Anthoxanthum L.

Kelly W. Allred
Mary E. Barkworth

Plants annual or perennial; densely to loosely cespitose, sometimes rhizomatous; fragrant. Culms 4–100 cm tall, erect or geniculata, sometimes branched; internodes hollow. Leaves cauline or basally concentrated, glabrous or softly hairy; sheaths open; auricles absent or present; ligules membranous, sometimes shortly ciliate or somewhat erose; blades flat or rolled, glabrous or sparsely hairy. Inflorescences open or contracted panicles, sometimes spikelike. Spikelets pedicellate or sessile, 2.5–10 mm long, laterally compressed, stramineous to brown at maturity, with 3(4) florets, lowest 2 florets usually staminate or sterile, sometimes reduced to dorsally compressed lemmas, subequal to or exceeding the distal floret, distal floret bisexual; rachilla not prolonged beyond the base of the distal floret; disarticulation above the glumes, the florets falling together. Glumes unequal or subequal, equaling or exceeding the florets, lanceolate to ovate, glabrous or pilose, keeled; calluses blunt, glabrous or hairy; lowest 2 florets: lemmas strongly compressed, 3-veined, strigosa, hairs brown, apices bilobed, unawned or dorsally awned; distal florets: lemmas somewhat indurate, glabrous or with hairs, shiny, inconspicuously 3–7-veined, unawned; paleas 1-veined, enclosed by the lemmas; lodicules 2 or absent; anthers 2 or 3. Caryopses shorter than the lemma, concealed at maturity, tightly enclosed in the floret; hila less than 1/3 the length of the caryopses, oval. x = 5. Name from Greek anthos, ‘flower’, and Xanthos, ‘yellow’, alluding to the golden color of the panicles of Anthoxanthum sensu stricto.

Anthoxanthum is a cool-season genus of about 50 species that grow in cool temperate and arctic regions throughout the world. There are seven species in North America north of Mexico, five of which are native.

This treatment follows the recommendation of Schouten and Veldkamp (1985) in merging Anthoxanthum and Hierochloë into a single genus which, in accordance with the International Code of Botanical Nomenclature, has to be called Anthoxanthum. The two genera are quite distinct in North America but, according to Schouten and Veldkamp, intergrade in Asia. The recommendation was endorsed by Zhenlan Wu and Sylvia M. Phillips (2006) in the Flora of China but it is not universally accepted.

Phalaris resembles Anthoxanthum sensu lato in its spikelet structure, differing in the greater reduction of its lower florets and in not being fragrant when crushed. Anatomical studies (Pizzolato 1984) also support the close relationship of Anthoxanthum and Phalaris. Pizzolato also stated that, although the bisexual florets of Hierochloë are described as terminal, a microscopic fourth floret is developed distal to the third (bisexual) floret.

The fragrance emitted when fresh plants are crushed or burned is from coumarin. In addition to smelling pleasant, coumarin has anti-coagulant properties. It is the active ingredient in Coumadin, a prescription drug used to prevent blood clots in some patients after surgery. A disadvantage of coumarin is that it is metaboloized by species of the fungal genus Aspergillus to dicoumarol. This induces vitamin K deficiency and a susceptibility to hemorrhaging in wounded animals. Because of this, using moldy hay containing Anthoxanthum as feed is dangerous.

Wherever they grow, the species that used to be treated as Hierochloë (species 3– 7 in this treatment) have been used by native peoples. Native Americans used them for incense, baskets, and decorations, in addition, they steeped them in water for a hair-, skin- and eyewash and also used them for a cold medicine, analgesic, and insecticide. Early Europeans spread the species in churches at festivals. They can also be used to make ale (Stika 2003).

November 2010: We accidentally failed to post the treatment of Anthoxanthum earlier, a point that was brought to my attention on November 26, 2010. Unfortunately, the original file is not permitting changes to be made so I am now retyping it. I am giving priority to the parts that will be of greatest interest to the person who inquired about its availability. The remaining species descriptions will be made available before the end of 2010. I have made some revisions. All are minor to trivial (addition of one reference; changes in phrasing). M. Barkworth

SELECTED REFERENCES. Aiken, S.G., L.L. Consaul, and M.J. Dallwitz. 1995 on. Grasses of the Canadian Arctic Archipelago: Descriptions, illustrations, identification, and information retrieval.; Belk, E. 1939. Studies in the anatomy and morphology of the spikelet and flower of the Gramineae. Ph.D. dissertation, Cornelll University, Ithaca, New York, U.S.A. 183 pp.; Hedberg, I. 1990. Morphological, cytotaxonomic and evolutionary studies in Anthoxanthum odoratum L. sens. lat.–A critical review. Sommerfeltia 11:97–107; Hitchcock, A.S. 1951. Manual of the Grasses of the United States, ed. 2, rev. A. Chase. U.S.D.A. Miscellaneous Publication No. 200. U.S. Government Printing Office, Washington, D.C., U.S.A. 1051 pp.; Norstog, K.J. 1960. Some observations on the spikelet of Hierochloë odorata. Bull. Torrey Bot. Club 87:95–98; Pizzolato, T.D. 1984. Vascular system of the fertile floret of Anthoxanthum odoratum L. Bot. Gaz. 145: 358–371. Schouten, Y. and J.F. Veldkamp. 1985. A revision of Anthoxanthum including Hierochloë (Gramineae) in Malaysia and Thailand. Blumea 30:319–351; Stika, J. 2003. Sweetgrass ale. Weimarck, G. 1971. Variation and taxonomy of Hierochloë (Gramineae) in the Northern Hemisphere. Bot. Not. 124: 129—175. Weimarck, 8. 1987. Hierochloë hirta subsp. praetermissa , subsp. nova (Gramineae, an Asiatic-European taxon extending to N and C Europe in the Northern Hemisphere. Symb. Bot. Upsal. 2: 175–181. Wu, z. and S.M. Phillips. 2006. Anthoxanthum, p. 336–339 in Wu, Z., P.H. Raven and D. Hong (Eds.). Flora of China, vol. 22. Science Press, Beijing, China and Missouri Botanical Garden Press, St. Louis, Missouri, U.S.A.

1. Glumes unequal, the lower glumes shorter than the upper glumes; lowest 2 florets sterile: 2

2. Plants annual; ligules 1–3 mm long; blades 1–5 mm wide; panicles 1–4 cm long: A. aristatum

2. Plants perennial; ligules 2–7 mm long; blades 3–10 mm wide; panicles 3–14 cm long: A. odoratum

1. Glumes subequal; lowest florets staminate: 3

3. Staminate lemmas awned, the awns of the upper staminate lemma 4.5–10.5 mm long; plants densely to loosely tufted, the rhizomes rarely more than 2 cm long A. monticola

3. Staminate lemmas unawned or with an awn no more than 1 mm long; plants long-rhizomatous: 4

4. Panicles spikelike, 0.3–0.5 cm wide, with 1–2 spikelets per branch; rhizomes 0.3–1 mm thick; plants of the high arctic: A. arcticum

4. Panicles not spikelike, 1–10 cm wide, the longer branches usually with 3 or more spikelets; rhizomes 0.7–3 mm thick; plants of temperate and arctic regions:5

5. Lowest staminate lemma in each spikelet narrowly elliptic, its length more than 5 times its width; glumes equaling or slightly exceeded by the tips of the bisexual florets; blades 3-15 mm wide A. occidentale

5. Lowest staminate lemma in each spikelet elliptic, its length usually no more than 4 times its width; glumes exceeding the bisexual floret; blades 2–8 mm wide 6

6. Longest hairs on the distal portion of the bisexual florets 0.5–1 mm long, evenly distributed around the lemma tip: A. hirtum

6. Longest hairs on the distal portion of the bisexual floret mostly less than 0.5 mm long, longer hairs, if present concentrated near the midvein: A. nitens

Anthoxanthum aristatum Boiss.


Plants annual. Culms 5–60 cm tall, often geniculate at the base, freely branched. Auricles to 0.5 mm long, sometimes absent; ligules 1–2(3) mm long, obtuse to acute; blades 0.8–6 cm long, 1–5 mm wide. Panicles 1–4 cm long; lowest branches 8–12 mm long; pedicels 0.1–0.3 mm long, pubescent. Spikelets (4)5–9 mm long; lower glumes 3–5 mm long; upper glumes 5–7 mm long; sterile florets about 3 mm long, awn of the first floret 3.5–5 mm long, awn of the second floret 6–10 mm, exceeding the upper glumes by 2–3 mm; bisexual florets about 2 mm long; anthers 2, 2.8–4.1 mm long. 2n = 10, 20.

Anthoxanthum aristatum is native to Europe. It is not established but not common in North America, being found in mesic to dry, open, disturbed habitats of western and eastern part of the continent. All North American plants belong to Anthoxanthum aristatum Boiss. subsp. aristatum which differs from A. aristatum subsp. macranthum Valdés in having well-exserted awns and deeply bifid sterile lemmas.

Hitchcock (1951) stated that another annual species of Anthoxanthum, A. gracile Biv. is occasionally cultivated fro dry bouquets but it does not appear to be widely available at present. It differs from A. aristatum in having longer spikelets (1012, not 49, mm long) and simple or sparingly branched culms.

Anthoxanthum odoratum L.

Sweet Vernalgrass, Flouve Odorante, Foin d'Odeur

Plants perennial. Culms (10)25–60 (100) cm tall, erect, simple or sparingly branched. Auricles 0.5–1 mm, pilose-ciliate, sometimes absent; ligules 2–7 mm long, truncate; blades 1–31 cm long, 3–10 mm wide. Panicles (3)4–14 cm long, the spikelets congested; lowermost branches 10–25 mm long; pedicels 0.5–1 mm long, pubescent. Spikelets 6–10 mm long; lower glumes 3–4 mm long; upper glumes 8–10 mm long; two lowest florets sterile, 34 mm long, awn of the first lemma 2–4 mm long, awn of the second lemma 4–9 mm long, equaling or only slightly exceeding the upper glumes; bisexual florets 1–2.5 mm long; anthers 2, (2.9)3.5–4.8(5.5) mm long. 2n = 10, 20.

Anthoxanthum odoratum is native to southern Europe. In North America, it grows in meadows, pastures, grassy beaches, old hay fields, wasteplaces, and openings in coniferous forests (occasionally in dense shade) or as a weed in lawns. It is most abundant on the western and eastern sdes of North America and is almost absent from the central region. In southern British Columbia, it is rapidly invading the moss-covered bedroockof coastal bluffs and will soon exclude many native species. Diploids (2n = 10) have been referred to A. odoratum subsp. alpinum (À. Löve & D. Löve) Hultén. Because the two ploidy levels can be distinguished only through cytological analysis (Hedberg 1990), the two subspecies are not recognized in this treatment.

Anthoxanthum odoratum used to be included in hay and pasture mixtures to give fragrance but this practice is waning. The aroma is released on wilting or drying. By itself, the species unpalatable because of the bitter-tasting coumarin.

Anthoxanthum monticola (Bigelow) Veldkamp

Alpine Sweetgrass, Hierochloë alpine

Plants perennial; densely to loosely cespitose, rhizomes to 2 cm long (rarely longer), about 2 mm thick. Culms 20–55(75) cm tall. Basal sheaths glabrous, brown to deep purple; ligules 0.2–1.5 mm long, truncate, ciliate; blades 1–12 cm long, (0.7)1–3(5) mm wide, flat or folded, abaxial surface glabrous, shiny, adaxial surface sparsely scabrous or pilose. Panicles 1–8.5 cm long, 1.2–2 cm wide, with (3)10–20(35) spikelets. Spikelets 58 mm long, tawny; rachilla internodes about 0.1 mm long, glabrous. Glumes subeqaul, 4.8–6.7 mm long, about equaling the lemmas; lowest 2 florets in each spikelet staminate; lemmas 4–6.5 mm long, moderately hairy, hairs to 1 mm long, lemma tips deeply bifid, awned, awn of first lemma 0.4–4(6.5) mm long, awn of second second lemma 4.5–10.5 mm long, usually geniculate, arising from neat the base to above midlength; bisexual lemma 3.55.2 mm long, pubescent towards the bifid tip; anthers 1.5–2.7 mm long. 2n = 56, 58, 63, 66, 72.

Anthoxanthum monticola is circumpolar, usually growing north of the treeline, occasionally in open forets. It grows sporadically on well-drained, weakly acidic to neutral sand, gravel, and rocky barrens in most of arctic North America. It is not common to the south, even at high elevations.

Anthoxanthum monticola is facultatively apomictic but slow to set seed. Revegetation is best accomplished begetatively. It is listed as threatened or endangered in many parts of its range. There are two subspecies in North America.

1. Awns of the upper staminate florets 510.5 mm long, attached from near the base to about midlength; awn usually strinagly geniculate, the lower portion usually twisted with 24 gyres..... subsp. alpinum

1. Awns of the upper staminate florets 4.57 mm long, attached at or above midlength, not or weakly geniculate, the lower portion not twisted or twisted with 12 gyres ......subsp. monticola.

Anthoxanthum monticola subsp. alpinum (Sw. ex Willd.) Soreng

Awns of upper staminate florets 510.5 mm long, attached from near the base to midlength, usually strongly geniculate, the lower portion twisted with (1)24 gyres. 2n = 56, 66, 72.

Anthoxanthum monticola subsp. alpinum is the common subspecies in North America, extending from western Alaska to eastern Greenland and south to the Canadian border in the Rocky Mountains but, east of these mountains, it is mostly north of 60° N except in Quebec and Labrador where it extends south to about 53° N. It usually grows above or north of the treeline in places that are strongly exposed to the wind and have little snow cover during the winter.

Anthoxanthum monticola (Bigelow) Veldkamp subsp. monticola

. Awns of the upper staminate florets 4.57 mm long, attached at or above midlength, not or weakly geniculate, the lower portion not twisted or twisted with 12 gyres. 2n = 56, 58, 63.

Anthoxanthum monticola subsp. monticola grows from Greenland through Labrador to the eastern side of Hudson Bay and south to northern New Englan. It usually grows in similar but wetter and more exposed habitats than those occupied by subsp. alpinum.

Anthoxanthum arcticum Veldkamp

Arctic Sweetgrass; Hiérochloë pauciflore

Plants perennial; loosely cespitose or the culms solitary; rhizomes elongate, 0.3–1 mm thick. Culms 5–26(35) cm tall. Sheaths glabrous; ligules 0.4–1.3 mm long, obtuse; blades 2–25 cm long, 0.7–2 mm in diameter when rolled, involute to convolute, abaxial surfae glabrous, adaxial surface pubescent. Panicles 1–3(4.5) cm long, 0.3–0.5 cm wide, spikelike, with 1–2 spikelets per branch. Spikelets 3.5–5 mm long, green to purple; rachilla internodes about 0.1 mm long, glabrous. Glumes subequal, 2.9–4.7 mm long, shiny; lowest 2 florets staminate; lemmas sparsely hairy, acute or slightly notched, unawned or awned, awns to 1 mm long; bisexual lemma 2.9–4.4 mm long, with sparse, spreading hairs towards the tips; anthers 1.5–3 mm long. Caryopses about 2.5 long. 2n = 28.

Anthoxanum arcticum is a circumpolar coastal and lowland species that is present in Alaska, Canada, and Russia but not Greenland. It usually grows in wet tundra on acidic, peaty souls. In the warmest sections of the western high arctic, it is customarily rooted in mats of moss that are growing over carbonate substrates.

Anthoxanthum occidentale (Buckley) Veldkamp

California Sweetgrass

Plants perennial; loosely cespitose or the culms solitary; rhizomes elongate, 1–3 mm thick. Culms (40)60–90 cm tall. Sheaths scabrous to scabridulous; ligules 1.5–4(6) mm long, rounded to truncate; blades 20–40 cm long, (3)5–15 mm wide, flat, rather stiffly erect, narrowing to the base, glabrous, often glacuous, veins widely spaced, abaxial surface with evident cross-venation; flag leaf blades 3.5–10 cm long. Panicles 8–13 cm long, (1)2–6 cm wide, diffuse, with slender, often drooping braches and 3+ spikelets per branch. Spikelets 4.5–6 mm long. tawny or green to olive-green, sometimes infused with purple; rachilla internodes 0.2–0.5 mm long, glabrous. Glumes subequal, equaling or slightly exceeded by the tops of the bisexual florets; lower glume 4.5–5 mm long, 0.76–1 mm wide; upper glume 3.5–5.2 mm long, 1–1.8 mm wide. Lowest 2 florets staminate; lemmas usually mostly glabrous on the body, sometimes with scattered hairs, margins usually pilose, tops scabridulous, rounded, and shallowly bilobed, unawned or awned, awns to 1 mm long; first lemma 4–5 mm long, 0.75–1 mm wide, narrowly elliptic, length more than 5 times the width; bisexual floret 3.5–4.5 mm long, lemma marginspilose, particularly distally; anthers 2–3.5 mm long. 2n = 42.

Anthoxanthum occidentale grows in moist to fairly dry forested areas from Klickitat County, Washington, south to the coastal mountains of San Luis Obispo County, California. Its long flag leaves and more elongate spikelet parts make it easier to distinguish from A. hirtum than the key suggests.

Anthoxanthum nitens (Weber) Y. Schouten & Veldkamp

Vanilla Sweetgrass; Holy Grass; Hiérochloë odorante; Foind’Odeur; Herbe Sainte

Plants perennial; loosely cespitose or the culms colitary; rhizomes elongate, 0.7–2 mm thick. Culms (5)15–50(90) cm tall. Sheaths brownish or reddish, glabrous or puberulent; ligules 0.5–6.5(8) mm long, truncate, obtuse, or acute; blades of basal and cauline leaves 10–30 cm long, 2–8 mm wide, usually flat, sometimes inrolled, abaxial surface glabrous or puberulent, without prominent cross venations, adaxial surface glabrous; flag leaf blades 0.3–1.5(4.5) cm long, 1.5–4.5(6) mm wide. Panicles (2)4–9(12.5) cm long, (1.5)2–5(7) cm wide, open, pyramidal, with 8–100 spikelets; branches with 3+ spikelets. Spikelets (2.5)3.–7.5 mm long, mostly tawny, sometimes tinged with green; rachilla internodes 0.15–0.3 mm long, glabrous. Glumes subsequal, exceeding the florets, glabrous; lowest glume in each spikelet with length 2–5 times its width, usually shorter and wider than the upper glume. Lowest 2 florets: staminate; lemmas hairy, particularly distally, hairs brown, often papillose-based, to 0.8 mm long on the margins and to 0.3 mm long near the tips, margins with 11–26 hairs per mm, midvein usually terminating at the tops or extending beyond as an awn, tips acute to rounded, entire or bifid, unawned, mucronate or with a thin awn up to 0.5 mm long; lowest lemma 3.4–5 mm long, 1–1.5 mm wide, length usually less than 4 times width; bisexual florets: lemmas 2.5–4 mm long, usually hairy distally, hairs 0.1–0.5 mm long, appressed or almost so at mautiry, longer, divergent hairs, if present, concentrated near the midvein; anthers of staminate florets 0.9–2.3 mm long, those of the bisexual floret 1.2–1.6 mm long. 2n = 28, 42.

Anthoxanthum nitens [= Hierochloë odorata (L.) P. Beauv.] is primarily a European species. In North America, it grows along the eastern coast rom Labrador to New England, It is not known from Greenland although it grows in both Iceland and northwestern Europe. It is found in wet meadows and at the edges of sloughs, marshes, roadsides, and fields. Only A. nitens (Weber) Y. Schouten & Veldkamp subsp. nitens grows in North America; it is also present in Europe. It differs from A. nitens subsp. balticum (G. Weim.) G.C. Tucker in beings almost always awned and in being tetraploid with 2n = 28.

North American taxonomists have generally treated A. hirtum and A. nitens as a single species, A. hirtum (or, more often, as Hierochloë odorata). The two are distinct, although not easy to distinguish. Weimarck (1973) separate d the two based on the density of the lateral hairs and development of the awns of the staminate florets. The distribution and length of hairs on the tips of the bisexual florets was found to be more reliable when preparing this account. M.J. Harvey (pers. comm.), who treated the two as a single species, noted that plants from the Maritime Provinces collected near salt water were uniformly 2n = 28 whereas those from the interior of New Brunswick and westward had 2n = 56. This observation is consistent with Weimark’s chromosome counts and distribution maps.

Anthoxanthum hirtum (Schrank.) Y. Schouten & Veldkamp

Hairy sweetgrass; hairy holygrass.

Plants perennial; loosely cespitose or the culms solitary; rhizomes elongate 0.7–2 mm thick. Culms 40–85 (110) cm tall. Sheaths brownish or reddish; ligules 2.5–5.5 mm long; blades of basal and cauline leaves 2.5–5.5 mm wide, abaxial surface glabrous and shiny, adaxial surface pilose; blade of flag leaf 1–4.5 (6) cm long, 3–4.5 mm wide. Panicles (5)7–.5–15 cm long, 2–10 cm wide, open, pyramidal, with 20–100+ spikelets; branches with 3+ spikelets. Spikelets 4–6.3 mm long, tawny at maturity; rachilla internodes 0.1–0.3 mm long. Glumes subequal, exceeding the florets, glabrous, often somewhat purplish; lowest 2 florets staminate; lowest 2 lemmas 3–5 mm long, with hairs to 0.5 mm long towards their tips, margins with 16–30 hairs per mm, hairs 0.5–1 mm long, lemma tips acute, emarginated or bifid; lowest lemma 3–5 mm long, 1.1–1.3 mm wide, length usually less than 4 times its width, elliptic, awned, awns 0.1–1.1 mm long; bisexual lemma 2.9–3.5 mm long, hairy distally, the hairs 0.5–1 mm long, evenly distributed around the tops, their bases strongly divergent from the lemma surface; anthers of staminate florets 1.6–2.1 mm long, those of the bisexual florets 1.2–1.3 mm long. 2n = 56.

Anthoxanthum hirtum is the most widely distributed species of Anthoxanthum in North America, extending from Alaska to northeastern Quebec and south to Washington, Colorado, South Dakota, Illinois, Ohio, and New York. It is not known from Newfoundland or Greenland. Outside North America it extends from Scandinavia south to Germany and east to Asiatic Russia. It grows in wet meadows and marshes with sweet, not salty or brackish, water.Because much of its native habitat has been drained, it is becoming less common. It does not grow well from seed.

Its short flag leaf and more circular spikelets distinguish it from A. occidentale. The relative abundance and even distribution of hairs longer than 0.5 mm on the bisexual lemma distinguish it from A. nitens.

Weimark (1971, 1987) has recognized three subspecies in A. hirtum, which he treated as Hierochloë hirta. He stated that only subsp. arctica grew in North America but several North American specimens seem to fit within his circumscription of H. hirta subsp. hirta. Because the variation between the two appears continuous, North American plants are regarded here as belonging to A. hirtum (Schrank.) Y. Schouten & Veldkamp subsp. hirtum