Daylilies are generally easy plants to grow, but they often succumb to overcrowding and sometimes disease can be an issue. Daylilies can get shaded out by growing trees and bushes. On the other hand, you may have pruned them a bit too early and too much. These are some of the common reasons why your daylilies will not bloom, and are fortunately, you can easily remedy them.
If your daylilies have bloomed beautifully in past years, chances are they have multiplied and are now overcrowded. Daylilies typically need to be divided every three to four years, usually in the fall after blooming. If none are blooming, divide them in the fall anyway. Pull the plants apart so each root section has two or three fans of foliage. Replant so the tops of the root sections are 1 inch below the soil and space plants 18 to 24 inches apart.
Daylilies need lots of sunlight to bloom to their fullest potential. At a minimum, daylilies need at least six hours of sunlight a day. Transplant daylilies to another area of your garden or trim back some trees or bushes so they can receive more light.
Ideally, you should leave the foliage on daylilies after blooming until it browns or dies back. This gives it the most amount of time to absorb sunlight, which it converts into sugar and uses for energy. If you’re in the habit of cutting back the foliage too soon, you may be depriving the plants of much-needed energy to make next year’s growth and blooms. On years that you divide plants after blooming, you can cut back the foliage to 5 to 6 inches to make digging them up and dividing easier.
Common daylily diseases that can prevent blooming include leaf streak and crown and root rot. Aureobasidium microstictum is the most common leaf spot disease for daylilies and likely started the previous year. It is evident by dark green or brown discoloring, streaky or spotty leaves. The best thing to do is prune the infected foliage to the ground to prevent further spread and divide plants if your garden is overcrowded. If your crowns or roots are rotting, the soil is too soggy or the bottoms of your plants are discolored, you have rot. To treat, cut off the infected part of the crown or roots and improve soil drainage by incorporating some organic matter into the soil. Note that your daylilies may not bloom until the next year or two after treating them for diseases.