The lily, with its trumpet-shaped flowers, is a popular choice for gardens and bouquets. Many people assume this dramatic flower must be replanted annually, leading to confusion about its long-term viability. This article clarifies the lifecycle of the lily and confirms the nature of its persistence in the garden.
What Defines a Perennial Plant
A perennial plant is defined botanically as any plant that lives for more than two growing seasons. This classification contrasts with annual plants, which complete their entire life cycle in a single season, and biennials, which require two seasons to flower and set seed before dying. Perennials have evolved mechanisms to survive periods when conditions are unfavorable, such as the freezing temperatures of winter or the intense heat of a dry summer.
The ability of a plant to persist across multiple years depends on its specialized underground storage structures. These structures, which can take the form of bulbs, tubers, rhizomes, or thick woody crowns, store energy in the form of carbohydrates produced during the growing season. When the above-ground foliage dies back, the stored energy allows the plant to enter a state of dormancy, only to regrow from the same rootstock when favorable weather returns.
Lilies and Their Perennial Nature
True lilies, which belong to the genus Lilium, are definitively perennial plants that return to bloom annually. They achieve their longevity by growing from a specialized underground storage unit known as a true bulb. This bulb functions as the plant’s survival organ, retaining the energy and genetic material needed to produce a new flowering stem each spring.
The lily bulb structure is unique among many common garden bulbs, as it is composed of overlapping, fleshy scales and lacks the protective, papery outer layer, or tunic, found on plants like tulips. This “scaly” nature means lily bulbs are more vulnerable to drying out and must remain in the moist, cool environment of the soil to survive. They are designed to be permanent fixtures in the garden, increasing in size and often producing small offset bulbs, called bulblets, over time.
Many plants are commonly called “lilies” despite not belonging to the Lilium genus, such as Daylilies (Hemerocallis) and Calla Lilies (Zantedeschia). Both are perennial, but their underground structures differ. Daylilies, for instance, grow from fibrous roots or rhizomes rather than a true scaly bulb.
Preparing Lilies for Dormancy
Because the lily’s perennial nature relies entirely on the survival of its underground bulb, proper end-of-season care is necessary to ensure its return. The most important action is allowing the above-ground foliage to complete its natural life cycle. After the flowers fade, the leaves remain green and continue the process of photosynthesis, which is how the plant manufactures carbohydrates.
This energy is transferred down the stem and stored within the bulb, fueling the next season’s growth and flower production. Cutting back the green stem prematurely is counterproductive, as it starves the bulb of the energy needed to survive winter and bloom the following year. Gardeners should wait until the stem and leaves have completely yellowed and turned brown before cutting them back to the soil line.
Once the foliage has been removed in late fall or early winter, applying a thick layer of mulch provides insulation for the bulb. This layer helps regulate soil temperature, delaying the deep freeze in colder climates. Lilies are dormant during the winter, so watering should be stopped completely, as excessive moisture combined with cold temperatures can cause the scaly bulb to rot.