Description from Flora of China
Hierochloë R. Brown.
Perennial, fragrant herbs. Inflorescence an open or contracted panicle. Spikelets lanceolate to plumply elliptic or oblong, weakly laterally compressed, florets 3, brown, lower 2 florets staminate or sterile, terminal floret bisexual; rachilla disarticulating above glumes but not between florets. Glumes persistent, unequal to subequal, lanceolate to ovate, lower glume shorter, 1(–3)-veined, upper glume 3(–5)-veined, about as long as spikelet, apex acute. Lower 2 florets subequal, with a palea and 3 stamens, or sterile and epaleate, or a combination of both; lemmas equal to or shorter than upper glume, firmly membranous to leathery, often brown-pilose on back and ciliate along margins, apex emarginate to deeply 2-lobed, awnless, with a short straight awn from above middle, or geniculately awned from near base. Bisexual floret equaling or shorter than 2 lower florets; lemma cartilaginous, glossy, 3–5-veined, margins convolute and covering palea, apex awnless, rarely mucronate; palea 1–3-veined, without keels; lodicules absent or 2; stamens 2; stigmas plumose. x = 5, 7.
All species are scented with coumarin (C9H6O2), and some are used medicinally for their coumarin content.
Hierochloë has traditionally been recognized on the basis of the two lower florets being staminate, paleate, and awnless or only shortly awned, in contrast to the sterile, epaleate, geniculately awned lower florets in typical Anthoxanthum. Lodicules are also absent in typical Anthoxanthum. However, it is now known that a considerable number of species is intermediate in these characters, including some in China, and also some (e.g., A. hookeri) where the sex of the lower florets is variable within the species. There is no justification for continuing to recognize two separate genera. The species are all clearly related by their unusual spikelet structure and by the presence of coumarin.
About 50 species:temperate and cold regions of both hemispheres, also on tropical mountains; ten species (three endemic) in China.
(Authors: Wu Zhenlan (吴珍兰); Sylvia M. Phillips)