbs[5] with branching rhizomes,[6][5] which are not stoloniferous.

[7][4] The solitary,[4] subglobose,[8][4] diurnal,[6] pedunculate, floating[4] or emergent flowers[6] have glabrous to pubescent peduncles.

[7] The flowers have 5-9(-12)[6] yellow, green or red, persistent,[7] oblong, obovate, or orbiculate sepals.

[7][5] The 0.5–5 cm wide,[4] ovoid to urceolate fruit,[5] borne on straight peduncles,[6] bears smooth, exarillate,[5] up to 6 mm long seeds.

In 2017, the abundant fossilized seeds of a water lily, known as Notonuphar, were identified in the Eocene-aged La Meseta Formation of Seymour Island, Antarctica.

The seed anatomy of Notonuphar closely resembles that of Nuphar, and for this reason, both are thought to be sister genera.

[50] Like many other vigorously growing members of the Nymphaeaceae, some species of Nuphar tend to cover the water surface completely, blocking out the light and thereby killing both submerged plants and less competitive surface-growing aquatics.

Whether the roots may be eaten, as is widely reported, is open to doubt; some sources claim that they are too bitter, too full of tannin, or simply too poisonous to eat unsoaked, except when treated for so long that they are not viable as a famine food.

They then are pleasant and nutritious, but require a lot of work to harvest and strip from the fruit capsule.

To some extent this may be circumvented rotting the fruit under water for three weeks or more, after which removing the seeds is easier.

[58] The presence of such compounds could explain some of the medicinal uses[53] There has been growing interest in Nuphar alkaloids, their biological and pharmacological significance and their synthesis in recent decades.

[59][60] Apart from pharmaceuticals, the leaves of Nuphar are reported to contain sufficient concentrations of tannin to have been widely used for tanning and dyeing leather, and also as a styptic for staunching bleeding.