White water lilies are common in ponds in our area; the pink form is rarer, but not very rare. The pink form is listed as forma rosea in some references, but Gray points out that the white form passes by degrees into the pink form, as we can see in these pictures. The pink form was fairly common in this pond in the Homewood Cemetery, where these plants were blooming in early June. It is possible that these plants are descended from a cultivated variety, but they are certainly naturalized now.
Gray places this species in the genus Castalia, reserving Nymphaea for the yellow-flowered water lilies:
CASTALIA Salisb. WATER NYMPH. WATER LILY. Sepals 4, green outside, nearly free. Petals numerous, in many rows, the innermost gradually passing into stamens, imbricately inserted all over the ovary. Stamens indefinite, inserted on the ovary, the outer with dilated fila ments. Ovary 12-35-celled, the concave summit tipped with a globular projection at the center, around which are the radiate stigmas; these project at the margin, and are extended into linear and incurved sterile appendages. Fruit depressed-globular, covered with the bases of the decayed petals, maturing under water. Seeds enveloped by a sac-like aril. — Flowers white, pink, yellow, or blue, very showy. (Kastalia, a mythical fountain on Parnassus, sacred to Apollo and the Muses.) NYMPHAEA L. in part.
C. odoràta (Ait.) Woodville & Wood. (SWEET-SCENTED WATER LILY.) Rootstock with few and persistent branches; leaves orbicular (0.5-2.2 dm. wide), deeply-cordate-cleft at the base, the margin entire, often crimson beneath; stipules broadly triangular or almost kidney-shaped, notched at the apex, appressed to the rootstock; flower white, very sweet-scented (0.5-1.3 dm. in diameter, when fully expanded, opening early in the morning, closing in the afternoon); petals obtuse; anthers blunt; aril much longer than the distinctly stipitate ellipsoid seeds, these about 3 mm. long. (Nymphaea odorata Ait., including var. minor Sims.) — Ponds and still or slow-flowing water; common. June-Sept. Passing to the somewhat ill-defined forma ròsea (Fursh) Britton, with pink or bright pink-red flowers. — Shallow ponds, mostly near the coast. Var. gigantea (Tricker) Fernald. Larger; leaves 2-4 dm. broad, the margins turned up; flowers (white or nearly so) 1-1.5 dm. in diameter, less fragrant; sepals greenish. (Nymphaea odorata, var. Tricker.) — Del. to Fla. and La. (Mex., W. L, S. A.)