The warmth of spring beckons the leaves of water lilies to the calm surfaces of ponds, lakes, and slow-moving streams. The young leaves emerge in the glow of sunlight and then unfurl to become lily pads. Afloat, the cool water on their backs and the sunlight drenching their faces, lily pads, for a few short months each year, enjoy a life akin to the type of summer vacation we dream of.

Lily pads bring color and life to their quiet freshwater homes. They are at their most beautiful when they bloom at the water's surface, producing flowers that range in color from white to pink, yellow, red, or (in some tropical species) even blue or purple. They also serve as a vital habitat feature for a variety of animals, with their best known occupants being frogs.

Lily pads provide an important hiding place for frogs, which are susceptible to underwater predators such as fish and water snakes. On the safety of the lily pad, a frog can relax or catch flies without fear of predation. Other species that are often found relaxing on lily pads include painted turtles, damselflies, dragonflies, and beetles, the latter of which serve as the primary pollinators for a number of different species of water lily. The undersides of the pads are also home to a variety of small creatures, including snails. The females of long-horned beetles and whirligig beetles attach their eggs to the undersides of lily pads.

As the heat of summer settles in, the shade provided by lily pads becomes increasingly important for keeping fish and other underwater species cool. The shade also limits the growth of algae, which might otherwise bloom excessively, leading to decreased dissolved oxygen levels in the water and die-offs in fish and other species.

Water lilies, however, have their own dark side. Indeed, when a non-native water lily is introduced into a body of freshwater, it may grow excessively, overcrowding and choking out animals and other plants. One such example is the fragrant water lily (Nymphaea odorata), which is native to eastern North America. However, because of its popularity as an ornamental, the species is now found throughout North America and other parts of the world. It is especially problematic in western Washington, where it has been introduced into lakes and has grown to such great density that it has caused water in some lakes to stagnate, triggering declines in dissolved oxygen and affecting the survival of fish and other species.

Of course, in their native habitats, water lilies make for wonderful scenery. But while water lilies are perennial, a single plant surviving for several years rooted in the mud, in keeping with the seasons, the life of the lily pad itself is fleeting. By late summer, the majority of lily pads have begun to decay, their vivid green fading to yellow and brown, their parts detaching and disappearing into the water. The water lily falls dormant. It will not be awakened again until next spring, when a new generation of lily pads will emerge.
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Kara Rogers is the senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is also a member of the National Association of Science Writers and a contributor to the Britannica Blog, where she runs a series called Science Up Front. She holds a Ph.D. in Pharmacology/Toxicology, but enjoys reading and writing about all things science. You can follow her on Twitter at @karaerogers.

This post also appears on the Britannica Blog.