Acorus shannai C. L. Long & Z. Cheng, 2025

Acorus shannai C. L. Long & Z. Cheng sp. nov.

Figs 2 View Figure 2 , 3 “ 山柰菖蒲 ” (Shan Nai Chang Pu View Figure 3 )

Diagnosis.

The strong fennel aroma of the plant, distinct dorsal sutures on the fruit, and a spathe length 2–3 times that of the spadix are diagnostic features that differentiate A. shannai from other species in the A. gramineus group. The new species belongs to the A. gramineus group based on the following characteristics: Leaves without conspicuous marginal swellings of the lamina and a distinct midrib ( Li 1979). According to the key to the species of Acorus occurring in China ( Li 1979; Li et al. 2010), the morphology of A. shannai is similar to “ A. tatarinowii ” and A. gramineus . However, A. shannai can be clearly distinguished by the following features: the whole plant emits a strong fennel odor (vs. aromatic in “ A. tatarinowii ” and A. gramineus ), the fruit has distinct dorsal sutures (vs. inconspicuous dorsal sutures in “ A. tatarinowii ” and A. gramineus ), and the leaf-shaped spathe is approximately 2–3 times longer than the spadix (vs. more than 3 times in “ A. tatarinowii ”).

Type.

China • Guizhou Province: Qiandongnan Miao and Dong Autonomous Prefecture, Leishan County , 26°22'46.5"N, 108°7'53.4"E, alt. 1039 m a. s. l., 25 August 2021; Zhuo Cheng HXCP 024 ( KUN!). (holotype: KUN!; isotype: KUN!) GoogleMaps .

Description.

Herbs, perennials, helophyte plants. Plants 40–80 cm, without indumentum. Rhizome recumbent and stout, 10–20 × 0.5–0.8 (- 1.2) cm, strong Foeniculum vulgare – like aroma with fleshy fibrous roots, internodes, 0.6–0.7 cm. Leaf sheath, 0.7–1.5 cm, purple. Leaves several, about ten, light green, ensiform, 30–60 × 0.7–1.5 cm, midrib lacking, apex acuminate. The leaf base is folded in half, the middle is flat above, without distinct midrib, parallel veins up to 15 cm, and exceedingly slender but raised. Peduncles compressed triangular, 8–25 cm. Spadix is green and leaf-like, 10–41 cm., 2–3 times longer than Spadix. Spadix is straight or slightly curved, narrowly cylindrical to subcylindric, 5–13 × 0.5–0.7 cm, densely flowered, 3–4 flowers in one cross-section. Flowers are white, 1.5–1.7 mm. Infructescence, up to 1 cm thick, fruit sub oblong, yellow-green, 4–4.5 × 2–3 mm. Seeds oblong-ellipsoid to ovoid, 2.5–3 × 1–1.2 mm. Flower, May-June. Fruit, July-August. 2 n = 24.

Etymology.

The specific epithet is derived from the local name “ shannai ”.

Distribution, habitat, and phenology.

The locality of this taxon is Leishan County, located in the Qiandongnan Miao and Dong Autonomous Prefecture of Guizhou Province. Specimen records indicate this species is also distributed in Guangxi, Hunan, and surrounding areas (Fig. 4 View Figure 4 ). A. shannai exhibits a preference for moist mountain slopes and brook-adjacent habitats, distinguishing it ecologically from other Acorus species. It typically grows at an elevation of less than 1,500 m a. s. l. The species has been observed flowering in May to June and fruiting in July to August.

Taxonomic notes.

The new species identified belong to the A. gramineus group, characterized by the following characteristics: leaves without conspicuous marginal swellings of the lamina and a distinct midrib ( Li 1979). Previous studies have demonstrated the presence of three species within this group in China based on multiple lines of evidence: Acorus macrospadiceus , “ A. tatarinowii ” and A. gramineus ( Cheng et al. 2020) . Through a comparative analysis of morphological characteristics, distribution locations, and type specimens, we have concluded that it is incorrect to elevate A. gramineus var. macrospadiceus Yamam. to species level.

According to the key to the species of Acorus occurring in China ( Li 1979; Li et al. 2010), the morphology of A. shannai is similar to “ A. tatarinowii ” and A. gramineus . However, A. shannai can be distinguished by several features: the whole plant has a strong fennel odor, most of the fruits remain immature, and the leaf-shaped spathe is approximately 2–3 times longer than the spadix. A comparative summary of the characters among these three taxa is presented in Table 1 View Table 1 .

From a geographical distribution perspective, “ A. tatarinowii ” and A. gramineus are distributed in southern China, whereas A. shannai is limited to a few provinces, with east Guizhou serving as its distribution center. The ecological habits of these species differ significantly. “ A. tatarinowii ” is an aquatic plant, while A. gramineus and A. shannai are terrestrial taxa. “ A. tatarinowii ” is an epiphytic plant on rocks and in fast-flowing brooks. A. gramineus grows in drier soil with lower humidity, and A. macrospadiceus grows in moist soil with higher humidity ( Cheng et al. 2020).

Our previous research demonstrated that the volatile oil extracted from both the rhizomes and leaves of A. macrospadiceus primarily contains estragole, β - caryophyllene, trans-anethole, β - elemene, and endo-borneol, and estragole is the main component ( Shu et al. 2018 b). In contrast, it has been reported that the main volatile components of “ A. tatarinowii ” were α-asarone, β - asarone, and γ-asarone through GC-MS analysis, with β - asarone being presented in the highest quantities ( Jaiswal et al. 2015).

In terms of traditional uses, “ A. tatarinowii ” has widely been used as herbal medicine for multiple medicinal purposes in China for more than 2,000 years, particularly for treating central nervous system diseases. It has been included in the Chinese Pharmacopoeia since its first edition as a foundational plant in traditional Chinese medicine known as Shichangpu. A. gramineus is often used in creating miniascapes because of its unique aroma and ornamental value. Meanwhile, Acorus shannai serves as a common seasoning in dishes featuring Artiodactyla or fish in southern China, especially in markets of Guizhou and Guangxi, southern Yunnan, western Hubei and Hunan. Local ethnic groups and Han Chinese have also removed wild populations of A. shannai to their gardens for easier access.

The local herbal traders often purchase and sell A. shannai in large quantities, mistakenly labeling it as “ A. tatarinowii ”, which may lead to overharvesting. More importantly, due to the varying chemical compositions among different species, the misuse or abuse of the wrong Acorus species could pose a threat to clinical safety.

The formal recognition of A. shannai contributes to the resolution of long-standing ambiguities within the A. gramineus group and highlights the importance of integrating morphological and genomic approaches in plant taxonomy.

Preliminary conservation status.

Acorus shannai is commonly used as a seasoning in southern China, particularly in regions such as Guizhou, Chongqing, Guangxi, and the surrounding areas. It is commonly found in local markets and is favored for its aromatic properties in culinary applications, especially in meat and fish dishes. However, numerous specimens recorded of this plant in various herbariums indicate a significant interest in its botanical classification. Research indicates that most A. shannai resources are derived from cultivation rather than wild populations, which appear to be limited. Without comprehensive biogeographical studies, A. shannai may be classified as “ data deficient ” (DD) according to IUCN criteria. This classification arises from insufficient information to assess its risk of extinction based on distribution and population status ( IUCN 2024). Moreover, the unclear taxonomic status of A. shannai leads to confusion in the marketplace, where it is often sold under the name “ A. tatarinowii ”. This misidentification poses risks not only to drug safety but also threatens the sustainable use of A. shannai populations. The distinction between these two species is crucial as they are perceived differently by local communities; while they share morphological similarities, locals differentiate them based on their aroma and habitat preferences. Given the reliance on cultivated populations for culinary use and the limited distribution of wild populations, targeted conservation strategies, such as habitat protection and propagation, are critical for sustainable utilization.

Additional A. shannai specimens examined (paratypes).

Acorus shannai – China • Guizhou: Qiandongnan Miao and Dong Autonomous Prefecture, Leishan County , 26°22'46.5"N, 108°7'53.4"E, 1039 m a. s. l., 25 August 2021, Zhuo Cheng HXCP 031 ( KUN, 5 duplicates) GoogleMaps • Guangxi: Longsheng County, 21 March 2014, Longsheng County census team, 450328140321050 LY ( IBK) • Longsheng County, 10 April 1984, F. N. Wei 01713133 ( PE) • Jinxiu Yao Autonomous County, 9 June 1958, Y. K. Li 00141407 ( IBK) • Guangdong: Fengshun County, 19 May 1958, X. G. Li 00141420 ( IBK) • Hunan: Nanyue District , 10 April 1944, B. H. Liang 00141422 ( IBK) • Chengbu County, 16 May 2015, D. G. Zhang et al. CB 20150516 _ GT 0151 ( JIU) .