Rosa maximowicziana Regel (Rosaceae) is a wild rose species native to the Korean Peninsula, occurring in North Korea and its neighboring regions globally (Chang et al., 2011; Choi, 2017a). This wild rose is named after Carl Johann Maximovich (1827–1891), a Russian botanist who first officially collected this species in southeastern Manchuria near Posyet (Primorsky Krai, Russia) in 1860, during his second journey to East Asia (1859–1864) (Regel, 1878; Rix, 2020). With its exserted and agglutinated styles, R. maximowicziana is classified as the section Synstylae, which includes two other wild rose species native to Korea: Rosa lucieae Franch. & Rochebr. ex Crép. and R. multiflora Thunb. Despite its early recognition on the Korean Peninsula by pioneering taxonomists, such as Takenoshin Nakai and Tai Hyun Chung, R. maximowicziana has been poorly understood in South Korea, with only few records after Chung’s collections. Furthermore, R. lucieae has often been misidentified as R. maximowicziana in Korea due to their similar vernacular names (R. maximowicziana: 용가시나무[yong-ga-si-na-mu]; R. lucieae: 돌가시나무[dol-ga-si-na-mu]), while R. multiflora has also been confused with R. maximowicziana due to their morphological similarities. Although several recent Korean taxonomic investigations recognized the distinctiveness of R. maximowicziana and distinguished this from its close relatives (i.e., R. lucieae and R. multiflora) (Chang et al., 2011; Choi, 2017a; Kim, 2022), its morphology, ecology, and biogeography remain insufficiently documented and poorly understood.

One of the most well-known characteristics of R. maximowicziana is its geographic confinement to North Korea and its adjacent areas (Chang et al., 2011; Choi, 2017a; Kim, 2022). These regions lie along the boundary between temperate and hemiboreal forests, whereas most wild roses in the section Synstylae inhabit subtropical to temperate forests (Rehder, 1940). A recent genome-wide molecular phylogenetic study elucidated the distinct and robust species lineage of R. maximowicziana, underscoring its unique evolutionary history in hemiboreal ecosystems (Jeon et al., 2025a). Unfortunately, highly fragmented and sparse populations in South Korea are extremely vulnerable due to recent global climate change, which may significantly affect habitat loss. Consequently, a comprehensive understanding of R. maximowicziana is pivotal for its conservation in South Korea. However, due to limited ecological and taxonomic information, the conservation importance of R. maximowicziana has been overlooked in South Korea, only with its categorization as Data Deficient (DD) on the National Red List in Korea assessed by Korea National Arboretum (2021).

Here, we revisited R. maximowicziana in South Korea based on extensive herbarium research and 12 years of field investigations, focusing on its distribution, morphology, phenology, habitat preferences, and population structure. Additionally, we compiled updated records of South Korean populations, and identified potential and ongoing threats for the persistence of this species in South Korea. Through this integrative approach, we aim to underscore the conservation significance of R. maximowicziana in South Korea.

To understand the distribution of R. maximowicziana in South Korea and adjacent countries, we examined herbarium specimens deposited in the various herbaria around the world, including the Ha Eun Herbarium of Sungkyunkwan University (SKK), the herbaria of the Korea National Arboretum (KH) and the National Institute of Biological Resources (KB), as well as several virtual herbaria: the Harvard University Herbaria & Libraries (https://kiki.huh.harvard.edu), Royal Botanic Gardens, Kew (https://data.kew.org), French National Museum of Natural History (https://science.mnhn.fr), Korea National Arboretum (https://nature.go.kr), Chinese Virtual Herbarium (https://cvh.ac.cn), Moscow Digital Herbarium (https://plant.depo.msu.ru), and Herbarium of the University of Tokyo (https://umdb.um.u-tokyo.ac.jp/DShokubu) (Appendix 1). Specimen information collected from North Korea was retrieved from a checklist compiled by Chang et al. (2020). For collections from the early 20th century on the Korean Peninsula, historical locality names were identified using a botanical gazetteer and a bibliography compiled by Chang et al. (2015, 2016).

We explored wild populations of R. maximowicziana in South Korea through a total of 31 field investigations from 2014 to 2025, aiming to understand the geographical distribution, habitat environment, morphology, phenology, and population ecology of R. maximowicziana. Based on the localities of the examined herbarium specimens, our investigations focused on the northern and northwestern regions of South Korea, encompassing Seoul, Incheon, northern Gangwon (Cheorwon, Goseong, Hwacheon, and Yanggu), northern Gyeonggi-do (Dongducheon, Paju, Pocheon, Yangju, and Yeoncheon), and western Gyeonggi-do (Ansan and Hwaseong), which are adjacent to North Korea by land or sea (Appendix 2). Because R. maximowicziana has not been collected or observed in the southern regions of South Korea for over a century, even if contemporary individuals observed there by any chance, they should be regarded as vagrants or visitors and thus not included in conservation assessments (International Union for Conservation of Nature, 2012a). Observed populations were defined as geographically distinct groups, separated by a physical distance over 3 km.

Morphological traits of R. maximowicziana were observed and measured in up to ten mature individuals per population, with putative hybrids excluded to ensure morphological integrity. Voucher specimens collected from each population in South Korea were deposited in the herbarium SKK (Appendix 1). Metapopulations were demarcated based on a minimum physical distance over 15 km between the nearest populations. Area of occupancy (AOO) was calculated using a 2 × 2 km grid cells, and extent of occurrence (EOO) was measured by a minimum convex polygon, following the International Union for Conservation of Nature (IUCN) guidelines (International Union for Conservation of Nature, 2012b).

Through the examination of specimens and field investigations throughout 12 years, we assessed a total of 22 previously known and newly identified populations of R. maximowicziana in South Korea (Table 1), and compiled an illustrated description of R. maximowicziana, including its morphology (Fig. 1), geographical distribution (Fig. 2), and population ecology (Table 1).

Rosa maximowicziana Regel, Trudy Imp. S.-Peterburgsk. Bot. Sada 5: 378, 1878.—TYPE: RUSSIA. Possjes, Mandshuria austra-orientalis. Maximowicz. iter secundum, 1860, C. J. Maximowicz s.n. (types: K000730850, P03204404, Photo!; LE?).

Rosa lucieae var. aculeatissima Crép. ex Regel, Trudy Imp. S.-Peterburgsk. Bot. Sada 5: 378, 1878 (type: LE?).

Rosa coreana R. Keller, Bot. Jahrb. Syst. 44: 46, 1909; Rosa granulosa var. coreana (R. Keller) Nakai, Fl. Quelpaert Isl.: 53, 1914; Rosa maximowicziana var. coreana (R. Keller) Kitag., Neolin. Fl. Manshur.: 383, 1979.—TYPE: KOREA. in Kan-ouen-to, communis, Jul 1901, U. Faurie 98 (types: P03204764, P03204765, Photo!).

Rosa jackii Rehder, Mitt. Deutsch. Dendrol. Ges. 19: 251, 1910; Rosa maximowicziana var. jackii (Rehder) Rehder, J. Arnold Arbor. 3: 209, 1922.—TYPE: KOREA. Seoul, J. G. Jack 1905, Cultivated at the Arnold Arboretum, Jamaica Plain, 1 Jul 1909, A. Rehder s.n. (types: A00032588, A00032589, Photo!).

Rosa kelleri Baker ex E.Willm., Rosa 1: 75, 1911, nom. illeg.

Rosa spinosissima var. mandshurica Y.Yabe, Enum. Pl. S. Manchuria: 70, 1912.

Rosa maximowicziana f. adenocalyx Nakai, Bot. Mag. (Tokyo) 30: 235, 1916; Rosa maximowicziana var. adenocalyx (Nakai) Nakai, Bull. Natl. Sci. Mus. Tokyo 31: 58, 1952.—TYPE: KOREA. “平安北道 義州,” 3 Jun 1914, T. Nakai 1818 (lectotype: TI00022353, Photo!; syntypes: TI00022349, TI00022350, TI00022351, TI00022352, Photo!).

Rosa maximowicziana f. leiocalyx Nakai, Bot. Mag. (Tokyo) 30: 235, 1916.—TYPE: KOREA. “咸鏡道 摩天嶺”, Jul 1902, A. Mishima s.n. (lectotype: TI00022348, Photo!).

Korean name: 용가시나무 (Yong-ga-si-na-mu).

Chinese name: 伞花蔷薇 (San-hua-qiang-wei).

Russian name: Шиповник Максимовича (Shipovnik Maksimovicha).

English name: Maximowicz’s rose.

Shrubs deciduous, rambling. Stems decumbent, grayish brown to reddish brown; branchlets terete, yellowish green to reddish brown; prickles thin, slightly curved, usually dense to scattered, sometimes paired at nodes. Leaves alternate, imparipinnate, 7.8–13.4 cm long, 3.5–8.8 cm wide; stipules narrow, rarely wide, mostly adnate to petioles, 1.2–2.2 cm long, margins glandular-serrate or glandular-dentate, auricles narrowly lanceolate; rachis sparsely pubescent, abaxially armed with short prickles; leaflets (5–)7–9, adaxially green to deep green, abaxially pale green, elliptic, sometimes obovate, lanceolate, or oblong, 2.4–5.0 cm long, 1.0–2.3 cm wide, glabrous, lustrous, abaxially sparsely pubescent along the midrib, base cuneate or oblique, rarely round, margin serrate or dentate, apex acute or acuminate. Inflorescences cymose corymbs with 2–9(–15) flowers or solitary. Flowers complete, bisexual, actinomorphic, 3.0–5.5 cm in diameter; pedicel 1.5–4.1 cm long, glandular-pubescent or glabrous; bracts ovate or lanceolate, margin glandular-serrate; hypanthium ovoid or globose, glabrous, rarely glandular; sepals 5, deciduous, light green to green, triangular-ovate or triangular-lanceolate, 1.1–2.2 cm long, adaxially pubescent to tomentose, abaxially glandular-pubescent, margin entire or 1- to 2-lobed, apex caudate or long acuminate; petals 5, white, sometimes tinted with yellow, fragrant, obovate, base cuneate, apex emarginate, retuse, or obcordate; stamens numerous; styles exserted, agglutinated into column, glabrous. Fruits hips, bearing several achenes, orange to red, ovoid or globose, 8.7–12.9 mm long, 7.6–11.2 mm wide, glabrous, rarely glandular.

Flowering: Late May to June.

Fruiting: September to October.

Distribution: Seoul (Gwanak-gu), Incheon (Ganghwa-gun, Ongjin-gun), Gangwon (Cheorwon-gun, Goseong-gun, Hwacheon-gun), Gyeonggi-do (Ansan-si, Dongducheon-si, Hwaseong-si, Pocheon-si, Yangju-si, Yeoncheon-gun) [North Korea, China (Hebei, Jilin, Liaoning), Russia (Primorsky Krai)].

Habitat: Forest edges, thickets, and meadows with wet soils; swamp forest; riverbanks.

Elevation: 0–500m a.s.l.

Diagnosis: Due to their close relationships, R. maximowicziana and its Korean relatives, R. lucieae and R. multiflora, share some common characteristics. Among them, R. maximowicziana can be distinguished by its stems with dense to scattered thin prickles, larger flowers with longer pedicels forming cymose corymbs, and longer sepals with caudate or long-acuminate apices (Choi, 2017b; Chung, 2017) (Fig. 3, Table 2). Compared with R. multiflora, R. maximowicziana has stipules with glandular-serrate margins, lustrous leaf surface, generally seven or nine elliptic leaflets per leaf, larger flowers (3.0–5.5 cm in diam.) in cymose corymbs, and larger hips (8.7–12.9 cm long, 7.6–11.2 mm wide), whereas R. multiflora has stipules with pectinate margins, non-lustrous leaf surface, generally five to seven obovate leaflets per leaf, smaller flowers (1.5–4.0 cm in diam.) in cymose panicles, and smaller hips (5.2–7.8 mm long, 4.3–7.3 mm wide) (Chung, 2017). Additionally, we observed that R. multiflora generally blooms two to three weeks earlier (May) than R. maximowicziana (Late May to June) in the same locations. Compared with R. lucieae, R. maximowicziana has thinner and longer leaflets (2.4–5.0 cm long), longer pedicels (1.5–4.1 cm long), and glabrous styles, whereas R. lucieae has coriaceous and shorter leaflets (0.5–2.5 cm long), shorter pedicels (0.5–1.5 cm long), and pubescent to tomentose styles (Choi, 2017b). Most evidently, they differ in geographical distribution: R. maximowicziana inhabits temperate or hemiboreal forests above the 37th parallel north, whereas R. lucieae inhabits subtropical forests below the 37th parallel north.

Taxonomic Notes: Decumbent stems of well-established R. maximowicziana sometimes develop roots and anchor to the ground, enabling asexual reproduction through clones (ramets), thus forming clonal colonies (genets). A morphological variation along its geographic distribution was observed in the pedicel surface: pedicels of nearly all South Korean individuals were densely glandular-pubescent, whereas those of Chinese and Russian individuals were often glabrous or sparsely glandular-pubescent. Rosa maximowicziana easily outcrosses with R. multiflora in South Korea due to their sympatry. Despite prezygotic reproductive isolation via phenological differences (i.e., later flowering of R. maximowicziana), overlapping flowering times sometimes lead to hybridization. Hybrid offsprings may exhibit intermediate morphological traits between the parental species (e.g., partially pectinate stipule margins and scattered thick and curved prickles), or mosaic traits (e.g., stems with dense thin prickles like R. maximowicziana, but stipules with pectinate margins and small flowers in cymose panicles like R. multiflora) (Fig. 3A–R). An interesting finding was that some hybrids had weakly agglutinated styles, which became free after floral senescence. Therefore, botanists and other researchers should exercise caution when recognizing R. maximowicziana in South Korea, ensuring that hybrid characteristics are not mistaken for species-defining traits. Generally, Rosa diversistyla Cardot, R. jackii var. pilosa Nakai, R. jaluana Kom., R. nakaiana H.Lév., and R. pimpinellifolia var. coreana (Kom.) Boulenger have been considered synonyms of R. maximowicziana. However, R. jackii var. pilosa and R. nakaiana should be regarded as synonyms of R. multiflora, based on paired thick prickles, pectinate stipules, obovate leaflets, and numerous flowers in panicles, according to their protologues (Léveillé, 1912; Nakai, 1916) and type specimens (R. jackii var. pilosa—TYPE: KOREA, 水原農林學校見學園, 31 May 1912, H. Ueki 138. holotype: TI00022355, Photo!; R. nakaiana—TYPE: KOREA, in Coreâ mediâ, Jul 1906, U. Faurie 330. isotype: TI00022347, Photo!). On the other hand, we obviously identify R. jaluana as a different species from R. maximowicziana in other section but Synstylae, based on wider stipules with ovate auricles, membranous leaves, longer sepals, purple corolla, and pubescent, non-exserted styles, according to its protologue (Komarov, 1904) and holotype specimen (TYPE: KOREA, Flumen Amnok-gan, septentrionalis provincial Pen-nian, 27 Jun 1897, V. L. Komarov s.n. holotype: LE01001986, Photo!). Komarov (1904) also noted that R. jaluana is close to Rosa macrophylla Lindl. in the section Rosa in the protologue. Rosa pimpinellifolia var. coreana has been misinterpreted as a homotypic synonym of R. coreana R.Keller, which is one of the heterotypic synonyms of R. maximowicziana. However, this name was explicitly described as a homotypic synonym of Rosa koreana Kom. in its protologue (Boulenger, 1936), referring to a different species from R. coreana. Its type specimen was also collected as R. koreana by E. H. Wilson in 1917 (TYPE: KOREA, Prov. N. Kankyo, 24 Aug 1917, E. H. Wilson 9008. type: K004277105, Photo!). Rosa diversistyla appears to be a natural hybrid between R. lucieae and R. multiflora, based on its collection locality (Jeju Island, Korea), morphological traits being intermediate between the two species, and its free styles (Cardot, 1917; TYPE: KOREA. in sepibus Quelpaert, Jun 1907, U. Faurie 1569. type: P03204157, Photo!). Similarly, the free styles of Rosa taisensis Nakai also suggest a hybrid origin, possibly between R. maximowicziana and R. multiflora (Nakai, 1943; TYPE: KOREA, 黃海道長淵郡大靑島, 14 Jun 1924, T. H. Chung s.n. holotype: TI00022339, Photo!).

Through our investigations, populations of R. maximowicziana were found in forests and thickets with wet soils, marsh meadows, swamp forests, riverbanks, or coastal lowlands above the 37th parallel north, near the border with North Korea. This finding suggests that R. maximowicziana inhabits cool temperate forests with sufficient water storage and sunlight, conditions that are uncommon and limited in South Korea due to its complex topography with numerous mountains. Furthermore, as these habitats are disconnected and sparsely scattered in small patches across northern South Korea, the distribution of R. maximowicziana is clumped within highly restricted areas in South Korea, with only eight metapopulations identified (Fig. 2, Table 3). Except for the metapopulations in Ongjin and Goseong, which are presumed to be more closely related to North Korean populations (Fig. 2), physical distances between metapopulations ranged from 17.2 to 58.3 km (30.3 km on average). Additionally, the average distance between populations within each metapopulation was 7.4 km, supporting a severe level of population fragmentation for R. maximowicziana in South Korea. Despite their proximity to North Korea and the presence of abundant wetlands, no stable populations of R. maximowicziana were found in Ganghwa, Gimpo, or Paju (Appendix 2). Conversely, despite considerable distances from North Korea, R. maximowicziana populations were found in wetland forests or thickets in Mt. Bukhansan, Mt. Gwanaksan, Ansan, and Hwaseong (Fig. 2, Tables 1, 3), and they have been consistently observed over several decades (Appendix 1). These patterns and long-term records suggest that R. maximowicziana is not a vagrant taxon confined to the North Korean border, but a robust native taxon in South Korea but with highly restricted distribution ranges.

In addition to its restricted distribution, most South Korean populations of R. maximowicziana are highly threatened and susceptible to extirpation, consisting of few individuals or genets (populations BHS, GNK, IDM, JGE, JGM, MSS, NYE, SMD, SNM, SSM, SYS, and TSM; see Table 1). Unfortunately, the extermination of population GNK (the only population found in Mt. Gwanaksan, Seoul) was observed during an investigation in 2025, indicating the possible local extinction of R. maximowicziana in Mt. Gwanaksan (Table 4). Furthermore, the reduction of suitable habitats due to global climate change, deforestation, and urbanization is inducing declines in both number and size of populations of R. maximowicziana. Most populations were found next to roads, trails, rice paddies, or crop fields, where frequent and repeated clearing threatens their sustainability and viability. For example, although population CBS (Mt. Chilbosan, Gyeonggi-do) is one of the most stable populations in South Korea and lies within the species’ southernmost range globally, a decline in its size due to clearing was observed during an investigation in 2025 (Table 4).

Additionally, low genetic diversity, frequent outcrossing, and competition with R. multiflora are other major drivers accelerating the reduction of population sustainability of R. maximowicziana in South Korea. Due to self-incompatibility of wild rose species (Ueda and Akimoto, 2001), high genetic diversity is essential for long-term viability of a rose species. Nonetheless, asexual reproduction, small population sizes, and limited suitable habitats have led to reduced genetic diversity of R. maximowicziana populations in South Korea. Moreover, R. maximowicziana frequently outcrosses with closely related, widespread, and rampant R. multiflora (Jeon et al., 2025b), leading to reproductive failure and generation of hybrid offsprings. In addition to its high fecundity based on many-flowered panicle-like inflorescence, R. multiflora thrives in most thickets, forest edges, and riverbanks across temperate forests in South Korea, regardless of soil moisture conditions. The larger population size and greater viability of R. multiflora reduce the occurrence of R. maximowicziana through competitive exclusion. Furthermore, recurrent introgressive hybridization threatens the genetic integrity of South Korean R. maximowicziana via genetic swamping, the overwhelming introgression of genetic material from common R. multiflora into the rare R. maximowicziana. Among investigated populations, populations GNK, JGM, SSM, and TSM consisted entirely of hybrids between R. maximowicziana and R. multiflora, indicating an extremely severe threat from introgressive hybridization (Table 1). Despite the largest population size of population BND (Baengnyeongdo Island, Incheon), nearly all individuals exhibited one or more traits of R. multiflora (e.g., thick and curved prickles, pectinate stipule margins, non-lustrous leaf surface, small flower size, and early flowering), implying a high level of introgressive hybridization within this population. This extensive hybridization has made it impracticable to demarcate the boundaries between R. maximowicziana and R. multiflora in this population. The formation of a hybrid swarm on Baengnyeongdo Island may be closely related to reproductive isolation with other populations, caused by separation by the Yellow Sea. Considering the high fecundity of R. multiflora, the exceptional population size of this hybrid swarm may have originated from introduced traits of R. multiflora (Table 1).

Taken together, Cheorwon would be the only stable region where R. maximowicziana persists in South Korea, with sufficient number of populations, sustainable population sizes, and low levels of introgressive hybridization, based on its landscape ecological characteristics. Cheorwon is a volcanic basin with the Hantangang River and abundant wetlands (Kim, 2013), which provides widespread suitable habitats for R. maximowicziana. To the southwest of Cheorwon, marginal populations were found downstream of the Hantangang River, across Yangju, Dongducheon, and Yeoncheon, occupying several suboptimal habitats. Mt. Chilbosan and the lowlands of Hwaseong represent the southernmost regions for marginal populations, where wetlands are particularly well developed (Lee, 2019; Moores et al., 2022). Outside these three regions, South Korean populations of R. maximowicziana were highly unstable and susceptible to extirpation, due to extremely small population sizes, severe fragmentation, introgressive hybridization, and ongoing anthropogenic threats.

Consequently, urgent conservation strategies and action plans for R. maximowicziana are required in South Korea, considering its fragmented distribution, restricted habitat, habitat destruction, small population size, low genetic diversity, and severe introgressive hybridization. To better clarify its conservation significance, we applied the criteria for the IUCN Red List (International Union for Conservation of Nature, 2012b) to R. maximowicziana in South Korea. For criterion B (Geographic range), AOO of R. maximowicziana in South Korea was calculated at 136 km² (Table 3); the geographic range is severely fragmented into eight metapopulations, of which three are hybrid swarms or extirpated (Goseong, Mt. Gwanaksan, and Ongjin) (Tables 1, 3); and ongoing declines in numbers of locations, populations, and mature individuals were observed (Tables 1, 4). Based on these observations, R. maximowicziana would be possibly categorized as Endangered (EN; B2ab(iv,v)) in South Korea. For criteria C (Small population size and decline) and D (Very small or restricted population), this species would be possibly recognized as Critically Endangered (CR; C2a(i)) or EN (D), considering its markedly low number of mature individuals or genets (75 in total; 4.4 per population on average) with ongoing population decline (Table 4). According to the IUCN guidelines for Regional or National Red List (International Union for Conservation of Nature, 2012a), a taxon cannot be assessed if less than 1% of its global population occurs in the region. Despite its limited distribution, EOO of R. maximowicziana in South Korea was measured at 20,597.4 km², representing 4.6% of its global EOO (445,381.7 km²), supporting the applicability of IUCN Red List criterion. Given South Korea’s proximity to North Korea, where the majority of global R. maximowicziana populations occurs (Fig. 2), a rescue effect through immigration from North Korea could potentially lower the Red List category to EN or Vulnerable (VU) (Gärdenfors et al., 2001). However, considering severe deforestation in North Korea (Jin et al., 2023), poleward range shifts of plants in cool temperate and boreal forests due to global warming (Boisvert-Marsh et al., 2014; Ramalho et al., 2023), and rapid environmental changes in wetland ecosystems caused by urbanization and global climate change (Salimi et al., 2021; Xiong et al., 2023), a rescue effect of R. maximowicziana in South Korea would be marginal and implausible. The lack of information on North Korean populations may hamper future assessments of R. maximowicziana as a regionally threatened species in South Korea. Nevertheless, we would like to underscore the urgent necessity for a Regional Red List assessment of R. maximowicziana in South Korea, along with appropriate conservation planning, population monitoring, and habitat management. Our efforts to conserve R. maximowicziana and its habitats will contribute to the sustained biodiversity of the Korean Peninsula, and advance our understanding of conservation approaches for plant species occurring in cool temperate forests and wetland ecosystems.