To properly winterize daylilies, trim away browning and dead leaves and blooms before the first frost to protect root balls. Winterizing may also include thinning large clumps and clearing dirt away from the base of any foliage. You should also mulch to protect daylilies from freezing in colder climates.
Whether your daylilies go dormant in the winter or are evergreen varieties, they need seasonal care to winterize them. First, trim away dead foliage, because it can wick water down into the root mass, causing rot. Also, inspect the plant bases, and clear away any built up dirt.
Since many varieties of daylilies form large clumps, you may want to dig up and separate the largest into smaller root balls, especially if the plants haven’t produced many blooms because they’re too crowded. Dig about a foot away from the base to get the whole root mass without damaging any nodes. Then, separate and replant the individual lily roots. Your plants should produce more and better roots the next season.
To protect the roots for the winter, mulch lily beds with about 2 inches of organic materials such as pine straw, oak litter or sterile compost. Further, continue watering lily beds through the fall and winter.