Gastrodia dayaoshanensis Xiong Li, Ying Qin & A.Liu, sp. nov. (Fig. 1)

Type:— CHINA. Guangxi: Jinxiu County, Dayaoshan National Nature Reserve, elev. ca. 1555 m, 10 September 2025, Ying Qin GXQY20250910001 (holotype IBK!; isotypes IBK!).

Diagnosis:—The new species is similar to G. peichatieniana, G. longistyla and G. menghaiensis, but it can be distinguished from G. peichatieniana mainly by its brown (vs. white or tinged brown) flowers, sepals and petals entire or with a few teeth (vs. minutely fimbriate) at margin, united portion of lip with (vs. without) 2 longitudinal ridges, and from G. longistyla mainly by its 2.7–3.2 mm (vs. 1.2–2.2) wide free portions of sepals, united portion of lip with (vs. without) 2 longitudinal ridges, stigma without (vs. with) needle-shaped appendage, and from G. menghaiensis mainly by its brown (vs. white) and straight (vs. curved) perianth tube, sepals and petals entire or with a few teeth (vs. minutely fimbriate) at margin, united portion of lip without (vs. with) 2 calli at base.

Holomycotrophic herbs, 16.1–59.6 cm tall. Rhizomes cylindrical, red-brown, 1.0–4.0(7.2) cm long, 2.8–9.9(18.1) mm in diameter, covered with many lanceolate scales and root-hair-like hairs. Roots 3–6, 1.4–18.5 cm long, 0.6–0.9 mm in diameter. Stem erect, 13.9–49.3 cm long, 1.2–3.5 mm in diameter, pale brown or brown, (3)4–10 noded, with membranous, brown, 4.0–10.0 mm long sheaths; the upper (0)1–4 sheaths ovate-lanceolate or lanceolate, other sheaths tubular. Inflorescence terminal, racemose, with 3–14(22) flowers; rachis (1.5) 3.7–10.5 cm long, 1.0– 2.2 mm in diameter, pale brown or brown. Floral bracts ovate, membranous, brown, 2.6–4.5 mm long. Flowers spreading horizontally or erect, not widely opening. Ovary brown, 3.2–4.2 mm long, 1.4–1.8 mm in diameter; pedicel 1.7– 3. 8 mm long, 0.7–0.9 mm in diameter. Sepals and petals united and forming a 5-lobed perianth tube. Perianth tube cylindrical, 8.9–9.7 mm long, 3.6–4.3 mm in diameter, brown, outer surface inconspicuously verrucose. Sepals connate 7/9–6/7 their lengths with petals, lateral ones connate 5/8–3/4 with each other; free portion of dorsal sepal broadly triangular, apex obtuse and retuse, 2.0– 2.2 mm long, 2.9–3.2 mm wide, margin entire or with a few teeth; free portions of lateral sepals broadly triangular, 2.3–2.6 mm long, 2.7–3.2 mm wide, apex obtuse, margin entire or with a few teeth; free portions of petals ovate or broadly ovate, 1.5–1.8 mm long, 1.2–1.4 mm wide, apex obtuse, margin entire or with a few teeth. Free portion of lip ovate, 2.9–3.4 mm long, 1.7–2.1 mm wide, margin slightly involute, entire or with a few teeth, adnate to perianth tube 3.6–4.3 mm above base; united portion of lip with 2 longitudinal ridges, red-brown below middle of ridges. Column white, 5.4–6.1 mm long, 1.4–1.9 mm wide, with obviously winged sides, grey-brown and with a stigma at base, 3-lobed at apex; midlobe rectangular, with pollinaria and anther cap at apex, each lateral lobe with a small tooth at apex; rostellum at about 2/3 of length of column, small; stigma ovate. Anther cap hemispheric, 1.0– 1.2 mm in diameter; pollinia 2, granular-farinaceous, pollen massulae loosely contained within anther cap. Capsules elliptic or cylindrical, 1.2–1.5 cm long, 3.1–4.5 mm in diameter, red-brown or brown; pedicel elongating to 4.6–9.9 mm long in fruit.

Phenology: —Flowering and fruiting in August and September.

Etymology: —The epithet “ dayaoshanensis ” refers to Dayaoshan National Nature Reserve, Jinxiu county, Guangxi, China.

Vernacular name: —大ẈƜ天※ (Chinese pinyin: dà yáo shān tiān mā).

Taxonomic notes: —There are 11 species of Gastrodia in Guangxi, and G. dayaoshanensis is similar to G. peichatieniana. Meanwhile, this new species is also similar to G. longistyla and G. menghaiensis distributed in Yunnan. Shared characters of the four similar species mainly include self-pollinated flowers, cylindrical and not widely opening perianth tube, triangular free portions of sepals, free portion of lip adnate to perianth tube near or above middle. However, this new species can be easily distinguished from the other three by its unique characters presented in the diagnosis above. A detailed morphological comparison between G. dayaoshanensis and G. peichatieniana, G. longistyla, G. menghaiensis is showed in Table 1.

Distribution and ecology: — Gastrodia dayaoshanensis is only discovered growing in wet soil among leaf litter in Dayaoshan National Nature Reserve, Jinxiu county, Guangxi, China. The two populations are distributed in subtropical mixed coniferous and broad-leaved forests. One population is at an elevation of 1546–1557 m, while another population is at an elevation of ca. 1733 m. They are associated with Podocarpus wangii, Rhododendron sp., Cleyera japonica, Itea chinensis, Acer davidii, Cinnamomum sp., Pileostegia viburnoides, Rubus sp., Begonia fimbristipula, Elatostema sp., Bulbophyllum tokioi, Gastrodia peichatieniana, Goodyera viridiflora, Ophiorrhiza japonica, Sedum sp., Oreocharis argyreia, O. magnidens, Goniophlebium amoenum, Plagiogyria euphlebia, Asplenium normale, Arthromeris lehmanni, Hymenophyllum sp.

Additional specimens examined (paratypes): — CHINA. Guangxi: Jinxiu County, Dayaoshan National Nature Reserve, elev. ca. 1554 m, 23 September 2024, Ying Qin GXQY20240923001 (IBK!); CHINA. Guangxi: Jinxiu County, Dayaoshan National Nature Reserve, elev. ca. 1550 m, 13 September 2025, Ang Liu, Lu Zhu & Yong Xie LADYS01 (CSH!).