There are two main types of water lilies: hardy and tropical. While the former is naturally more capable of surviving colder temperatures, wintering lilies of both types requires some TLC. Because these plants can have trouble making it through the winter, many gardeners choose to grow their lilies as annual plants, composting them at the end of the season.
If you have enough space and the wherewithal, it is possible to overwinter both hardy and tropical water lilies—but expect to see varying degrees of success since it is a finicky process with multiple factors that may go wrong. Outdoors, the weather can surprise you by becoming colder than expected or with wide temperature swings. You can control conditions better indoors, but sometimes the plants simply aren’t able to adjust.
Winter Care of Tropical Water Lilies
Tropical water lilies are the most difficult to overwinter. Although tropical water lilies do go dormant in the winter, they are only hardy to about USDA Hardiness Zone 9. They will freeze and die if left in a cold pond over winter. It’s very common to grow tropical water lilies as annuals. If you want to try overwintering your tropical water lilies, here are some methods to help you succeed:
- Bring the pot indoors: Store your tropical water lily in a greenhouse, a heated aquarium, or in a heated room under grow lights. Lift the pots in late September or early October (you can also move your water lilies to smaller pots for the winter if needed). Lift the plant to trim back some of its leaves and roots. Replant in a one-gallon container. Place the pot in a small tub of water, keeping the temperature at about 68 degrees Fahrenheit. The idea is to keep your water lily alive, but not actively growing—so don’t fertilize the plant or worry about providing it extra space.
- Remove your lily from its pot: You can also store the plant outside of the pot if it's kept damp. Lift the entire plant, cut off most of the top, and store the rhizome in a plastic bag with some damp peat moss or sand. Keep the bag somewhere dark with temperatures between 50 to 60 degrees Fahrenheit. Check back periodically to make sure it’s not getting dry, soft, or moldy.
- Save tubers for spring: If your plant has tiny tubers growing at the base, you can remove these offsets and store them in water or damp peat moss (also between 50 to 60 degrees Fahrenheit). They should start to sprout in the spring and can then be potted up.
Wait until your pond's water warms in the spring before transporting your water lily back outdoors. The water temperature should be around 70 degrees Fahrenheit for tropical water lilies. If it’s too cool, the plant will revert back to dormancy or could even be killed off by frost.
Winter Care of Hardy Water Lilies
Hardy water lilies are truly hardy to about USDA Zone 4, but potted water lilies will still need some protection. You don’t want to leave them in your water garden if it freezes solid, or even if it tends to freeze and thaw repeatedly. Here are some ways to keep your hardy water lily alive through the winter:
- Move the water lily: Hardy water lilies go dormant for the winter. The foliage will die back or become sparse. When this happens, move the water lily—pot and all—to the deepest part of your pond where the water doesn’t freeze solid. Hardy water lilies actually enjoy a cold, dormant period; leave it there for the winter, then fish it back up when the water warms in the spring. It should resume growing around April. If you don’t have a deep enough pond to keep the plant below the freezing level, it's best to use another method for wintering lilies.
- Bury the plant with mulch: Take the water lily out of the pot and bury it completely in the ground. Mark the spot, cover it with mulch for the winter, then dig and repot the plant in the spring. (We’ve never tried this, and suspect it depends on the type of winter you have. A good snow cover should keep it fine, but a dry, cold winter might kill the plant.)
- Insulate the pond: If your lily is in a small pond, you can insulate the whole pond by covering it with boards and adding a layer of straw, old blankets, or rugs. Be sure to remove the coverings as early in the spring as possible to avoid heating the water, which can cause premature sprouting. While this method requires more hands-on work for your water lilies in winter, it also helps in the spring by saving time scooping leaves and debris from your pond.
- Store it inside: Transport your water lily indoors for the winter and store it in a cool basement or heated garage, keeping the temperature at about 50 degrees Fahrenheit. Bring in the whole pot and place it in a plastic bag or box. Check it periodically to make sure the soil remains moist. Another option is to remove the plant from the pot, then store the tuber in moist peat moss or leaves. (Don’t expect your potted water lily to make a good houseplant. It still needs to go somewhat dormant, and it won’t be particularly attractive indoors.)
Wintering water lilies requires some experience to have success from season to season. Since these plants can be expensive, many gardeners find the process worth trying. Remember to check on your water lilies at least every few weeks in winter. Similar to any other bulbs stored indoors, it doesn’t take long for lilies to dry out or rot if conditions aren’t ideal. Most importantly, remember to pot them up and bring them back outdoors gradually in the spring to enjoy these hard-earned blooms once again.