Hardy water lilies are an investment plant, usually running between $30 and $50 a plant at the nursery or garden center. With that in mind, overwintering them is a wonderful way to build your lily collection and conserve your garden funds. I peeked at my overwintering lilies this week, and they are all showing new growth… just enough to know they’re alive.
If you pull your water lilies before your pond or water feature freezes, then keep them wet, dark and between 55 degrees and freezing throughout the winter, your lilies will slow way down, take a nap, and be ready for you the following spring. If you have a fridge in the garage or basement, this could work. I am fortunate enough to have a root cellar situation in my old house basement, and I place my lilies in 5 gallon pails, cover them and set them against the wall of the cellar. I keep a thermometer on the pail to monitor the temp. Before bringing your lilies in for the winter, cut back all the foliage.
As soon as temps are consistently over freezing at night, you may bring your lilies outside. Keep them out of the direct sun until they go into the water, which in zone 4, is after Memorial Day. Water lilies need full sun to bloom the way that God meant them to.