Despite their common names, Daylilies and True Lilies belong to entirely different botanical families, which is the most fundamental distinction. True Lilies are members of the genus Lilium within the family Liliaceae. This genus includes classic species and hybrids like Easter Lilies, Asiatic Lilies, and Oriental Lilies. In contrast, Daylilies are classified under the genus Hemerocallis and belong to the family Asphodelaceae. This separate taxonomic lineage highlights a significant evolutionary divergence, meaning they are more distantly related than their common names suggest.
The underground storage organs of these plants are a key identifying feature. True Lilies grow from true bulbs. A bulb is a complex structure consisting of modified leaves (scales) attached to a basal plate, which contains the following season's plant embryo and stored nutrients. This is analogous to an onion. Daylilies, however, possess a fibrous root system with thickened, tuberous roots (rhizomes). These fleshy roots store energy but lack the specialized layered scale structure of a true bulb. This difference in structure influences their propagation and how they spread in a garden setting.
The growth pattern and leaf formation of the two plants are markedly different. True Lilies typically produce a single, central, unbranched stem (scape) that grows from the bulb. Leaves form in whorls or spirals directly along the length of this stem. Daylilies exhibit a clumping growth habit. Their leaves are basal, meaning they grow in a grass-like clump or fountain directly from the crown of the plant at soil level. The flower scapes of Daylilies are leafless and rise separately from this leafy base.
While both produce showy, often trumpet-shaped flowers, their floral anatomy and longevity differ greatly. True Lily flowers are complex, with six petals/tepals often adorned with spots or streaks. They possess six distinct stamens and a single prominent pistil. Each individual True Lily flower can last for several days to over a week on the plant. The name "Daylily" refers directly to its flower's ephemeral nature; each individual blossom opens in the morning and withers by the following evening. However, each scape produces numerous buds, providing a long bloom period.
This is a critical difference for gardeners with pets. True Lilies (Lilium spp.) are highly toxic, especially to cats. Ingesting any part of the plant, including pollen or the water from the vase, can cause acute kidney failure and be fatal. Daylilies (Hemerocallis spp.), on the other hand, are not toxic to humans or most animals. In fact, their buds and flowers are edible and are used in some culinary traditions. It is crucial to note that while Daylilies are safe, other look-alike plants are not, so proper identification is always essential.
