Nature Notes: Water Lilies
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By Ed Robinson
Lately I have been enjoying the appearance of water lilies in several large ponds along our local highways. It is easy to see why the French impressionist Claude Monet was inspired to create his famous series of “Water Lilies” canvases, with over 250 paintings of his water garden in the last 30 years of his life. But this plant is not just another pretty face.
Water lilies are a family of freshwater flowering plants called Nymphaeaceae. They can be found around the world, with roughly 70 species identified by scientists so far. Technically they are perennial aquatic herbs, found in temperate and tropical climates in northern and southern hemispheres. While the large leaves and flowers float on the surface of ponds and lakes, they are attached by long stems (six to seven feet in length) to roots firmly established in the soil below. The roots are classed as rhizomes, fleshy tubers that store nutrients for future growth and expansion. This allows the plants to survive harsh winters, while the surface vegetation dies and falls to the bottom. Pollination is accomplished by beetles, flies, bees or by wind. The plants produce seeds that allow the plant to spread.
Because of their beauty, water lilies have been transplanted all over the world, and hybridized to create new varieties. They may blossom over a period of several months, as late as September in our area, in colors ranging from pink to red, white to yellow. The flowers open during the day, close in the evening, and may last several days before new blossoms develop. As with many other ornamental plants, water lilies can become invasive and they can cause serious problems in stagnant or slow moving bodies of water. Due to a deep and wide-spread root system, it can be difficult to control or eradicate this plant without the use of chemical herbicides applied by a licensed professional. A friend of mine has an ornamental water garden at his home in NY, and every few years he has to drain the water and wade in with loppers and shovel to dig out the overgrown lily root systems.
The leaves, or pads, provide shade and shelter for fish and other aquatic creatures. Dragonflies and frogs are regular users of the pads for resting spots. The lily has evolved to allow the exchange of carbon dioxide and oxygen through pores on the surface of its leaves, called stomata. In hot summer weather, the leaves can help keep the waters below from excessive warming. With excessive growth, water lilies can substantially lower the oxygen levels in the water. By spreading over the surface of a pond or marshy area, water lilies gain the advantage of sunlight for photosynthesis but they can crowd out other plant species. When the leaves and stems die off in the autumn, they add more decaying plant matter to the bottom, lowering oxygen levels, and sediment may be prevented from flowing downstream in rivers.
I used to do a lot of largemouth bass and northern pike fishing in a large bay off Lake Ontario, and the quiet lily pads in the backwaters provided a lot of good sport, as long as I could avoid hooking the tough leaves and stems. Animals such as muskrats, beavers and deer will eat the stems and leaves of water lilies, and ducks have been observed eating the seeds. Studies have shown that water lilies serve a valuable role in sequestering heavy metals like cadmium, mercury and nickel in polluted waters, particularly if the vegetation is then removed for controlled disposal. Some scientists have experimented with harvesting water lilies to make briquettes that can be burned for fuel, but the economics of this have yet to be proven.