Daylilies are a common sight in gardens, recognized as a resilient perennial that produces a profusion of vibrant, trumpet-shaped flowers. Belonging to the genus Hemerocallis, these plants are popular for their ease of growth and ability to thrive in a wide range of conditions. Despite their widespread popularity, many gardeners remain unsure about the subterranean structure that supports this hardy plant.
Daylily Root Structure and Classification
Daylilies do not grow from true bulbs, despite the frequent use of the term “daylily bulbs” in commerce. The plant grows from a central structure called a crown, which is compressed stem tissue located where the foliage meets the underground root system. This crown is the base from which the leaves emerge in fan-like arrangements and where the roots originate.
The roots are classified as fleshy, tuberous roots, forming a dense mass beneath the crown. These specialized roots function primarily as storage organs, swelling to hold water and starches for the plant to draw upon during periods of stress or dormancy. This robust root system contributes to the daylily’s toughness and drought tolerance once the plant is established.
Unlike a true bulb, this structure is composed of modified root tissue rather than layered leaf tissue. The genus Hemerocallis is defined by this clump-forming, herbaceous perennial habit. The daylily’s resilience and ability to survive being out of the ground for an extended time are directly related to the reserves stored within these fleshy roots.
Defining True Bulbs
A true bulb is a specific botanical structure that differs fundamentally from the daylily’s root system. It is a modified stem surrounded by fleshy, layered scales, which are essentially modified leaves. These layers, like those seen when slicing an onion, contain the stored food supply and protect the embryonic plant inside.
True bulbs, such as those found in tulips, daffodils, and hyacinths, contain the entire structure for the next season’s growth, including the miniature flower bud. The base of the bulb is a flattened disc called the basal plate, where the roots emerge. Many true bulbs are also protected by a dry, papery outer layer called a tunic, which helps prevent dehydration during dormancy.
This layered design allows the plant to survive its dormant period by packaging all necessary resources within a single, self-contained unit. The contrast between this layered structure and the daylily’s mass of separate, tuberous roots highlights the difference in their botanical classification.
Planting and Care Based on Root Structure
Understanding the daylily’s crown and tuberous root structure is important for successful planting and long-term care. When planting, the crown must be positioned correctly to prevent rot or drying out. The crown, where the roots and the leaves join, should be set at the soil level or no more than one inch below the surface.
Planting daylilies too deeply buries the crown and can cause the plant to rot, while planting too shallowly can expose the fleshy roots to drying air. Gardeners should dig a hole wide enough to allow the fleshy roots to be spread out naturally, often over a small mound of soil in the center of the hole. This method ensures that the roots are directed downward and outward, which is crucial for establishing the plant.
The clumping nature of the crown dictates the method for propagation, which is typically done through division rather than separating bulb offsets. Every few years, when the plant clump becomes overly dense, the entire mass of roots must be dug up and physically separated into smaller sections. Each new division, or “fan,” must include a portion of the crown and a healthy mass of the thick, tuberous roots to ensure the plant can survive and regrow. The durability of the tuberous roots means daylilies can be transplanted with a high success rate, as the stored nutrients provide a buffer during the re-establishment period.