Some daylilies are evergreen while others will die back in the winter (these are called "dormant" varieties). While dormant-type daylilies need winter protection only their first winter in the ground, evergreens should be protected every winter for the life of the plant. Gardeners that live in heavy winter areas are fortunate as a blanket of snow acts as a natural insulation against biting winds and harsh cold. Gardeners in milder winter areas will need to take precautions and protect their daylilies from a hard freeze.
Discontinue watering the daylily at the season's first hard freeze.
Refrain from cutting back the daylily's leaves as winter approaches. Foliage acts as a natural insulation for the plant.
Apply a 4- to 5-inch layer of light mulch (pine needles or straw, for instance) over the daylily immediately following the first hard freeze. Remove the mulch in the spring after all danger of frost has passed.