The two main species of waterlilies in the Okavango are the day-lilies, Nymphaea nouchali caerulea, and the night-lilies, Nymphaea lotus, which are sometimes called lotus lilies. The day-lilies are more common, and the species are fairly easy to tell apart.
As you might expect, day-lilies open in mid/early morning, and close in the afternoon. Their large floating leaves have smooth edges; their flowers start off as a delicate shade of violet-purple (earning them the name of ‘blue lily’) with only the centre having a yellowish tinge. These last for about five days, gradually turning whiter as they age, before the stem twists and drags the pollinated seed-head under water. There it matures until the seeds are eventually released, complete with air-filled bladders to help them float and disperse better.
Night-lilies are similar but have much darker green leaves, sharply serrated at the edge. The flowers have creamy white petals, edged with yellow, and a strongly yellow centre; these flowers often lie very flat on the surface, facing directly upwards. They open in the late afternoon and close in the early morning, relying for their pollination on night-flying insects.