Anthoxanthum horsfieldii (Kunth ex Benn.) Reeder

Anthoxanthum horsfieldii is a variable species of mountains in SE Asia, extending into India. There are small differences between the populations from different islands or mountain areas, and these populations are sometimes recognized at varietal rank. However, this approach has led to a proliferation of varieties based on overlapping, only partially segregating characters and is not followed here.

Both lower florets appear to be sterile and epaleate in Taiwan, but in SE Asia the first floret may sometimes be staminate with a palea. Anthoxanthum horsfieldii is in fact very close to A. hookeri from the Himalayas, which differs in little more than its rather looser panicle and acute lemma lobes.

Plant loosely tufted, shortly rhizomatous. Culms 10–60 cm tall, 3–5-noded. Leaf sheaths glabrous or sparsely pilose; leaf blades loosely involute, 6–13 cm, 2–5 mm wide, glabrous or adaxial surface pubescent; ligule 2–4 mm, truncate. Panicle narrow, contracted, 2.5–7 cm; branches up to 5 cm; pedicels pubescent. Spikelets lanceolate-oblong, 4.3–5.5 mm; glumes unequal, glabrous, lower glume 2/3 to 3/4 length of upper glume, 1-veined, upper glume as long as spikelet, 3-veined; lower florets sterile, composed only of lemmas, ca. 4 mm, pilose on back, apex 2-lobed, lobes obtuse; first lemma awned from above middle, awn straight, 0.8–1.5 mm; second lemma awned from lower 1/4–1/3, awn geniculate, 4.5–6 mm; bisexual floret 2.5–3 mm, smooth, shiny; anthers 1.5–2 mm. Fl. Oct.

Guizhou, Taiwan [India, Japan, Malaysia, New Guinea, Philippines, Thailand].

Mountains, grassy places, in sun or shade; 2500–3300 m.

Ataxia horsfieldii Kunth ex Bennett, Pl. Jav. Rar. 8. 1838; Anthoxanthum formosanum Honda; A. horsfieldii var. formosa-num (Honda) Veldkamp; A. horsfieldii var. viridescens (Honda) Veldkamp; A. japonicum (Maximowicz) Hackel ex Matsumura subsp. luzoniense (Merrill) T. Koyama; A. luzoniense Merrill; A. viridescens Honda; Hierochloë horsfieldii (Kunth ex Bennett) Maximowicz.