Water lilies are excellent plants in many settings, all of them involving ponds or large outdoor containers. But they are also wonderfully beautiful plants and the question comes up sometimes: "Can I grow water lilies indoors?" In a word (or four): possibly but not easily.
About Water Lillies
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 prized for their great beauty. They typically grow with large floating leaves and delicate, lovely 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 (although through careful steps, keeping waterlilies alive through the winter is possible). Beyond that, there is great variation among the different species.
Altogether, there are about 50 recognized species of water lilies with untold hybrids. 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
The tropical water lilies are strictly warm-water plants. They cannot tolerate water temperatures below 60 F and most will fail to thrive in water temperatures below 70 F. Tropical water lilies tend to have larger and more 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 three and 12 feet. Under the right conditions, 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, and their flowers float on top of the water. There is no real 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 in the house with a single flower or cluster of flowers rising above the water. Unfortunately, this will be much easier said than done. Most water lilies, and 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 over the long-term. In practical terms, this means a six-foot by six-foot body of water (like a small pond). This is not a practical option for the typical residential home.
So is there anything you can do?
There is. If you're not planning on keeping the plants thriving for years, it is possible to grow hardy water lilies successfully in containers as small as 15 gallons. To do so well indoors, however, requires a few extraordinary measures.
First, the plants will need as much sun as you can provide, and failing that will probably require a grow light to bloom. And while they are fully aquatic, they will still need a growing medium; the best option is to submerge the growing container in the water and weight it down with rocks. Once the container is submerged, fill the container with water, so the leaves float naturally on the surface and use a small dose of aquatic plant fertilizer to help them along.
Finally, make sure the water is the proper temperature depending on the species and the water level is maintained. One of the major drawbacks to growing water lilies indoors is the smell of stagnant water, so it's okay to change the water every so often, providing you're careful to add more fertilizer. In the wild, they often grow in stagnant water, so don't worry that your plant will be damaged by murky water. Indoor water lilies are vulnerable to pests including aphids, mealy bugs, scale, and whitefly.