Yes, true lilies do have bulbs, and these underground storage organs are the defining feature that botanically classifies them within the genus Lilium. These perennial plants rely on their specialized subterranean structure to store the starch and nutrients required to survive dormant periods and fuel the next season’s growth. The presence of this specific type of bulb is what differentiates a true lily from the many other flowering plants that share the common name “lily.”
What Makes a True Lily Bulb Unique
The anatomy of a Lilium bulb is distinct from common garden bulbs like tulips or onions because it lacks a protective outer layer. While most bulbs are classified as “tunicate” bulbs, possessing a papery tunic or skin, the lily bulb is “non-tunicate,” or “scaly.” This means the fleshy, modified leaves, known as scales, are loosely overlapping and fully exposed.
These scales are plump and succulent, designed to act as the primary storage repository for the plant’s energy reserves. The scales attach to a small, compressed stem at the base of the bulb, called the basal plate, where the roots emerge. Because the bulb lacks a protective tunic, it is prone to drying out quickly and is more susceptible to physical damage. This unique, naked structure is the biological fingerprint of a true lily.
Why Not All “Lilies” Have Bulbs
The common name “lily” is frequently applied to plants that are not part of the Lilium genus, leading to widespread confusion about their subterranean structures. Many popular garden plants use different storage organs that serve a similar purpose but are anatomically distinct from a true bulb. The Daylily (Hemerocallis), for example, grows from fleshy, tuberous roots or rhizomes rather than a true bulb.
Similarly, the Calla Lily (Zantedeschia) and the Canna Lily (Canna) utilize thick, horizontal underground stems called rhizomes. Unlike a bulb, which is made of modified leaves, a rhizome is a stem structure with nodes and buds that grows horizontally.
Caring for Lily Bulbs
The scaly, non-tunicate structure of the lily bulb dictates specific planting and care requirements to ensure its health. Because the bulb scales are naked and hold a lot of moisture, proper drainage is necessary to prevent fungal rot. Waterlogged soil will cause the fleshy scales to decay, which is why planting in raised beds or well-amended soil is often recommended.
Lily bulbs should be planted at a substantial depth, typically between 4 to 9 inches, depending on the variety and size of the bulb. This deep planting encourages the development of “stem roots,” which emerge from the stem above the bulb and are responsible for most of the plant’s nutrient and water absorption. It is also important to avoid letting the bulb dry out before planting, as the lack of a tunic means moisture is lost rapidly.