Plantaginaceae, the plantain family, is a family of flowering plants in the order Lamiales (Xu and Chang, 2017). The expanded Plantaginaceae family, which includes many taxa formerly placed in the Scrophulariaceae family, contains approximately 100 genera and over 2000 species. The family has a cosmopolitan distribution but occurs particularly in temperate regions (Albach et al., 2005; Xu and Chang, 2017; POWO, 2024). The genus Plantago L. comprises approximately 300 species and is one of the major genera of Plantaginaceae. These plants are small annual or perennial herbs with elliptic leaves and spikes bearing tiny flowers (Gonçalves and Romano, 2016).

The word Plantago is taken from the Latin word “planta,” which means “sole of the foot” (Pandita, 2013). The genus name refers to the broad leaves resembling the soles of the feet, which are spread low to the ground. For centuries, Plantago species have been used in traditional medicine to treat diseases such as constipation, hyperlipidemia, hyperglycemia, hypertension, cough, and wounds (Najafian et al., 2018; Ji et al., 2019). The mucilaginous product (psyllium) isolated from seed husks is widely used in the food industry in products such as Metamucil and Mucilin, which have been reported in several clinical studies to increase satiety, maintain blood glucose levels, lower cholesterol levels, and exert laxative effects (Guo et al., 2008; Brum et al., 2016; Lertpipopmetha et al., 2019; Zhang et al., 2021). Recent pharmacological and phytochemical studies have shown that polysaccharides isolated from Plantago spp. have multiple medicinal and nutritional benefits, including improved intestinal health and hypoglycemic effects (Zhang et al., 2021). For example, P. major L. (great plantain), which is distributed worldwide, contains several effective chemical constituents, among which polysaccharides are the most abundant, exhibiting antiulcerative, antidiabetic, antidiarrheal, anti-inflammatory, antinociceptive, antibacterial, and antiviral properties (Adom et al., 2017; Lukova et al., 2017).

Rahn (1996) divided the genus Plantago into six subgenera based on morphology (Rahn, 1996). Infrageneric classifications have also been established based on chemical markers using iridoid glucosides and based on molecular data using restriction endonuclease site variability (Andrzejewska-Golec, 1992; Wolff and Schaal, 1992; Rønsted et al., 2000). Recently, Rønsted et al. (2002) defined five subgenera [Plantago, Coronopus (Lam. & DC.) Rahn, Psyllium (Juss.) Harms & Reiche, Bougueria (Decne) Rahn, and Littorella (P. J. Bergius) Rahn] for the classification of Plantago based on molecular studies using nuclear ribosomal internal transcribed spacer and plastid trnL-F sequence data.

To date, ten Plantago taxa have been reported on the Korean Peninsula. Among these, seven native plants belong to subg. Plantago. The invasive plant P. virginica L. (American plantain) belongs to the subg. Plantago, whereas P. lanceolata L. (spear plantain) and P. aristata Michx. (long-flowered plantain) belong to subg. Psyllium.

Plantago coronopus L., commonly known as the buck’s-horn plantain, is characterized by having deeply pinnately lobed leaves, short hairs on the corolla tubes, and 3–4 locular capsules. It is known as a salt tolerant plant or halophyte (O’Kennon et al., 1998; Fekete et al., 2021). This species is native to Europe and the Mediterranean region (Chater and Cartier, 1976) and has been introduced to California, Texas, Hungary, and New Zealand (Dempster, 1993; O’Kennon et al., 1998; Meudt, 2012; Schmidt et al., 2016). Fekete et al. (2021) predicted a high likelihood of the plant occurring in other countries where it has not yet been reported, considering its rapid eastward spread. During a field survey in southern Korea in April 2022, the presence of P. coronopus was first confirmed in Gwangyang Port, Gwangyang-si, Jeollanam-do, Busan New Port, Changwon-si, and Gyeongsangnam-do (Fig. 1).

Here, we provide a detailed description and color photographs of this newly recorded invasive alien plant in Korea. This information can be utilized to help manage it effectively.

Field surveys were conducted in April 2022, and the examined materials were deposited in the Korea National Herbarium (KH). An absolute digital caliper (500-181-30, Mitutoyo, Kanagawa, Japan) was used to measure the morphological characteristics of the new alien species, while a microscope (Stemi 508, Carl Zeiss Microscopy GmbH, Göttingen, Germany) with an Axiocam ERc 5s camera was employed to observe specimens and capture photographs. The terminology used for description and comparison was taken from Li et al. (2011) and Lee et al. (2005).

Plantago coronopus L. Sp. Pl. 1: 115, 1753 (Figs. 2, 3).

Korean name: Sa-seum-ppul-jil-gyeong-i.

English name: Buck’s-horn plantain.

Herbs annual or perennial, hermaphroditic, scapose, ca. 25 cm tall. Roots taproot, tenuous, light brown. Leaves 20–35, rosette, spreading on the ground or ascending; petiole inconspicuous; leaf blade linear to narrowly oblong, 6.9–8.8 × 1.1–2.0 cm, dark green, margin pilose, gradually tapered to base, toothed or deeply pinnately lobed; lobes elliptic to linear, apex obtuse to acute. Inflorescence spikes, cylindrical, 2.8–7 cm × 4.4–4.98 mm, densely flowered; scapes ascending, 20.5–23.8 cm × 1.36–2.01 mm, pubescent with unicellular simple hairs; bracts broadly ovate, narrowly triangular to rarely triangular, 2.7–2.8 × 0.6–1.1 mm, green, red at tip, apex acuminate, margin ciliate. Flowers bisexual; calyces 4, ovate to elliptic, 2.1–2.2 × 1.1–1.3 mm, apex acute to obtuse, keeled, keel pilose, margin ciliate; corolla actinomorphic, corolla tube 2–2.1 × 0.58–0.6 mm, pubescent, corolla lobes 4, ovate, apex acute, 1.1–1.2 × 0.6–0.7 mm, white, red at base, glabrous; stamens 4; filaments exserted, 1.7–2.7 mm long, linear; anthers elliptical, reddish or yellow, 1.6–1.8 × 0.69–0.7 mm; ovary ellipsoid, 0.5–0.8 × 0.4–0.5 mm, ovules 3–4 per locule; style non-exserted, 1.5–1.8 mm long, hairy at base; stigma smooth. Fruits capsule, circumscissile, ellipsoid to oblong, 1.2–1.9 × 0.9–1.1 mm. Seeds ellipsoid to oblong (boat-shaped), 1–1.5 × 0.5–0.7 mm, black.

Flowering and fruiting: Late April to October.

Origin: Europe (Dodds, 1953; O’Kennon et al., 1998; Baker, 2005), western Asia (Baker, 2005), North Africa (POWO, 2024).

Introduced: North America (O’Kennon et al., 1998), Australia (Baker, 2005), New Zealand (Meudt, 2012), Korea (This study).

Habitat: Open coastal area.

Chromosome number: 2n = 20 (Mohsenzadeh et al., 2008; Bozdağ et al., 2015).

Specimens examined: Jeollanam-do: Gwangyang-si, 24 Apr 2022, S. W. Lee LSW2022090 (KH: KHB1654522); Gyeongsangnam-do: Changwon-si, 16 Oct 2022, S. W. Lee LSW2022428 (KH: KHB1654523).

Taxonomic note: The unrecorded species discussed here is referred to by its Korean name, Sa-seum-ppul-jil-gyeong-i (사 슴뿔질경이). It was previously reported by the Gyeongsan Agricultural Technology Center as a potential edible resource. At that time, the species was identified as P. insularis L.; however, no supporting records or traces of this scientific name are available. Based on the morphological descriptions provided in the original report, it is likely that the species was misidentified and actually corresponds to P. coronopus.

This species was first discovered in South Korea at Gwangyang Port and Busan New Port. Both locations feature sidewalk blocks near bridges. In particular, the sidewalk blocks at Gwangyang Port are covered with moss, creating a slightly humid environment. These areas host a mix of alien and native plant species. Among the alien species, Oenothera biennis L., Potentilla supina L. subsp. paradoxa (Nutt.) Soják, Oxalis dillenii Jacq., and Euphorbia maculata L. were observed. Meanwhile, native species such as Arenaria serpyllifolia L., Crepidiastrum sonchifolium (Bunge) J. H. Pak & Kawano, and Equisetum arvense L. were also present. Fewer than ten individuals of this species were initially observed at both sites. However, a continuous monitoring effort over three years confirmed the presence of stable populations, suggesting that the species is maintaining an ecologically viable state in these areas.

Morphologically, this species resembles P. weldenii Rchb. but is clearly different in the length of the scape. Plantago weldenii was previously considered a subspecies of P. coronopus (Arcangeli, 1882); however, Gamisans (1988) later reclassified it as a distinct species. Despite this, the phylogenetic relationships and taxonomic ranks of these species continue to be a topic of ongoing debate (Lazzaro et al., 2020).

Plantago coronopus can be divided into four subspecies. Among these, P. coronopus subsp. coronopus has a global coastal distribution, while the other three subspecies (P. coronopus subsp. cupanii, P. coronopus subsp. humilis, and P. coronopus subsp. macrorhiza) are restricted to the Mediterranean region. These subspecies differ in leaf morphology, habitat, and size, but comprehensive data on these variations remain limited.

This study confirms the introduction of P. coronopus, which is native to Europe, North Africa, and western Asia, to Korea (Dodds, 1953; O’Kennon et al., 1998; Baker, 2005; POWO, 2024). In Korea, 11 species of Plantago occur; among them, four are alien species, including the newly identified species. The genus Plantago in South Korea is currently classified into five subgenera (Rahn, 1996; Park and Kim, 1998). Three of these represent the four alien species: P. coronopus (subg. Coronopus), P. aristata (subg. Psyllium), P. lanceolata (subg. Psyllium), and P. virginica (subg. Plantago). These subgenera differ from the other two subgenera (subg. Littorella, subg. Bougueria) by having bilocular ovaries and pyxidial fruits (vs. unilocular ovary and small nut) (Rahn, 1996). The subgenus Coronopus, which includes P. coronopus, differs from subg. Psyllium, in which leaves alternate in a rosette (vs. opposite) and have two to six ovules (vs. two ovules) in the ovary. It is also distinguished from subg. Plantago by the short hairs on the corolla tube (vs. glabrous) (Rahn, 1996; O’Kennon et al., 1998). The four alien plant species in Korea are easily distinguished because of their distinct morphological differences, primarily in the scapes, leaves, inflorescences, and bracts (Fig. 3, Table 1).

The seeds of P. coronopus may be introduced and spread through intentional cultivation, as they were marketed by Johnny’s Selected Seed Company as an edible ornamental plant under the names “Minutina” and “Erba stella” in the specialty salad greens market. Although the introduction pathway in Korea is unclear, the presence of individuals found near ports suggests they were transported from overseas. Expanding road networks and increasing traffic have facilitated the spread of alien species (Fekete et al., 2021). Moreover, the use of de-icing salt during the winter for road maintenance can further promote the spread of halophytes like P. coronopus (Fekete et al., 2021). Additionally, the seeds of this species are resistant to drought, soil compaction, and competition, germinating well in low-moisture soils while demonstrating excellent survivability (Blom, 1992; Mook et al., 1992). Therefore, caution should be exercised to prevent their spread.