Mat-forming graminoid herb growing in fairly dense stands due to extravaginal horizontal, branched rhizomes, typically with short rhizome branches up to 2 cm long and ca. 2 mm broad between aerial shoots. Aerial shoots erect or ascending from rhizome, with several prophylls (reduced leaves without or with a short blade), tinged in pink or scarlet. Culms 10–25 mm, erect, smooth and glabrous. Base of shoots with numerous withered leaves forming a fairly dense cylinder of sheaths. Leaf sheaths scarlet or purple. The entire plant has a strong smell (coumarin).

Leaves folded (convolute) or sometimes flat or filiform (involute), with numerous veins distinctly raised on the upper surface, smooth, glabrous on the lower surface, pubescent with very short, stiff hairs on the upper surface. Basal leaves 10–20 cm long, very narrow, 0.8–1.0 mm, gradually tapering towards apex. Culm leaves 2–3, much shorter (up to 4–6 cm) but often much broader (up to 3.5–4.0 mm) than basal leaves and rapidly reduced in length upwards on the culm; the flag leaf with a very short blade, 0.3–1.0 cm, attached around the middle of the culm or below. Ligula 0.3–1.0 mm, truncate, distinctly ciliate.

The units of the inflorescence of Poaceae are the spikelets, nearly always numerous in a panicle or spike-like inflorescence. Spikelets are composed of 2 glumes (bracts for the spikelet) and one or more flowers (the term used below) or rather floral units often named ‘florets’ because we do not know what is the exact flower. A flower or floret is composed of: a lemma with 1 mid vein (probably the floral bract), a palea with 2 mid veins (either 2 fused bracteoles or perhaps 2 fused perianth leaves), 3 small organs called ‘lodiculae’ being essential in the opening of the flower at anthesis (possibly transformed perianth leaves or transformed stamens), 3 stamens (mostly), and a gynoecium of 2 fused carpels with 2 feathery stigmas and one seed.

Inflorescence a moderately dense, ovoid panicle, 2.5–5 × 1–2.5 cm, occupying ca. 1/5–1/8 of culm length, with slender, ascending branches. Panicle with 5–7 nodes and with 2–4 branches at each of the lower nodes. Branches smooth, 1–2 cm long, each usually with 1–2 spikelets in their distal parts. Spikelets 4–7 × 2.5–3.5 mm, with 3 flowers apparently at the same level, the two lateral ones male (staminate), the central one bisexual. Bracts (glumes and lemmas) with weakly marked keel. Glumes ovate to lanceolate, acute to acuminate with an often lacerate apex, unawned, with 1(3) veins, smooth and glabrous, variegated in green (mid part), violet–purple, and with the broad hyaline margin golden yellow, subequal, lower glume 4–6 mm, upper glume 5–7 mm, as long as the spikelet (usually the longest bracts in the spikelet). Lemmas 4–5 mm, lanceolate, acute, bifid in the bisexual flower, 3-veined, more or less green, pilose with long hairs or more rarely short ones along the entire length in male flowers, apically in bisexual flowers. Lowermost male flower with a very short awn (ca. 1 mm) from the upper 1/3 of the keel; uppermost male flower with a 4–6 mm long, geniculate awn from the lower 1/3 of the keel; the bisexual flower unawned. Paleas shorter than and included by the lemmas, deeply bifid into two long awns. Anthers 1.2–1.4 mm, well developed in some Svalbard plants, shrivelled in others.

Fruit an achene (with one seed).

Sexual or asexual reproduction by seeds; local vegetative reproduction by fragmentation of mats. Wind pollinated. Seed set is probably intermittent (Allred & Barkworth 2007). Seeds germinate to 14–15 % (Alsos et al. 2013).

The diaspore (probably the spikelet with fruit, except the glumes) is spread rather passively but some wind and animal dispersal is possible due to the awn and the hairy lemmas.

There is nothing similar to this species among Svalbard grasses.

Dry heaths with Dryas, Cassiope and partly Salix polaris, on well-drained, mostly fairly coarse substrates. The entire distribution in Svalbard is located in areas with sedimentary rocks and circumneutral substrates. The species is missing from areas with acidic substrate and also from calcareous areas.

Nearly the entire range of Hierochloë alpina is located within the middle arctic tundra zone and the weakly continental section. The species is concentrated to the central parts of Spitsbergen with its known localities on the peninsula between Isfjorden and Van Mijenfjorden (Nordenskiöld Land) and in the Kapp Thordsen area (Dickson Land) and on Bohemanflya (Oscar II Land) on the north coast of Isfjorden. There is, however, an isolated locality in Mosselhalvøya northernmost in Ny-Friesland, east of the mouth of Wijdefjorden (here documented by herbarium voucher).

The global range is circumpolar and reaching south to the C Asian mountains, in the Rockies south to the border between Canada and the U.S., in E North America south to Labrador and Quebec, and in Europe south to the mountains of N Scandinavia.

Hierochloë alpina is an uncommonly monomorphic species throughout its vast range. The only variation is found in NE North America and SW Greenland, where a separate subspecies or species overlaps or co-occurs with H. alpina: H. orthantha T.J.Sørensen (Hierochloë alpina ssp. orthantha (T.J. Sørensen) G.Weim.; Anthoxanthum monticolum (Bigelow) Veldkamp ssp. monticolum; see Allred & Barkworth 2007). The group has been extensively studied by Weimarck (1970a, 1970b, 1971 etc.) who showed that H. alpina is a facultative apomict, as also suggested by the variation in anther development in Svalbard. It is mainly octoploid (2n = 56) but with additional, higher numbers in the very well investigated Nordic regions (Weimarck, see above).

Many authors (e.g., Soreng et al. 2003; Allred & Barkworth 2007) merge the genera Anthoxanthum L. and Hierochloë R.Br. under the former name (see the synonymy above). The justification for this is found in Schouten & Veldkamp (1985), mainly based on a morphological study of SE Asian plants. We refrain from this due to several differences in assumed taxonomically important morphological features and a different base chromosome number: Anthoxanthum has x = 5, Hierochloë x = 7). See also Connor (2012) who studied the same floral characters as Schouten & Veldkamp and reversed their conclusions.

Allred, K.W. & Barkworth, M.E. 2007. Anthoxanthum L. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico. 24. Magnoliophyta: Commelinidae (in part): Poaceae, part 1: 758–764.

Alsos, I.G., Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.

Connor, H.E. 2012. Flowers and floral biology of the holy grasses (Hierochloe and Anthoxanthum, Aveneae, Gramineae). – Flora 207: 323–333.

Schouten, Y. & Veldkamp, J.F. 1985. A revision of Anthoxanthum including Hierochloe (Gramineae) in Malesia and Thailand. – Blumea 30: 319–351.

Soreng, R.J., Peterson, P.M., Davidse, G., Judziewicz, E.J., Zuloaga, F.O., Filgueiras, T.S. & Morrone, O. 2003. Catalogue of New World grasses (Poaceae): IV. Subfamily Pooideae. – Contributions from the U.S. National Herbarium 48. 730 pp.

Weimarck, G. 1970a. Hierochloë alpina (Gramineae) 2n=66 in northern Finland. – Botaniska Notiser 123: 201–202.

Weimarck, G. 1970b. Apomixis and sexuality in Hierochloë alpina (Gramineae) from Finland and Greenland and in H. monticola from Greenland. – Botaniska Notiser 123: 495–504.

Weimarck, G. 1971. Variation and taxonomy of Hierochloë (Gramineae) in the northern hemisphere. – Botaniska Notiser 124: 129–175.