Water lilies are best known as pond ornaments, but their floating leaves and buried roots also change the water around them. For a pond owner, their biggest value is practical: shade, calmer conditions for fish, and fewer algae problems. The same leaves that help in part of a pond can harm it when they cover the whole surface. Outside the garden, people have eaten them, painted them, and tested them for cleaning polluted water.
How Water Lilies Shade and Cool a Pond and Limit Algae
Lily pads shade the water directly beneath their leaves.1Scott Aerator. Lily Pads in Ponds: Benefits, Drawbacks & Control On hot days, the shallow areas under the pads stay cooler.2ILM Environments. Are Lilies Taking Over Your Lake or Pond? Less light reaches the water, so some algae and submerged weeds grow less.3Scott Aerator. Lily Pads in Ponds: Benefits, Drawbacks & Control
They also compete with algae for food. Lilies take up nutrients from the water that algae would otherwise use,4Saiwc. What Are the Benefits of Planting Waterlilies in Ponds? and they absorb high amounts of phosphorus, a nutrient that commonly drives algae blooms.5ILM Environments. Are Lilies Taking Over Your Lake or Pond?
Many pond keepers aim for lilies over roughly half to two-thirds of the surface. Some open water lets sunlight and air reach the rest of the pond. Too little cover gives little shade and little algae control, and too much tips into the problems of dense mats described below.
Matching the plant to the pond is how you keep cover in balance. Hardy lilies spread and cover a lot of surface, while many tropical and smaller hardy cultivars stay compact. Most lilies need several hours of direct sun to flower well, so a spot shaded all day by trees gives you leaves but few blooms. They prefer still or gently moving water and sulk in the spray or current of a fountain or waterfall. Planting depth matters too: shallow for small types, deeper for vigorous ones, so leaves can reach the surface without strain.
Algae can still get through. Lilies shade only the water they cover, so a sunny open stretch can turn green while the water under the pads stays clear. Algae also feeds on nutrients entering from outside, such as lawn runoff, fish waste, and decaying leaves, which lilies can only partly absorb. A heavily stocked fish pond may still need a filter or aeration.
Habitat for Fish, Frogs and Insects
Young fish shelter beneath lily pads among the long stems, which form something like an underwater forest.6Forest Society. Something Wild: Water Lilies: Sunken Forest & A Summer Oasis Larger fish such as bass and pickerel wait at the edges of lily beds to hunt fish, frogs, and insects.7Forest Society. Something Wild: Water Lilies: Sunken Forest & A Summer Oasis A lily patch sets up a small food web of its own, and it also offers breeding grounds for amphibians and small water animals as well as fish.8Eco Green Services. The Enchanting World of Water Lilies: Nature’s Floating Jewels
In a koi or goldfish pond, pads give ornamental fish shade and a place to retreat, and the cover makes them harder for herons and other predators to spot. Shaded, cooler water lowers stress on fish during summer heat. Koi may nibble or uproot young lilies, so keep plants in pots with gravel on top or shield them with a cage until they are established.
Frogs often rest on the pads, using them as a safe perch near the water. Dragonflies and damselflies land on leaves and stems, and their young develop underwater among the plants. Small insects and snails live on the plants and become food for fish and visiting birds.
Below the surface, lilies anchor into the bottom from a rhizome, the thick buried stem the plant grows from. That helps reduce erosion and keeps mud from clouding the water again.9ILM Environments. Are Lilies Taking Over Your Lake or Pond? The plant also pumps air down its stems to the buried stem so it can live in airless mud.10PubMed. Internal winds in water lilies: an adaptation for life in anaerobic sediments
When Water Lilies Become Too Much
Fragrant water lily is listed as a noxious weed in some regions because it grows in dense patches.11King County Noxious Weed Control Program. Fragrant Water Lily Weed Alert Those patches crowd out native plants and use up oxygen in the water.12King County Noxious Weed Control Program. Fragrant Water Lily Weed Alert Stagnant mats can absorb sunlight and warm the water, the opposite of partial shade.13King County Noxious Weed Control Program. Fragrant Water Lily Weed Alert Still water between the mats can also become a mosquito breeding spot.14King County Noxious Weed Control Program. Fragrant Water Lily Weed Alert
Several signs suggest your lilies have taken over. The surface is almost fully covered, leaving little open water for sunlight and air. Fish gasping at the surface in the early morning suggest low oxygen, which tends to be lowest then. Water that smells stale or sulfurous under the mats points to decay and poor circulation. Other submerged and marginal plants thinning out or vanishing is another clue.
To keep lilies in check, grow them in pots so the rhizomes can’t spread, and divide crowded plants every few years. Thin out leaves and remove dead pads in summer. Don’t plant fragrant water lily in natural lakes where it is listed as a weed.
Some invasive floating plants look like lilies, so check what you have before you buy, plant, or remove it. A local extension office can help if you’re unsure.
Cleaning Up Nutrient-Rich and Polluted Water
In tests, some water lily varieties lowered phosphorus and ammonia in nutrient-heavy water.15PubMed. Differential efficacy of water lily cultivars in phytoremediation of eutrophic water contaminated with phosphorus and nitrogen How much they removed depended on the variety and how well the plants were growing.16PubMed. Differential efficacy of water lily cultivars in phytoremediation of eutrophic water contaminated with phosphorus and nitrogen In one wastewater project, artificial wetlands planted with water lilies and other plants removed more than 90% of ammonia and coliform bacteria.17Bioscientist: Jurnal Ilmiah Biologi. Constructed Wetland-Based Wastewater Management Model for Slum Settlements in 9-10 Ulu Urban Village, Jakabaring District, Palembang City
Water lilies can also survive in water heavy with metals such as cadmium.18edie. Water lilies absorb heavy metal pollution They can absorb metals up to 16% of their dry weight.19Water Online. Water Lilies “Sponge” Heavy Metals Experiments showed a marked drop in cadmium in industrial sludge, with promising results for mercury, nickel, and cobalt.20Water Online. Water Lilies “Sponge” Heavy Metals Tiny glands on the leaves and roots store the metals.21PubMed. Accumulation of heavy metals in epidermal glands of the waterlily (Nymphaeaceae)
At home, your lilies take up some nutrients, but a few potted plants will not treat truly polluted water. Plants that have absorbed metals become contaminated, so they should not be eaten or put in compost that goes on food gardens. Removing spent leaves keeps stored nutrients from returning to the water as they rot.
Eating Water Lilies
People have reviewed fifteen water lily and lotus species as food and nutrition sources.22Applied Food Research. Review on edible water lilies and lotus: Future food, nutrition and their health benefits In Egypt and parts of Africa and Asia, water lily fruits, seeds, and rhizomes are ground into flour.23PubMed Central. Multianalytical investigation reveals psychotropic substances in a ptolemaic Egyptian vase The rhizome of the white Egyptian water lily is about 24% protein,24Food Bioscience. Characterization of water lily (Nymphaea lotus) for nutrients, anti-nutrients, phytochemicals, and antioxidant capacities so it can be a meaningful plant food.
Before harvesting from your own pond, remember that only certain species are traditionally eaten, so a lily growing in your pond is not automatically a food plant. Pond plants can hold whatever pollutants are in their water, so the water source matters. Correct identification matters, since other water plants are not safe to eat. Ornamental garden varieties were bred for flowers, not for eating, and their edibility is not established.
Blue Lotus and Traditional Medicine
The blue water lily, often sold as “blue lotus,” is actually a water lily, not a true lotus.25PubMed Central. The purity of sacred lotus: superhydrophobic self-cleaning plant surfaces and the consequences revisited Ancient Egyptian and Maya art suggests priests used water lilies to bring on trance states.26Journal of Ethnopharmacology. Transcultural use of narcotic water lilies in ancient egyptian and maya drug ritual Residues consistent with the blue water lily were found in an ancient Egyptian vase.27PubMed Central. Multianalytical investigation reveals psychotropic substances in a ptolemaic Egyptian vase The flowers and buried stems contain plant compounds that can act on the brain.28PubMed Central. Multianalytical investigation reveals psychotropic substances in a ptolemaic Egyptian vase Several species have also been used in African traditional medicine as sedatives.29PubMed Central. Multianalytical investigation reveals psychotropic substances in a ptolemaic Egyptian vase
Products sold as blue lotus today appear as teas, tinctures, and extracts, and their contents and strength can vary. Their effects on people have been little studied, so dosing and safety are not well established. Avoid combining them with alcohol or sedatives, and ask a doctor first if you take medicines.
Water Lilies in Art, Design and Science
Water lilies come in almost every petal color from black to white, more than any other flowering plants.30Horticulture Research. Water lilies as emerging models for Darwin’s abominable mystery Monet painted about 250 water lily works from his garden at Giverny,31Art Institute of Chicago. Water Lilies and those paintings helped open the way to abstract art.32Galerie Mont-Blanc. Claude Monet and Impressionism: Focus on the Water Lilies paintings
The giant Amazon water lily’s leaf stays stiff thanks to a branching network of ribs underneath. It gets strength from little material, a lesson engineers study.33PubMed Central. Gigantic floating leaves occupy a large surface area at an economical material cost34Fractal and Fractional. Mechanical Properties and Energy Absorption Characteristics of the Fractal Structure of the Royal Water Lily Leaf Under Quasi-Static Axial Loading The famous self-cleaning, water-repelling leaf, though, belongs to the lotus; water lily leaves get wet.35PubMed Central. The purity of sacred lotus: superhydrophobic self-cleaning plant surfaces and the consequences revisited Water lilies also split off very early from other flowering plants,36PubMed Central. The water lily genome and the early evolution of flowering plants so they help scientists understand how the first flowers developed.37PubMed. Water lily complete genomes illuminate the innovations of water lilies and early angiosperms Their flowers can heat up to attract beetles that pollinate them.38PubMed Central. The Role of Thermogenesis in the Pollination Biology of the Amazon Waterlily Victoria amazonica
Water lilies and lotus are separate plants, though people often use the names interchangeably. Lotus leaves and flowers usually rise on stalks above the water. Water lily leaves and flowers usually float on the surface, which is a quick way to tell them apart in a pond.