The genus Cirsium Mill. (Asteraceae) comprises approximately 498 species worldwide (POWO, 2026). It is centered in East Asia, including Korea, China, Japan, Russia, and Taiwan, but also extends to North America, Europe, and North Africa (Melchior, 1964; Dittrich, 1977; Bobrov and Czerepanov, 2001). In East Asian Cirsium, species delimitation has traditionally relied on morphological characters such as the plant habit, leaf-base shape, degree of leaf division, capitulum orientation, phyllary structure and arrangement, the presence or absence of glutinous phyllaries, the relative lengths of corolla parts, and the pappus morphology (Lamarck and De Candolle, 1805; De Candolle, 1838; Bentham and Hooker, 1873; Kitamura, 1934).

East Asian Cirsium includes many morphologically similar taxa, and variation in key characters, such as the capitulum orientation, phyllary shape and arrangement, degree of leaf division, and trichome distribution, is often continuous or overlapping, making species identification and delimitation difficult (Song and Kim, 2007; Chang et al., 2026). Recent reports of new species from China and Taiwan (Chang et al., 2019, 2021; Jin et al., 2024) together with studies of the origin, biogeography, and evolution of the genus (Moreyra et al., 2025) indicate that the taxonomy of East Asian Cirsium requires a reassessment.

To date, perennial Korean Cirsium plants with nodding capitula have generally been interpreted as C. schantarense Trautv. & C. A. Mey. in the taxonomic literature and in herbarium specimens (Chung, 1956; Park, 1974; Lee, 1980; Lee, 1996; Song, 2003; Lee, 2006; Song and Kim, 2007; Im et al., 2017; Kang, 2018). In the Korean literature, C. schantarense has been characterized by erect or adpressed phyllaries and inner phyllaries with acute to acuminate, non-expanded apices. In contrast, C. pendulum Fisch. ex DC. has been treated as a biennial taxon with nodding capitula and corolla tubes longer than the corolla limb. However, the populations from Mt. Hwaaksan and Mt. Myeongjisan in Gapyeong-gun, Gyeonggi-do, and Mt. Daeamsan in Yanggugun in Gangwon-do differ from C. schantarense in having a non-arachnoid abaxial leaf surface, bracteate capitula, and non-glutinous phyllaries, and from C. pendulum in having semi-amplexicaul leaf bases. Recently, Kim et al. (2025) referred to morphologically similar populations from Gangwon-do and Gyeonggi-do as C. diamantiacum (Nakai) Nakai. However, the phyllaries, corolla, and pappus proportions observed in the original description and type material of C. diamantiacum do not correspond to those of the populations examined in the present study. We therefore conducted a comprehensive study of the morphology, protologues, and type specimens to clarify the taxonomic identity of these populations. As a result of this effort, we describe them here as a new species.

Dried and spirit specimens were prepared from plants collected during the flowering and fruiting seasons on Mt. Hwaaksan, Gapyeong-gun, Gyeonggi-do, Korea. Samples from selected plant organs were dissected and preserved in 70% ethanol for morphological observation. The comparative taxa selected were C. schantarense, C. pendulum, and C. diamantiacum, which are morphologically similar to the new species and have either been confused with it in identification or have been recently recognized by Kim et al. (2025). The original descriptions of these taxa were examined and compared. In addition, the syntype of C. schantarense (LE), the syntype of C. pendulum (G), and the holotype of C. diamantiacum (TI) were examined.

To assess additional morphological variations, specimens or high-resolution images from various herbaria (ANH, B, HLUA, IFP, JLSLKY, KB, KH, KNKA, KNU, KUN, KWUA, LE, MNHMP, MW, MWG, NEAU, PE, RSA, SNUA, TI, and VMVT) were examined, and some specimens were loaned to facilitate direct observations (Appendix 1). In addition, the photographs of C. diamantiacum shown in Figs. 1 and 2 were provided by TI and were used for morphological measurements. Measurements were taken from photographs only when scale bars or directly comparable structures were available.

Morphological observations were based on dried specimens, spirit specimens, and living materials collected during the flowering and fruiting seasons. The qualitative and quantitative characters of vegetative and reproductive organs were observed and measured using a vernier caliper (Brutsch/Ruegger Tools Ltd., Urdorf, Switzerland), and major diagnostic characters were photographed with a stereomicroscope (Olympus AX-70, Tokyo, Japan; IMTcamUSB3.0_ISP6.3, Canada).

Cirsium reflexiphyllarium S. H. Kim & G. Y. Chung, sp. nov. —TYPE: KOREA. Gyeonggi-do: Gapyeong-gun, Bukmyeon, Mt. Hwaaksan, 37°59′55.93″N, 127°30′38.58″E, elev. 1,214 m, 26 Jul 2024 [fl], S.H. Kim & G.Y. Chung KSH20240726-001 (holotype: ANH; isotypes: ANH [2 sheets], KH) (Figs. 3, 4).

Korean name: Ban-gok-eong-geong-kwi (반곡엉겅퀴).

Diagnosis: Cirsium reflexiphyllarium is most similar to C. schantarense and C. diamantiacum in having nodding capitula and semi-amplexicaul leaf bases. It differs from C. schantarense in having a non-arachnoid abaxial leaf surface; bracteate capitula; reflexed, non-glutinous phyllaries; and a linear pappus apex; and from C. diamantiacum in the relative proportions of the phyllaries, corolla, and pappus (Fig. 2, Table 1).

Herbs perennial, 77–182 cm tall. Roots numerous, fibrous. Stems erect, sulcate, branched or unbranched, green to reddish brown, densely pubescent. Radical and lower cauline leaves withering at flowering, alternate, petiolate; petioles 6.7–23.3 cm long, with densely spinulose margins; blades 25–42 × 20–24 cm, obovate, pinnately parted or divided, both surfaces green, adaxial surface sparsely papillate, abaxial surface non-arachnoid, veins shortly pubescent; lobes 7–17, irregularly triangular, apex acute, margin spinulose-ciliate, spines 1–4 mm long. Middle cauline leaves alternate, pinnately lobed or cleft, sessile, base auriculate, semi-amplexicaul; blades 10–33 × 5–22 cm, ovate to ovate-lanceolate, both surfaces green, abaxial surface non-arachnoid, veins shortly pubescent; lobes 9–13, irregularly triangular, apex acute, margin spinulose-ciliate, spines 1–4 mm long. Upper cauline leaves similar to middle cauline leaves but gradually smaller. Capitula nodding, solitary at the apex of the stem or branches, bracteate; peduncles 6.3–14.7 cm long, dark green; bracts 6.8–10.4 mm long, lanceolate, with spinose margins. Involucres 3.5–4.0 cm wide, campanulate, green to dark purple. Phyllaries in 6–7 series, 9–13 × 0.7–1.8 mm, each with a linear glandular dorsal ridge, not glutinous; outer and inner phyllaries nearly equal in length; outer phyllaries ovate-lanceolate to lanceolate, gradually reflexed, sometimes spreading horizontally; middle phyllaries ovate-lanceolate to lanceolate, reflexed; inner phyllaries lanceolate, membranous, apex reflexed, spinulose. Corollas 15.5–17.5 mm long, tubular, 5-lobed, purple to pale purple; tubes 4.5–5.0 mm long, with limbs ca. 2.5 times as long as the tubes; stamens 5; anthers syngenesious, yellow; filaments brown to dark brown, pubescent; style dark brown to black, strongly exserted from the corolla. Achenes 3.2–4.5 × 1.4–1.8 mm, narrowly elliptic, 4-angled and longitudinally ribbed, brown to light brown. Pappus 2-seriate, 14–15 mm long, ca. 3 times as long as the corolla tube, plumose, white to pale yellow, apex linear.

Etymology: The specific epithet refers to the reflexed phyllaries.

Phenology: Flowering from July to September; fruiting from September to October.

Distribution and ecology: Mt. Hwaaksan in Gapyeonggun, Gyeonggi-do, and Hwacheon-gun, Gangwon-do; Mt. Myeongjisan in Gapyeong-gun, Gyeonggi-do; and Mt. Daeamsan in Inje-gun and Yanggu-gun, Gangwon-do, Korea (Fig. 5). This species inhabits moist, open areas at elevations of 1,000–1,400 m.

Taxonomic note: Cirsium reflexiphyllarium has most often been confused with C. schantarense in floras, the taxonomic literature, and during herbarium specimen identification owing to its nodding capitula. It differs from C. schantarense in having a non-arachnoid abaxial leaf surface; bracteate capitula; reflexed, non-glutinous phyllaries; and a linear pappus apex. In contrast, C. schantarense has a densely arachnoid abaxial leaf surface, ebracteate capitula, adpressed and glutinous phyllaries, and a clavate pappus apex (Figs. 1D, 2D, Table 1).

Recently, Kim et al. (2025) referred to the present species as C. diamantiacum on the basis of the incised margins of the middle and upper cauline leaves and proposed the Korean name ‘Geum-gang-san-eong-geong-kwi’. However, examinations of the protologue and type material of C. diamantiacum showed that its inner phyllaries are approximately twice as long as the outer phyllaries, the corolla limb is approximately twice as long as the corolla tube, and the pappus is nearly equal in length to the corolla tube. In C. reflexiphyllarium, in contrast, the inner and outer phyllaries are nearly equal in length, the corolla limb is approximately 2.5 times as long as the corolla tube, and the pappus is approximately three times as long as the corolla tube (Figs. 1C, 2C, Table 1). These differences clearly distinguish the present species from C. diamantiacum (Figs. 1A, 2A, Table 1). Although C. diamantiacum has often been treated as a synonym of C. schantarense in the literature, it is treated here as a distinct taxonomic concept for comparative purposes because its protologue and type material indicate a morphology different from both C. schantarense and the present species. Accordingly, the application of the Korean name ‘Geum-gangsan-eong-geong-kwi’ to the Hwaaksan–Myeongjisan–Daeamsan populations is not appropriate. Cirsium pendulum resembles the new species in having nodding capitula and reflexed phyllaries. However, C. pendulum differs from the new species in having non-amplexicaul leaf bases, phyllaries arranged in eight series, filiform florets, and a corolla tube approximately 2.5 times as long as the corolla limb (Figs. 1B, 2B, Table 1). These combined morphological characters support the recognition of the populations from Mt. Hwaaksan, Mt. Myeongjisan, and Mt. Daeamsan as a distinct species, here described as Cirsium reflexiphyllarium. The Korean name ‘Ban-gok-eong-geong-kwi’ is proposed for this species.

Cirsium pendulum is widely distributed in Russia, China, Mongolia, Japan, and Korea and is clearly distinguished from C. reflexiphyllarium by its external morphology. Therefore, no direct taxonomic confusion has arisen between these two species. In the present study, the distributions of C. schantarense and C. diamantiacum, which have been taxonomically confused with C. reflexiphyllarium, are mapped, as shown in Fig. 5. C. diamantiacum was confirmed only from specimens collected on Mt. Geumgangsan in North Korea. Although C. schantarense has been treated in Korean literature as a taxon occurring mainly in the northern mountainous regions of the Korean Peninsula, the specimens examined in this study indicate that C. schantarense is distributed in northeastern China and the Russian Far East. On the other hand, C. reflexiphyllarium is currently known only from deep mountain habitats in Gapyeong-gun, Gyeonggi-do, and Hwacheon-gun, Inje-gun, and Yanggu-gun, Gangwon-do, Korea, indicating a highly restricted distribution.

Specimens examined (paratypes): KOREA. Gyeonggi-do: Gapyeong-gun, Buk-myeon, Mt. Hwaaksan, 26 Jul 2024, S.H. Kim & G.Y. Chung KSH20240726-005–012 (ANH); 19 Aug 2024, S.H. Kim & G.Y. Chung KSH20240819-001, 002 (ANH); 25 Jul 2025, S.H. Kim & G.Y. Chung KSH20250725-001–008 (ANH); Gapyeong-gun, Buk-myeon, Mt. Hwaaksan, 18 Jul 1998, Y.D. Kim et al. 11680 (KB); 30 Sep 2010, E.S. Jeon ESJeon102694 (KH); 12 Sep 2018, J.D. Lee et al. 18370-1/2 (KB); 17 Aug 2011, E.S. Jeon 2011018 (KH); Mt. Myeongjisan, 12 Jul 1997, S.S. Kim & Y.M. Lee s.n. (KH); 11 Aug 2011, C.H. Kim 11209 (KH). Gangwon-do: Hwacheon-gun, Sanae-myeon, Mt. Hwaaksan, 30 Jul 2008, E.S. Jeon ESJeon80553 (KH); Inje-gun, Seohwa-myeon, Mt. Daeamsan, 31 Jul 2009, H.T. Im Im1401 (KB); Yanggu-gun, Dong-myeon, Mt. Daeamsan, 4 Jul 2000, C.S. Chang 0023066, 00042066 (SNUA); 21 Jun 2000, K.Ch. Yang et al. EN2000AJOU737, 738 (KB); 10 Jul 2003, E.S. Jeon ESJeon31016 (KH).