Lilium nepalense

Lilium nepalense

D. Don, 1821
Nepal lily

Overview

Section: Sinomartagon, subsection c (S5c)
Origin: Indomalaya (Sikkim, Kuamon, Kalimpong districts of northern India, Nepal, Bhutan, Myanmar, Yunnan province of China, Laos, Vietnam)
Habitat: Steep cliffs in cloud forest mountains
Type: Subalpine Asiatic
Status: fairly common

Introduction

Lilium nepalense is one of the most widespread and variable lilies in the Indomalayan region, extending from northeastern India and Nepal through Bhutan and Myanmar into Thailand, Laos, Vietnam, and the southwestern provinces of China. Although well known in cultivation, the plants commonly grown under this name represent only a narrow slice of the species’ actual diversity. In the wild, L. nepalense forms a vast and diverse complex of regional types, subspecies, and local phenotypes that remain poorly understood. This ambiguity has made the species one of the most taxonomically difficult members of the genus Lilium. What is grown in Europe and North America today largely reflects a single southern geographic form rather than the full breadth of variation present across its enormous range.

Description

Lilium nepalense is one of the most distinctive and easily recognized members of the Sinomartagon lilies, notable for its elegant, down-facing trumpets and the remarkable range of color forms found across its wide geographic distribution. The bulb is a flattened globe composed of broad, fleshy scales tinged in pink to deep purple, often producing long stolons that allow the plant to emerge at some distance from the parent, an adaptation well suited to life on unstable mountain slopes. From this bulb the plant sends up a slender but sturdy stem that can range from one to five feet in height depending on the locality, soil, and climatic conditions. The stem is typically clothed in narrow, lanceolate leaves arranged irregularly or in loose whorls, giving the plant a graceful, airy appearance.

The flowers are the defining feature of the species. Each stem typically bears one to three blooms, though exceptional plants may produce more. The flowers are long-tubed and nodding, with a gently flared mouth and slightly recurved tips. Their coloration varies dramatically across the species’ range: in Bhutan, Nepal, and the northern Himalaya, the flowers are often yellow-green with a strong, dark maroon to purple throat; in Assam, the rare var. concolor lacks throat pigmentation entirely, producing clear yellow or greenish blooms; farther south in Myanmar, Laos, and Thailand, flowers may be narrower, lighter, or more lemon-toned, with varying degrees of spotting or shading. This extraordinary variability has historically led botanists to misclassify many populations as separate species, though modern genetic work suggests these differences represent ecotypes within a single lineage.

The flowers emit a powerful, sweet fragrance that intensifies at night, an adaptation for pollination by hawk moths (Sphingidae), which hover beneath the blooms to access the nectar deep within the tube. The ovary matures into a three-parted capsule containing numerous narrow, winged seeds that ripen in late summer. Germination is immediate and epigeal, beginning soon after dispersal when temperatures and moisture align with the onset of the monsoon season. The overall form of the plant, a stoloniferous bulb, slender stem, nodding trumpets, and wide palette of green, yellow, and purple tones—makes Lilium nepalense unlike any other lily in cultivation, a species whose morphology reflects the complex climates and mountain ecosystems from which it arises.

Infraspecific Variation

Although Lilium nepalense is one of the most variable lilies in the Indomalayan region, modern taxonomy recognizes only two formal varieties within the species. The typical form, Lilium nepalense var. nepalense, corresponds to the autonym and includes the broad range of Himalayan plants from Nepal, Bhutan, and northeastern India. This variety is almost certainly the form represented by the original type specimen collected by David Don in 1821 and encompasses most of the robust, green-yellow forms with strongly pigmented purple throats that dominate both wild populations and cultivated material.

The second accepted variety, Lilium nepalense var. concolor, was described by A. N. Cotton in 1937 and is distinguished by its entirely unmarked flowers, which lack the maroon or purple throat pigmentation typical of other Himalayan forms. This variety occurs primarily in Assam and adjacent areas, and remains the only infraspecific taxon considered morphologically and geographically consistent enough to warrant formal recognition.

Despite the immense diversity observed across its range, no subspecies are currently recognized, and nearly all other names historically applied to this complex, such as Lilium primulinum in its various forms, Lilium majoense, and Lilium poilanei, are no longer treated as distinct species. Modern molecular research, including complete chloroplast genomes, nuclear ITS sequencing, and multilocus genomic studies, has demonstrated that all of these supposed species fall well within the genetic boundaries of Lilium nepalense. They do not form separate evolutionary lineages, and instead represent regional or ecological variants shaped by elevation, climate, and local environmental conditions. The horticultural name “robustum,” widely used for the vigorous Nepal-Bhutan form common in cultivation, is similarly unrecognized botanically and reflects only a horticultural selection rather than a taxonomic entity. Collectively, these findings indicate that Lilium nepalense is best understood as a single, genetically cohesive species with numerous local expressions rather than a group of separate species.

Range and Distribution

The Nepal Lily is native to the Indomalayan realm, where it occupies a broad arc of mountainous and subtropical habitats. It occurs in Nepal, Bhutan, the Kalimpong and Sikkim districts of India, Assam, northern Myanmar, northern Thailand, Laos, Vietnam, and Yunnan Province in southwestern China. Most cultivated material has historically come from the narrow corridor between Sikkim and Kalimpong, which means Western horticulture has long been familiar with only one of many regional expressions of the species. Material from China, especially from southern Yunnan, represents an even smaller fraction of its true diversity. Because of this, modern cultivation provides a skewed impression of what Lilium nepalense is and what it may ultimately prove to be once its taxonomy is fully resolved.

Taxonomic Complexity

The Lilium nepalense complex is widely regarded by botanists as one of the most problematic taxonomic puzzles within the genus. David Don’s original type specimen, collected in 1821 near what is now Langtang National Park in Nepal and preserved at Kew Gardens, remains the baseline for the name. Yet the form most often grown in gardens today does not necessarily match Don’s specimen. This discrepancy highlights how difficult it is to establish a single “typical” form of a species that varies markedly across geography, climate, and elevation.

Several lilies described from the same general region, such as Lilium primulinum var. burmanicum, Lilium primulinum var. ochraceum, Lilium majoense, and Lilium poilanei, may in fact represent nothing more than ecological or geographic variations of L. nepalense. Some authorities argue that the most widespread variant, historically called Lilium primulinum var. burmanicum, should actually be redefined as Lilium nepalense var. nepalense, and that the remaining forms should be treated as varieties within a single, highly polymorphic species. At present only two varieties, Lilium nepalense var. concolor and Lilium nepalense var. robustum, are formally recognized, but these designations do not come close to reflecting the extraordinary variability encountered in the wild.

Habitats and Ecosystems

Lilium nepalense inhabits steep, forested mountain slopes and rocky escarpments at elevations generally between 2,000 and 3,000 meters (6,600 to 9,800 feet). Its range overlaps the Himalayan Subtropical Broadleaf Forest ecoregion, an area defined by dramatic terrain, intense monsoon cycles, and a mixture of evergreen and semi-evergreen forest types. It grows from alluvial deposits rich in humus and lime, from acidic podzolic soils found beneath montane forests, and from shallow rocky substrates where drainage is rapid and root systems cling to crevices. In the lower foothills it may occur near the margins of the Terai-Duar savannas, while at higher elevations it approaches the Himalayan subtropical pine forests. Its ability to thrive in such a wide range of soil and climate conditions demonstrates the ecological breadth that contributes to its immense morphological diversity.

The climate of this region is governed almost entirely by the annual monsoon. Summer brings heavy rainfall between June and September, often delivered in intense storms that drench the mountains with 250 to 450 mm (9 to 18 inches) of rain each month. Winter, by contrast, is dry and cold, with temperatures at higher elevations regularly dropping below freezing. This cycle of wet, turbulent summers and cool, dry winters is essential to understanding the species’ behavior and needs, both in the wild and in cultivation.

Morphology and Identification

Lilium nepalense produces a flattened, globe-shaped bulb composed of broad purple-pink scales. The stems are frequently stoloniferous, traveling underground before emerging some distance from the parent bulb. Mature plants typically reach heights of 90 to 150 cm, although larger forms occur. The flowers are distinctive, long-tubed, and down-facing, with colors ranging from green to cream or yellow, and with throats marked by deep purple or maroon pigmentation. In the variety concolor, the flowers are entirely greenish-yellow without any throat coloration. Plants usually carry one to three blooms per stem, though exceptional specimens may produce as many as five. The flowers emit a strong evening fragrance, attracting hawk moths (Sphingidae), which serve as the primary pollinators. Seeds are narrow-winged, pale brown, and germinate immediately in an epigeal manner during late spring or early summer.

Cultivation

Despite its origins in subtropical and monsoon-driven climates, Lilium nepalense has proven surprisingly adaptable and has been grown successfully in regions such as Germany and the Pacific Northwest of the United States. The key to success lies in replicating its natural cycle of heavy summer moisture and cool, dry winters, combined with exceptional drainage and steady airflow. This lily naturally grows on steep slopes and cliff faces where excess water drains immediately and where mountain winds provide constant ventilation. In cultivation, it resents stagnant air and wet soil, especially during the winter dormancy period. Gardeners often encounter difficulties not because the species is tender but because the moisture cycle is inverted relative to most Western climates.

When provided with a raised bed, a well-drained slope, or a deep sand-gravel mixture, Lilium nepalense can be remarkably vigorous. Its diverse geographic origins mean that different forms may prefer slightly different conditions, but all share a need for rapid drainage, ample summer moisture, and free circulation of air. The majority of cultivated plants belong to a vigorous northern form often identified as robustum, while material from Myanmar, Thailand, and southern Yunnan, with their narrower, lighter flowers, remains rare in Western horticulture. The extraordinary variability seen in wild photographs, especially from Bhutan, Nepal, and northern Myanmar, highlights how poorly the cultivated strain represents the species as a whole.

Phenotypic Diversity

Plants labeled as Lilium nepalense can look strikingly different depending on their origin. The robust, yellow-green forms of Sikkim and Bhutan differ markedly from the pale, narrow-tubed southern forms found in Myanmar and Thailand. In Assam, the concolor variety presents an entirely unmarked greenish-yellow flower, while Chinese forms tend to resemble southern variants rather than the Himalayan types. Several wild Thai forms historically described as separate species, such as L. poilanei, fit naturally into the continuum of the broader nepalense complex. Photographs from Bhutan show at least two distinct regional expressions, one matching the typical robust variety and another representing the unmarked concolor type. This diversity suggests that the species occupies a far wider morphological spectrum than previously imagined and may ultimately require a revised classification once comprehensive DNA studies are completed.

Genetic and Genomic Research

Modern genetic research has significantly clarified the position of Lilium nepalense within section Sinomartagon and has provided strong support for the long-held suspicion that several closely related “species” described from the Himalaya and Indochina are not distinct species at all, but regional variants of a single, highly polymorphic lineage. Complete chloroplast genome studies from multiple populations in Nepal, Bhutan, Yunnan, and Myanmar show that L. nepalense forms a single, tightly clustered genetic group, despite the dramatic morphological variation across its range. These plastomes vary only slightly in size and structure and share nearly identical gene content, strongly suggesting a cohesive species rather than multiple independently evolving lineages.

Nuclear ITS phylogenies tell a similar story. Early nuclear ribosomal DNA studies placed L. nepalense deeply within a Sinomartagon clade that also includes L. taliense, L. bakerianum, and L. duchartrei, but they did not separate the various regional “species” such as majoense, poilanei, or primulinum into their own stable clades. Instead, these forms intermingle genetically with L. nepalense, indicating that morphological differences do not reflect ancient divergence. This picture became clearer with the 2017 multilocus genomic analysis of Lilium, which demonstrated extensive gene flow across Sinomartagon species boundaries, creating blurred taxonomic divisions and making morphology alone a poor predictor of evolutionary history. In that study, L. nepalense formed a well-supported group but absorbed nearby forms rather than excluding them, exactly what would be expected of a geographically variable species complex.

Population-level studies from Yunnan reinforce this interpretation. These analyses found high genetic diversity within populations of L. nepalense but relatively low differentiation between populations, even when plants displayed markedly different phenotypes. This pattern is characteristic of a single species spread across diverse ecological gradients, not of several species evolving independently. Chromosome studies also show variation within L. nepalense populations but no consistent karyotypic boundaries that would justify dividing the species.

Taken together, this body of research strongly supports the view that Lilium nepalense, Lilium primulinum (in all its varieties), Lilium majoense, and Lilium poilanei represent a single phylogenetic lineage composed of multiple local forms. These plants form a continuum shaped by geography, altitude, seasonal climate, and soil type rather than by reproductive isolation. While the most extreme southern Indochinese forms may eventually warrant recognition as ecotypes or subspecies, the current molecular evidence does not support treating them as full species.

GENUS LILIUM
│
└── Section SINOMARTAGON
│
├── Clade A: Himalayan–Indochina Complex
│ │
│ ├── Lilium nepalense (sensu lato)
│ │ ├── var. nepalense
│ │ ├── var. concolor
│ │ ├── “robustum” horticultural form
│ │ ├── L. primulinum var. burmanicum (nested within)
│ │ ├── L. primulinum var. ochraceum (nested within)
│ │ ├── L. majoense (nested within)
│ │ └── L. poilanei (southernmost variant)
│ │
│ └── Sister lineage: Lilium taliense + Lilium duchartrei
│
├── Clade B: Yunnan–Sichuan Sinomartagon Group
│ L. bakerianum
│ L. lankongense
│ L. wardii
│ L. mackliniae (more distant but within section)
│
└── Clade C: Northeastern Sinomartagon species
L. leichtlinii
L. medeoloides
L. dauricum

Cultivation

In cultivation, Lilium nepalense proves far more adaptable than its exotic origins suggest, provided that its fundamental ecological needs are respected. In its native range, the species grows on steep, well-drained slopes, forest margins, and rock faces across the Himalayan and Indomalayan mountains, where summer monsoon rains deliver heavy moisture followed by cool, dry winters. This natural rhythm of wet summers and dry dormancy is the key to successful cultivation. The bulbs thrive in humus-rich, slightly acidic to neutral soils that drain rapidly, often composed of leaf mold, eroded forest loam, limestone-derived material, or gritty alluvial deposits. In gardens, this translates to a requirement for a loose, organic, well-draining medium, often a mixture of loam, leaf mold, and grit, to prevent stagnant moisture from accumulating around the bulb. Poor drainage is the most common cause of failure, as bulbs rot readily if exposed to persistent winter wetness or heavy, airless soils.

The species grows best in part shade or dappled woodland light, though in cooler climates it may tolerate more sun. Ample fresh air movement is essential, reflecting the breezy, mountainous habitats where the species naturally occurs. During the active growing season, the soil should be kept evenly moist, particularly in late spring and summer when the plant produces rapid stem growth and forms its characteristic stoloniferous offsets. Once growth dies back in autumn, moisture should be gradually reduced and the bulbs kept relatively dry through winter. In regions with cold, wet winters, growers often achieve better results using raised beds, rock gardens, or deep containers placed under shelter to prevent winter saturation. The Royal Horticultural Society notes that the species can be grown outdoors in favorable conditions but may require container or greenhouse culture in areas with poor drainage.

Lilium nepalense can be propagated either by seed or by dividing offsets formed at the ends of stolons. Seed is epigeal and germinates readily in late spring or early summer when temperatures rise. Offset bulbs may be lifted and replanted once foliage has died back. Garden experience shows that individual accessions may differ slightly in hardiness and moisture tolerance, likely reflecting the broad ecological range of the species complex, yet all forms share the same fundamental requirements of rapid drainage, summer moisture, and a cool, relatively dry winter rest. Where these conditions are met, the species can be surprisingly vigorous, with successful cultivation reported as far north as Germany and the Pacific Northwest of the United States. Its dramatic down-facing green-and-purple flowers, combined with its exotic Himalayan origin, make Lilium nepalense a rewarding but exacting species whose cultivation success depends on an understanding of its unique monsoon-driven ecology.

Works Cited

Cotton, Arthur N. “New Species and Varieties of Lilium from Assam.” Kew Bulletin (1937).
(Original description of L. nepalense var. concolor.)

Don, David. Prodromus Florae Nepalensis: Containing Descriptions of the Plants of the Kingdom of Nepal. London: J. Gale, 1825.
(Primary description of Lilium nepalense.)

Elwes, Henry John. A Monograph of the Genus Lilium. London: Taylor and Francis, 1877–1880.
(Contains the early description of L. nepalense robustum.)

Flora of China Editorial Committee. “Lilium.” In Flora of China, vol. 24 (Flagellariaceae–Marantaceae), Science Press, Beijing & Missouri Botanical Garden Press, St. Louis, 2000.
(Distribution and taxonomy of Indochinese and Chinese Sinomartagon lilies.)

Gao, Y. D., H. T. Tran, L. Malikova, T.-W. Hsu, K.-H. Hung, et al. “Morphological and Ecological Divergence of Lilium and Nomocharis, and Its Implications for Their Evolution and Conservation.” BMC Evolutionary Biology 15 (2015): 147.
(Context on ecological divergence and Himalayan diversity.)

Gao, Y. D., et al. “Karyotype Studies in Thirty-Two Species of Lilium (Liliaceae) from Eastern Asia.” Nordic Journal of Botany 29 (2011): 184–192.
(Provides chromosomal data for Sinomartagon species, including L. nepalense.)

Gong, X., K.-H. Hung, Y.-W. Ting, T.-W. Hsu, L. Malikova, H. T. Tran, et al. “Frequent Gene Flow Blurred Taxonomic Boundaries of Sections in Lilium L. (Liliaceae).” PLOS ONE 12, no. 8 (2017): e0183209.
(Shows extensive gene flow and reticulation across Sinomartagon, supporting the species-complex interpretation.)

He, Xian. “The Population Study of Lilium nepalense.” Journal of Yunnan University (2003).
(Genetic diversity and population structure of Yunnan populations.)

Hooker, Joseph Dalton. “Lilium nepalense.” Curtis’s Botanical Magazine, plate 7170. London: L. Reeve & Co., 1889.
(Primary botanical illustration and commentary.)

Kew Herbarium Catalogue. “Lilium nepalense D. Don — Type Specimen.” Royal Botanic Gardens, Kew.
(High-resolution image of the 1821 type specimen.)

McRae, Edward. Lilies: A Guide for Growers and Collectors. Portland: Timber Press, 1998.
(Overview of ecology, cultivation, and geographic variation in Himalayan lilies.)

Nishikawa, T., K. Okazaki, T. Uchino, K. Arakawa, and T. Nagamine. “A Molecular Phylogeny of Lilium in the Internal Transcribed Spacer Region of Nuclear Ribosomal DNA.” Journal of Molecular Evolution 49 (1999): 238–249.
(One of the foundational nuclear ITS phylogenies.)

Nishikawa, T., N. Ito, and K. Okazaki. “Phylogenetic Analysis of Section Sinomartagon in Genus Lilium Using Sequences of the Internal Transcribed Spacer Region in Nuclear Ribosomal DNA.” Breeding Science 51 (2001): 39–46.
(Clarifies placement of L. nepalense relative to neighboring species.)

Pradhan, Ganesh. Field notes and photographic documentation of Lilium nepalense in Sikkim and Bhutan, 2010–2024.
(Regional morphology and variation among Himalayan populations.)

Sheriff, George. Himalayan Field Notes and Expedition Records (1930–1937). British Museum Archives.
(Distribution and abundance of L. nepalense and concolor in Bhutan.)

Wallich, Nathaniel. Plantae Asiaticae Rariores. London: Treuttel and Würtz, 1830–1832.
(Early plates and descriptions of Indomalayan lilies.)

Whitbourn, Adam. “Comparative Analysis of Himalayan and Indochinese Lilium.” Pacific Horticultural Society (2020).
(Photographic and morphological comparison of L. nepalense, majoense, primulinum, and poilanei.)

Wu, H. Z., W. W. Bai, S. L. He, Y. Zhao, and J. Z. Wu. “The Complete Chloroplast Genome of Lilium nepalense (Liliaceae).” Mitochondrial DNA Part B 6 (2021): 526–527.
(Complete plastome; confirms genetic cohesion of the species across regions.)

Yin, Guang, et al. “A Reevaluation of the Status of Lilium nepalense Based on Complete Chloroplast Genome Sequences.” American Journal of Plant Sciences 13 (2022): 473–480.
(Chloroplast phylogeny strongly supports L. nepalense as one species.)

Yunnan Flora Committee. Flora Yunnanica. Kunming: Science Press.
(Regional treatment of southern Chinese forms belonging to the nepalense complex.)