The genus Epipogium J. F. Gmelin ex Borkh., commonly known as ghost orchids, comprises terrestrial, leafless, holomycoheterotrophic herbs in the family Orchidaceae. Lacking chlorophyll, these plants entirely depend on mycorrhizal fungi for nutrition, a strategy that defines their ecological niche and explains their rarity and sporadic occurrence in natural habitats.

The species of Epipogium exhibit a highly ephemeral life cycle. Their flowering period is extremely brief, with anthesis and seed dispersal often completed within a few days. They typically inhabit shaded forest floors with moist, humus-rich soil, and their obligate reliance on mycorrhizal fungi likely contributes to their rarity and unpredictability in the wild (Satake et al., 1982; Leake, 1994; Peterson et al., 1998; The Flora of Korea Editorial Committee, 2007; Lee, 2011).

The genus comprises approximately six species worldwide, distributed from Europe across Asia (from temperate to tropical regions) south to the Malay Archipelago, the Philippines, and northeast Australia (Satake et al., 1982; The Flora of Korea Editorial Committee, 2007; Chen et al., 2009; Lee, 2011; Hsieh et al., 2018; Wu et al., 2020).

In Korea, the genus has historically been represented by a single species, E. aphyllum Sw., which is restricted to high-altitude, cool-temperate regions, including Mt. Baekdusan and the northern areas of the Korean peninsula (The Flora of Korea Editorial Committee, 2007; Sun et al., 2019). By contrast, E. roseum (D. Don) Lindl. is a widely distributed species in the Paleotropics, recorded in tropical Africa, India, Southeast Asia, China, Taiwan, and Japan (Chen et al., 2009; Kar et al., 2017; Rao et al., 2024; Zhao et al., 2024).

During a recent floristic survey on Jejudo Island, which shares a warm-temperate climate with neighboring regions, a population of Epipogium distinct from E. aphyllum was discovered in the evergreen broad-leaved forests of Seogwipo-si. A detailed morphological examination confirmed the species as E. roseum, a taxon not previously recorded in the Korean flora.

We provide a detailed description and illustrations of E. roseum based on newly collected material. In addition, we present a taxonomic key and diagnostic characters to distinguish it from the related species E. aphyllum. We also discuss the biogeographical significance of this discovery at the northernmost extent of its distribution.

Specimens of E. roseum were collected during a floristic survey in evergreen broad-leaved forests in Seogwipo-si, Jeju-do.

Morphological observations were conducted on fresh and dried materials, and diagnostic characters were compared with descriptions in relevant floras (Honda, 1997; The Flora of Korea Editorial Committee, 2007; Chen et al., 2009; Wu et al., 2020) and with specimens preserved in the herbaria of Seoul National University and Ewha Womans University. Voucher specimens have been deposited in the herbarium of Warm-temperate and Subtropical Forest Research Center, National Institute of Forest Science (WFRC). The scientific name was reviewed in the literature (Don, 1825; Lindley, 1840; Blume, 1856; POWO, 2026).

Soil samples were collected from three points around these individuals after removing the litter layer to investigate the environmental characteristics of this species’ natural habitat. Using a stainless-steel spoon, samples were taken at a depth of approximately 10–20 cm. The collected samples were combined into a composite sample, which was subsequently analyzed for physical and chemical properties, including soil texture, total nitrogen (T-N), pH, organic matter content (OM), cation exchange capacity (CEC), and electrical conductivity (EC).

Epipogium roseum (D. Don) Lindl., J. Proc. Linn. Soc. Bot. 1: 177, 1857; Limodorum roseum D. Don, Prodr. Fl. Nepal. 30, 1825; Ceratopsis rosea (D. Don) Lindl., Gen. Sp. Orchid. Pl. 384, 1840; Galera rosea (D. Don) Blume, Mus. Bot. 2: 188, 1856.

Korean name: 방울유령란(Bang-ul-eu-ryoung-ran). The proposed Korean name refers to the bell-shaped (“Bang-ul”) capsules with nodding flowers and the generic common name “ghost orchid” (“Yu-ryeong-ran”).

Diagnosis: E. roseum is a leafless, achlorophyllous mycoheterotrophic orchid, morphologically similar to E. aphyllum. However, it is readily distinguished by its tuberous, ovoid rhizome (vs. coralloid, branching rhizome in E. aphyllum), resupinate flowers with the lip facing downward (vs. non-resupinate, lip facing upward), and papillose ridges on the lip disk. Additionally, the flowering period of E. roseum on Jejudo (July) is earlier than that of E. aphyllum in northern Korea (August–September).

Herbs, terrestrial, mycoheterotrophic, 20–45 cm tall. Rhizomes tuberous, narrowly fusiform to ovoid, 2–4 cm long, 1–2 cm in diam., many-noded. Stem erect, white to cream-colored, sometimes tinged pale yellow. Leaves reduced to scalelike sheathing; sheaths 6–8, amplexicaul, white or pale yellow, 7–15 mm long, membranous. Inflorescences terminal, racemes, rachis laxly to subdensely 9–24-flowered, sometimes pendulous toward apex; floral bracts ovate-lanceolate, 6–11 × 3.5–7.5 mm. Flowers resupinate, pendulous, opening widely or not, white with faint purple spots on lip; pedicel 3–6.5 mm long; ovary 4–6 mm long; perianth segments subequal, free; sepals weakly spreading, linear-lanceolate, 8–11 × 2–3 mm, apex subacute, margin undulate, 3-veined; petals weakly spreading, often slightly shorter and wider than sepals, slightly oblique, 7–10 × 2–3 mm, apex acute to acuminate; lip ellipticovate when flattened, concave, 8–12 × 6–7 mm, spurred at base, entire, margins erose-denticulate; disk with 2 longitudinal densely papillose ridges, and occasionally with a shorter central ridge, or ridges sometimes reduced and inconspicuous; spur projecting backward, nearly parallel to ovary, cylindric, 3–5 × 1.5–2.5 mm, shorter than ovary, apex obtuse; column 2.5–4.5 mm long; anther incumbent, subglobose. Fruits capsules, broadly ovoid-ellipsoid, 5–7 × ca. 5 mm.

Flowering and fruiting: July.

Ecology: Holomycoheterotrophic, entirely dependent on symbiotic fungi for nutrition. It grows in shaded moist forest habitats, typically in wet tropical biomes.

Distribution: Tropical Africa, South and Southeast Asia, Pacific Islands: Australia, China (Guangdong, Hainan, C and S Taiwan, SE Xizang, S Yunnan), India, Indonesia, Japan, Kashmir, Laos, Malaysia, Nepal, New Guinea, Philippines, Sri Lanka, Thailand, Vietnam, and Korea (Jejudo Island).

Specimen examined: KOREA. Jeju Special Self-Governing Province: Seogwipo-si, Pyoseon-myeon, Tosan-ri, 4 Jul 2025, J. Kim 10034732 (WFRC), 7 Jul 2025, J. Kim 10034733 (WFRC), 9 Jul 2025, J. Kim 10034734 (WFRC).

To date, only one species of Epipogium has been documented in Korea, reflecting the genus’s broad yet scattered distribution across continents. With the discovery of E. roseum on Jejudo Island, Korea now hosts two species: E. aphyllum, previously recorded in northern regions, and E. roseum, newly recorded on Jejudo.

The morphological differences between E. roseum and E. aphyllum are clear, although both species are rare and easily overlooked due to their mycoheterotrophic nature. The most diagnostic feature is the rhizome structure: E. roseum possesses a tuberous, compact rhizome adapted for nutrient storage, whereas E. aphyllum has a coralloid rhizome with complex branching. Furthermore, the resupinate flowers (lip pointing down) of E. roseum contrast sharply with the non-resupinate flowers (lip pointing up) of E. aphyllum (Table 1, Fig. 1–3). These traits were consistent across all examined specimens from the Jejudo population.

This finding extends the known distribution of E. roseum northward into temperate East Asia, complements records from Japan, Taiwan, China, and Southeast Asia (Table 1), and enriches Korea’s orchid flora. It also represents the floristic and ecological uniqueness of Jejudo Island as a biodiversity hotspot.

The presence of E. roseum on Jejudo is biogeographically significant because Jejudo Island is a phytogeographical transition zone where subtropical elements persist alongside temperate flora, influenced by the Tsushima Current. Epipogium roseum is a widespread paleotropical species found in Africa, India, and Southeast Asia (Chen et al., 2009). The Jejudo population, along with those in warm-temperate Japan (Honshu and Kyushu), likely marks the northernmost extent of this species’ distribution. The discovery of E. roseum in the evergreen broad-leaved forests of Seogwipo-si further supports the island’s role as a critical refuge for subtropical plants at their northern distributional limits.

As a holomycotrophic species, E. roseum is highly sensitive to environmental changes and requires shaded, humid forest floors with rich humus and specific fungal partners to survive (Zhou et al., 2012). Soil analysis of the natural habitat of this species revealed that the soil was classified as silty loam, with an OM of 300.84 g/kg, a CEC of 61.00 cmol c/kg, a pH of 6.1, and a T-N content of 0.72%. These results indicate that the habitat is nutrient-rich, has a high capacity for nutrient uptake and retention, and poses a low risk of water stress. Given that artificial propagation is difficult, targeted conservation strategies are required for this species.

Epipogium roseum grows on very shaded forest floors. The plant community surrounding the natural habitat of the orchid includes Machilus thunbergii Siebold & Zucc., Litsea japonica (Thunb.) Juss., Neolitsea aciculata (Blume) Koidz., N. sericea (Blume) Koidz., Mallotus japonicus (L. f.) Mull. Arg., Ficus erecta Thunb., F. erect a f. sieboldii (Miq.) Miq., Ardisia crispa (Thunb.) A. DC., A. japonica (Thunb.) Blume, Oplismenus undulatifolius (Ard.) P. Beauv., Liparis kumokiri F. Maek., Hedera rhombea (Miq.) Bean, Eurya japonica Thunb., and Ampelopsis glandulosa var. heterophylla (Thunb.) Momiy.

The newly discovered population is small and localized. The species is vulnerable to habitat destruction and climate change because of its ephemeral above-ground appearance and its reliance on undisturbed forest soils. Future surveys and molecular studies are needed to clarify the distribution, genetic diversity, and ecological requirements of E. roseum in Korea. Conservation measures should be implemented to protect and monitor this rare species.