The question of whether daylilies are evergreen cannot be answered with a simple yes or no, as the genus Hemerocallis encompasses a wide spectrum of foliage behaviors. Daylilies are resilient, clump-forming perennials known for their trumpet-shaped flowers, each bloom lasting only a single day. Their ability to thrive across many climates is directly tied to an inherent genetic trait that dictates how their leaves respond to the colder months of the year. This foliage behavior is a primary characteristic used in classifying the thousands of modern daylily cultivars available to gardeners.
The Three Types of Daylily Foliage
Modern daylilies are classified into three distinct categories based on their genetically determined foliage habits: dormant, evergreen, and semi-evergreen.
Dormant Daylilies
The Dormant type exhibits deciduous behavior, meaning the foliage completely yellows and dies back to the ground after the first hard frost of the season. This type forms a resting bud just below the soil surface, which protects the plant’s growth point until spring warmth returns. This process requires a period of winter chilling to trigger robust spring growth.
Evergreen Daylilies
Evergreen daylilies are genetically programmed for continuous growth, attempting to retain their leaves throughout the year. They do not form a resting bud and continually push up new foliage from the crown, even during mild winter spells. In warmer climates, such as the deep South, the leaves of these cultivars can remain green all winter long, though the growth rate slows significantly.
Semi-Evergreen Daylilies
The Semi-Evergreen classification serves as a middle ground for cultivars whose behavior is not strictly dormant or evergreen. This intermediate type often retains some of its foliage through the winter in milder climates but may die back completely in response to sustained freezing temperatures.
Regional Impact on Foliage Behavior
While a daylily’s foliage type is an inherent genetic trait, the local climate can significantly override its programmed behavior. Evergreen varieties, ideally suited for warm climates like USDA Hardiness Zones 9 and 10, may struggle when planted in colder regions like Zone 4 or 5. In these northern zones, persistent sub-freezing temperatures freeze the foliage back, causing it to turn mushy and die, essentially forcing the evergreen plant into a temporary dormancy.
Conversely, Dormant daylilies require a cold period to perform optimally and may fail to thrive in the warmest climates that do not experience a hard winter. Without the necessary chilling hours, the plant’s internal clock for spring growth is disrupted, leading to a loss of vigor and potentially fewer blooms.
The semi-evergreen types are the most dramatically affected by regional differences, often behaving as true evergreens in southern gardens but fully dormant in northern ones. This variability highlights that the foliage classification is more of a spectrum than a set of rigid categories.
Seasonal Care Adjustments
The practical care for daylilies in the autumn and winter should be tailored specifically to their foliage type to ensure their health.
Dormant daylilies are the easiest to manage, as their foliage naturally dies back completely after a hard frost. Gardeners can cut the dead leaves back to within a few inches of the ground in late fall or wait until early spring before new growth emerges.
For the evergreen and semi-evergreen types, the winter care routine is slightly more involved, particularly in regions that experience freezing weather. Since these plants attempt to retain their leaves, the foliage that freezes will turn brown and soft. This damaged, mushy foliage should be trimmed back to prevent rot from settling into the crown and helps reduce the risk of disease over winter.
In colder hardiness zones, a layer of organic mulch, such as straw or shredded leaves, should be applied around the crowns of all daylilies, especially evergreen varieties. This protective layer is not meant to keep the plant warm, but rather to minimize the freeze-thaw cycles in the soil that can push the crown out of the ground, a process known as heaving.