Growing Lotuses
The Sunset New Western Garden Book does distinguish between lotuses and water lilies.
Water lilies, listed under the genus Nymphaea, have round leaves with a notch at one side where the leaf stalk is attached. The flowers float on the surface of the water or stand above it. Water lilies sold in nurseries are hybrids. Hardy water lilies come in colors ranging from white through yellow to red. Tropical water lilies come in more colors, including blue and purple, but are more sensitive and prefer (no surprise!) to live in areas where orange trees flourish. They can be grown in colder climates, especially if the roots are stored in damp sand over the winter.
Lotuses, in the genus Nelumbo, have perfectly round leaves that spring up in summer above the water level and large fragrant flowers on separate stalks. Lotus roots should be planted in spring in 12 to 18 inches of fairly rich soil, which is then covered with 8 to 12 inches of water. They often will not bloom the first year, unless the summer is warm early. If the water will freeze in your area, the pond should be covered or filled with more water in winter. Nelumbium luteum is the American lotus, with pale, small flowers. The Indian or Chinese lotus, nelumbium nelumbo, usually has pink flowers although white, rose and double varieties are available.
To make things even more confusing there is a genus called Lotus but it's a completely different plant, a member of the pea family. Let's not even go there.