Water lilies (Nymphaea spp.) are excellent plants in many settings, all of them involving ponds or other large outdoor water features. They are also wonderfully beautiful plants, which leads many people to wonder whether they can grow them indoors to enjoy them on a daily basis. While it is possible to grow water lilies as houseplants, it's very difficult.
About Water Lilies
Water lilies belong to the genus Nymphaea. They are distributed throughout most of the world but native to South Africa, the northern hemisphere, and Australia. Although there are marked differences in the various species, water lilies are all prized for their great beauty. They typically grow with large floating leaves and delicate, often colorful flowers.
In general, the basic requirement for growing successful water lilies outdoors is to provide the proper water temperature and ambient temperature. No water lilies grow in areas where water freezes to the bottom of the pond or container, though through careful steps keeping water lilies alive through the winter is possible.
There are about 50 species of water lilies with even more varieties within those species. Although there are several ways to classify water lilies, including by their growth habit, they are most commonly divided into two groups: tropical and hardy water lilies.
Tropical Water Lilies
Tropical water lilies are strictly warm-water plants. They cannot tolerate water temperatures below 60 degrees Fahrenheit, and most will fail to thrive in water temperatures below 70 degrees Fahrenheit.
These water lilies tend to have large and colorful flowers that are held on stalks above the water. There are both day- and night-blooming varieties. Flowers on tropical species are typically open for three to four days at a time, and the individual plants spread between 3 and 12 feet. These are some of the world's most prized water lilies.
Hardy Water Lilies
Hardy water lilies grow in temperate regions, including throughout North America. They tend to have smaller foliage than tropical water lilies, and their flowers float on top of the water.
There is no strict water temperature requirement for hardy water lilies other than that the water cannot freeze solid. Hardy water lilies don't boast the same extravagant blossom colors as tropical water lilies. And in many species, the flowers gradually change colors over the few days they are open.
Growing Water Lilies Indoors
It would be wonderful to have a bowl of water lilies somewhere at home with a single flower or cluster of flowers rising above the water. Unfortunately, this is much easier said than done.
Most water lilies, especially the tropical species, require a fairly large growing area. Although estimates vary depending on the species, it's a safe bet that each plant needs about 36 square feet of water surface area to thrive. In practical terms, this means a 6 foot-by-6 foot body of water (such as a small pond). This usually is not an option inside most residences.
However, if you're not planning to keep the plants thriving for years, it is possible to grow hardy water lilies in containers as small as 15 gallons. But to do so indoors requires a few extraordinary measures.
First, the plants will need as much sun as you can provide—and potentially a supplemental grow light—to bloom. And while they are fully aquatic, they will still need a growing medium. The best option is to fill a plastic pot with rocks at the bottom to weigh it down and then add a growing medium, such as sand, perlite, or aquatic planting mix. Sink the pot inside the container of water where you plan to grow your plants, and then put the rhizome of the plant into the medium. Also, add a liquid fertilizer for aquatic plants to the water. Finally, make sure the water is the proper temperature depending on the water lily species, and maintain the water level by adding more water as it evaporates.
One of the major drawbacks to growing water lilies indoors is the smell of stagnant water, though murky water shouldn't damage the plants. It's OK to change the water every so often; if you do, be sure to add more liquid fertilizer to the fresh water. Also, indoor water lilies are vulnerable to pests, including aphids, mealy bugs, scale, and whiteflies. Ultimately, even if you provide the best growing conditions you can, you still might not get a bloom. So if you do choose to go this route, be prepared that it might not work every time.
Nash, Helen. Complete Guide to Water Garden Plants. Sterling, 2003