Tropical waterlilies are spectacular flowering water garden plants, but they are tender and can’t tolerate cold or frost. If you live in colder climates and don’t grow them in a tropical house, you are faced with two choices. Either treat them as annuals or overwinter them.
Kathy Jentz, editor of the Water Garden Journal for the International Waterlily and Water Gardening Society, recommends the latter. She says: ‘Tropical waterlilies can be expensive and will not survive freezing temperatures, so they should be overwintered as dormant plants.’
What’s the Difference Between Hardy and Tropical Waterlilies?
Hardy waterlilies are pond plants that can survive winter down to US hardiness zone 3, provided the rhizome doesn’t freeze. Tropical waterlilies can’t tolerate frosts and should be overwintered unless you live in the warmest tropical US hardiness zones. The other differences are that tropical waterlilies have scalloped edges, compared to smooth edges seen on hardy types, and tropical varieties come in a wider range of colors.
How to Overwinter Tropical Waterlilies
Kathy Jentz advises letting the waterlily be left to go through one or two frosts, as ‘the cool weather helps force dormancy’ and prepares it for the overwintering process. Stopping fertilizing plants around two months before the first frost is due also helps the waterlily prepare for entering dormancy.
‘After the first or second frost, remove the plants and cut them back,’ recommends the expert. Take the waterlily and its planting basket out of the garden pond, and find the plant’s tuber from just below the crown. The tuber is small and hard, up to golf ball size, and should be separate from the plant’s root structure.
Gently clean and dry the tuber, before trimming off any remaining roots or stems, so it is ready for storage. As for where to overwinter the tender plants, Kathy says: ‘Store the tubers in a cool, dark place in a plastic bag with moist sand.’
An ideal place to overwinter tropical waterlilies is in a dark area with temperatures of 55-60°F during winter, such as a garage, basement, closet, or crawl space. The main alternative to moist sand is keeping them in sphagnum moss (which can be purchased as bags of sphagnum moss on Amazon), and you can use a glass container instead of a plastic bag if you prefer.
It is advisable to check the stored tubers over the winter to ensure that they do not dry out completely. If they do look dry, spritz the sand or moss with water to rehydrate the tubers.
Come spring, bring the tuber out of storage and place it in a 3-4 inch pot with aquatic soil, such as this pond plant potting media at Walmart. Keep it in a container of water with a temperature of 60-65°F, in a spot that gets lots of direct sunlight. You can use grow lights on plants to supplement the natural levels.
Once the outside pond water temperature reaches 70°F, the tropical lily can be transferred into a larger pot, given some fertilizer, and submerged in its summer home.
Kathy Jentz is the editor of the Water Garden Journal for the International Waterlily and Water Gardening Society. She is also editor and publisher of the award-winning Washington Gardener Magazine, based in Washington, DC.
FAQs
Should You Cut Back Waterlilies in Winter?
It is recommended to cut back waterlilies in winter. When the foliage dies back as the plant enters dormancy, it is best cut back to just above the rhizome. This is beneficial as decaying plant material increases the nutrient levels in the water, which encourages the development of algae and can impair the water quality.
Water lilies can make a great plant for a natural swimming pool, as they are both beautiful and practical, as their leaves cover a large area to prevent algae blooms. Other fantastic options include valisneria, an excellent oxygenator, and hornwort, which absorbs nutrients to reduce the growth of algae.
A liquid fertilizer specially formulated for hardy and tropical waterlilies. It helps promote the development of large blooms, impressive pads, and healthy roots.
A set of three four-inch square slotted plastic baskets suitable for all kinds of aquatic plants.
A live 4"-8" Nymphaea 'Purple Joy' tuber to grow for a tropical plant with white flowers tipped with purple.
