There’s considerable confusion surrounding the common names of aquatic plants in the three genera Nymphaea, Nuphar and Nelumbo. True enough, they all have fairly circular leaves that float on fresh water at least part of the year and grow with their tuberous roots in the mud of a pond or lake (or in a pot!), but they’re not necessarily even closely related. Neophytes often simply call them water lilies, but serious gardeners need to know the difference.
Water lily or waterlily (both are correct) is the preferred name for plants of the genus Nymphaea of the Nymphaeaceae family.
Water lily flowers have numerous petals: at least eight and usually many more. They can be white, pink, red, blue or pale yellow, but never golden yellow (that color is limited to pond-lilies, that is, plants of the genus Nuphar). The center of the flower is usually packed with abundant yellow stamens.
The flowers either float on the water’s surface or are carried on a short stem above the water. This depends on the species. Note too that with water lilies, the seed capsules sink below the water surface, out of sight, when the flower finishes blooming.
The more or less circular leaves have a slit on one side that allows rain water to drain off, and the leaf stalk is attached at the base of the slit. This feature is shared with pond-lilies (Nuphar spp.).
Water lilies are extremely ornamental plants and very popular in water gardens. There are hundreds of hybrids, both tropical and hardy. Some are day bloomers, others are night bloomers.
Water lily is also the name used with a few other plants in the Nymphaeaceae family with similar growth habits, such as the giant water lily (Victoria spp.).
No one seems to agree on what to call plants in the genus Nuphar. They go by such names as water lily (which should automatically be banned to avoid confusion with the genus Nymphaea just described), bonnet lily and spatterdock among others. I recommend pond-lily, largely because it is widely understood on both sides of the Atlantic and has been used for centuries.
Like the water lily, the pond lily a member of the Nymphaeceae family and indeed, the leaves of the two are pretty much undistinguishable, with the same circular shape and drainage slit. However, the flowers are very different. They are golden yellow, a color absent from the water lily palette, and are made up not of numerous petals, but of only 4 to 6 sepals forming a cup. (There are petals, but they’re insignificant.) Also, when the jug-shaped fruit forms, it floats on the surface of the water and therefore remains visible.
The pond-lily is generally considered less attractive than the water lily and is rarely grown in water gardens.
In the strictest sense, the term lotus applies only to plants of the genus Nelumbo, consisting of just two species (Nelumbo nucifera and N. lutea) and their hybrids. Curiously, lotuses do not belong to the Nymphaeaceae family, but rather to their own family, the Nelumbonaceae. In fact, they are not even very close relatives of Nymphaeaceae, but are rather more closely related to plane trees (Platanus spp.) and proteas (Proteaceae), both woody terrestrial plants. If the two families appear similar, it’s because of convergent evolution, both having adopted similar strategies to survive in an aquatic environment.
The lotus leaf is peltate, with the leaf stalk attached to the center, underneath the leaf, rather than the edge. There is no slot to allow rain to drain away. Instead, the leaf is hydrophobic and raindrops bead up on its surface and roll around, eventually being pushed off the leaf by the wind. Only the first leaves of the season float. As the summer advances, the others begin to appear on straight, upright stems sometimes rising more than 5 feet (150 cm) in height above the water.
Lotus flowers are often huge—up to 12 inches (30 cm) in diameter—and are borne above the water on strong stems. Composed of a variable but usually fairly large number of tepals (petals and sepals), they do look superficially like a water lily flower, but can be instantly distinguished by the large cone-shaped floral receptacle in the center of the flower.
When the tepals drop off (they only last a day), the receptacle remains upright, at first green, then brown. It eventually opens to release large hard round seeds. Dried, the receptacle often serves as a floral decoration. When you see these cone-shaped seed capsules with their numerous holes, you know you’re definitely dealing with a lotus.
By now, it should be clear that the lotus (Nelumbo) and the water lily (Nymphaea) are two vastly different, unrelated plants, but … two species of Nymphaea have long been called lotuses, the Egyptian white lotus (Nymphaea lotus) and the blue lotus or blue Egyptian lotus (N. caerulea). Ideally, we should call them, respectively, the Egyptian white water lily and the Egyptian blue water lily … but old names tend to cling to plants for a long time and I don’t think that is going to happen any time soon!
As a result, I find I have to call the two Nelumbo species sacred lotus (Nelumbo nucifera) and American lotus (N. lutea) if I want to make myself perfectly clear. Annoying, isn’t it?
The Botanical Name Lotus
To further confuse the situation, Linnaeus (1707–1778) gave the botanical name Lotus to a genus in the Fabaceae family (legumes) consisting of about 100 terrestrial plants with pea flower-shaped blooms. Simply call them trefoils and remember they have no connection whatsoever with Nymphaea, Nuphar or Nelumbo and therefore, there should be no risk of confusion.
The Right Name on the Right Plant
As gardeners, we should always know the right names for our plants, otherwise the gardening world will become be nothing but a huge tower of Babel!