The question of how many types of lilies exist has two distinct answers: one based on natural science and the other on horticultural practice. A “true lily” belongs exclusively to the genus Lilium, a group of perennial flowering plants that grow from bulbs. This botanical definition separates them from many other garden favorites that use the common name “lily,” such as Daylilies or Calla lilies. Classification complexity arises because the count must account for both naturally occurring species and the thousands of hybrids created by breeders.
The Botanical Answer: Species and Natural Variation
The scientific count focuses on distinct, naturally occurring populations recognized as species. Botanists generally agree that the genus Lilium contains over 100 recognized species, typically falling between 110 and 120 accepted species. These species are distributed across the Northern Hemisphere, growing in temperate climates that extend into the subtropics. The greatest concentration and diversity are found in Asia, particularly in China and the Himalayas, which is considered the genus’s center of origin.
These natural species exhibit significant variation in size, color, and flower shape, demonstrating the genetic material available for breeding. North America and Europe host fewer native species than Asia, but feature unique characteristics, such as the rhizomatous bulbs found in some North American types. A species reproduces naturally, while a cultivar is a plant selected and maintained by humans for desirable traits, often through hybridization. Cultivars are designated with a name in single quotes, such as Lilium ‘Stargazer’, distinguishing them from their wild species ancestors.
The Nine Horticultural Divisions
The sheer number of hybrids necessitated a practical classification system for gardeners and commercial growers, organized into nine Horticultural Divisions. Established by the Royal Horticultural Society, this system groups lilies primarily by species parentage, flower shape, and blooming season. Divisions I through VIII are dedicated to hybrids, while Division IX contains all the pure, unhybridized species.
The most widely grown types belong to the first division, the Asiatic Hybrids, prized for their early blooming, wide color range, and ease of cultivation. Asiatic flowers are generally unscented and can face upward, outward, or downward. Martagon Hybrids (Division II) are distinguished by whorled leaves and small, downward-facing flowers with strongly recurved petals, often called a “Turk’s cap” shape. These hybrids are notable for their tolerance of partial shade.
Division VII, the Oriental Hybrids, are famous for their large, showy blooms and intense, sweet fragrance. They typically bloom later than Asiatics and are derived from species like Lilium auratum and Lilium speciosum. Division VI, the Trumpet and Aurelian Hybrids, are tall, stately plants with deep, trumpet-shaped flowers that release their strong scent primarily in the evening. Recent breeding efforts produced Division VIII, the Interdivisional Hybrids, which combine traits from previously incompatible groups, such as the popular LA Hybrids (Longiflorum x Asiatic) and OT Hybrids (Oriental x Trumpet).
Understanding Lily Bulb Types
Beyond the visible flower characteristics, lilies are also classified by a fundamental difference in their subterranean structure: the nature of their root system. All true lilies grow from a bulb composed of overlapping, fleshy scales that lack the protective papery covering, or tunic, seen on tulips and daffodils. These tunicless bulbs are vulnerable to drying out and require careful handling before planting.
The crucial distinction lies in where the plant develops its roots, which directly influences planting depth. Basal-rooting lilies produce roots only from the bottom of the bulb (the basal plate), primarily serving to anchor the plant. In contrast, the majority of hybrid lilies are stem-rooting, producing two sets of roots. One set is the basal roots for anchoring, and the second set, the stem roots, emerge from the stem just above the bulb.
The stem roots are the primary “feeder” roots, absorbing most of the water and nutrients that support the tall flowering stalk. Stem-rooting varieties must be planted deep—at least two to three times the bulb’s height—to allow the stem to develop these essential feeder roots in the cool, moist soil. This morphological feature is a significant factor in successful lily cultivation, ensuring the plant has the robust root system necessary for substantial growth.