Synonymy

Nymphaea alba consocies Pearsall 1918; Nymphaea occidentalis consocies Pearsall 1918; Nymphaeetum albae Tansley 1939; Nymphaeetum occidentalis Tansley 1939; Nymphaeetum minoris Vollmar 1947; Nymphaea alba sociations Spence 1964.

Constant species

Nymphaea alba.

Rare species

Nuphar pumila, Nymphoides peltata.

Physiognomy

Nymphaea alba is a native water-lily, but a plant widely introduced to lakes and ponds because of the ornamental character of its large white flowers, appearing above water in mid-summer and attractively set off against the dark green floating pads which are put up from the stout rhizomes some two months earlier (Heslop-Harrison 1955d). Some authorities (Clapham et al. 1962, but not Tutin et al. 1964) distinguish a ssp. occidentalis, to include altogether smaller plants than those reserved for a ssp. alba, but there is continuous variation between the extremes of size, and the taxa have only rarely been separately recorded in the available data. For these reasons, it is difficult to give a precise indication of the natural floristic affinities of the plant or to know how taxonomic differences within it are reflected among the associates. But there seem to be three kinds of floatingleaved vegetation dominated by water-lilies in which N. alba plays a prominent role. Quite commonly, and particularly in the English lowlands, it occurs in abundance among Nuphar lutea, and in this scheme such stands are included within the Nuphar community. In many situations, though, N. lutea is extremely rare among abundant N. alba and it is such vegetation that forms the basis of the Nymphaeetum albae, of which two types have been distinguished. Few other plants occur with any frequency throughout the community, indeed many stands are very species-poor, but Potamogeton natans varies from occasional to very common, and there is quite often some submerged P. obtusifolius. Lemna minor can also be found, although extensive covers of this are best seen as representing mosaics of the Lemnetum minoris among the water-lily vegetation.

Sub-communities

Species-poor sub-community. Very often, N. alba is the only plant in this vegetation, with just occasional P. natans or P. obtusifolius, but the rare Nuphar pumila has been recorded here in some of its Scottish localities and, in lowland England, Nymphoides peltata, another rarity that may have been introduced to parts of its present range (Perring & Walters 1962, Perring 1968).