Water lilies are rooted in the soil underneath slow moving bodies of fresh water and their leaves and flowers float on the water’s surface. Hardy water lilies live in temperate climates and bloom only during the day but tropical water lilies, the only group to contain blue-flowered plants, live in tropical environments and can bloom either during the day or at night.
There are about 70 species of water lilies throughout the world and their beauty has led to their widespread use as ornamental plants. For example, the Mexican water lily, native to the Gulf Coast of North America, is now planted throughout the North American continent. They are highly adaptable but should you wish to curtail their spread you need only to cut off the top growth.