Daylilies are winter hardy to United States Department of Agriculture plant hardiness zone 3 and there is no need to dig them up and store them during the winter months. However, apply about 4 inches of organic mulch, such as straw or shredded leaves, for newly planted or divided daylilies, especially in USDA zones 3 to 5. On the other hand, if you obtain daylilies and are not ready to plant them immediately, store them until you are ready. Ideally, daylilies should only be stored for a short period of time, according to the University of Vermont Extension.
Dig up daylilies in zones 1 and 2 after the first frost. Cut off the foliage first and then carefully use a trowel or garden fork to dig around the plants. Lift up the roots, which are planted just inches below the soil’s surface.
Fill a container with moist sand or peat moss and bury the daylily roots in the container. Store the daylily roots you dug up or those you are not ready to plant.
Set the container in a cool location, such as in your garage or crawl space, until you can plant them. In zones 1 and 2, replant them after the last frost. In warmer zones, plant them as soon as possible—that is, as soon as the ground is workable.
Check on your daylilies every 2 to 3 weeks. If you notice the sand or peat moss becoming dry, add a bit of water to moisten it. If you notice mold or fungi on the roots, dip the plants in a fungicide solution designed to prevent root rot. Then change out the sand or peat moss and return the daylilies back to storage. Check on them more frequently once they have been treated with fungicide.