Hierochloë odorata (L.) (Beauv. Sweet Grass)

English Common Names

Sweet grass, sweetgrass, sweet holygrass, Indian sweet grass, vanilla grass, seneca grass.

The name "sweet grass" is mostly used for species of Hierochloë, but is sometimes applied to other species, such as Glyceria septentrionalis Hitchc.

French Common Names

Foin d'odeur, herbe sainte.

In French, "foin d'odeur" is also applied to the introduced grass Anthoxanthum odoratum L.

Morphology

Sweet grass is a semi-erect perennial, the open panicles reaching heights of (10-)25-60(-100) cm. The creeping rhizomes are slender, and numerous, and shallow feeding roots arise from these as well as the base of the culm. Shiny green vegetative blades, (2-)3-6(-8) mm wide, 20-80 cm long, originate individually from the rhizomes (a form named H. nashii Kaczmarek is reputed to produce especially long leaf blades).

Sweet grass is notable for its very early flowering, very shortly after spring growth begins. This is possible because the buds for the inflorescences were developed in the preceding autumn. Seeds are ripe in early summer, but seed set is sometimes low or absent, and some colonies produce seeds through apomixis rather than sexually.

Often confused with sweet grass, the European sweet vernal grass (Anthoxanthum odoratum) also has a vanilla-like fragrance but differs in its softly hairy foliage and spike-like inflorescence.

Classification and Geography

Hierochloë odorata is sometimes included in other genera, notably Savastana or Torresia.

Sweet grass is a rather variable polyploid complex, with diploids (with 14 chromosomes), tetraploids (28 chromosomes), octoploids (56 chromosomes), and other cytological phenomena. Some of the chromosome races have been recognized as separate species.

Recent taxonomic study has alleged that there are two very similar species in North America: H. odorata ssp. odorata in eastern coastal North America (Labrador to New Jersey), and H. hirta (Schrank) Borbás ssp. arctica G. Weim. in most of northern North America (north of 40° excepting eastern Northwest Territories, Nunavut and the arctic islands). However, the two taxa are difficult to separate and they are best placed together under the name H. odorata, pending additional study.

Ecology

Sweet grass is typically found in prairies, moist meadows, or along shorelines, and also in salt marshes, mostly among other herbs and shrubs. In eastern Canada it is spreading along roadsides receiving runoff with deicing salt.

Medicinal Uses

Sweet grass infusions were used by Plains Indians to treat various ailments, including coughs and sore throats, venereal infections, bleeding after childbirth, chapped or wind-burned skin, and eye irritations. However, the principal medical value of sweet grass is as a spiritually healing plant.

Indigenous Peoples have long considered sweet grass to be one of the most important of sacred plants (others are the sages, cedar, alpine fir, juniper, tobacco, and corn). This was the most common sacred plant of Plains Indians, who occupied the region between the Mississippi and the Rockies in the US, and from the Rockies to Manitoba in southern Canada. Sweet grass is a regular component of "medicine pouches," which are typically hung about the neck, the wearer symbolically asking for spiritual protection. Elders often have the responsibility of providing the plants for medicine pouches, and may be given sweet grass as a sign of respect.

The plant is, in fact, symbolic of Native spirituality, a tribute to the Creator or Great Spirit, and an aid to alleviating or removing evil spirits. Sweet grass is frequently braided and burned, customarily in the morning or evening, both in individual and group ceremonies, particularly at pow wows and celebrations.

The plant is also burned in an incense (alone or in a mixture) to produce a sacred smoke, the smouldering material passed from person to person as a purification rite and as a symbol of unity. Elders may also conduct a pipe ceremony, in which tobacco (commercial or other plants) is smoked while passing around a smouldering braid of sweet grass. The grass braid requires regular fanning to stay lit.

Toxicity

Coumarin in sweet grass is a flavouring agent (e.g., in the culinary herb sweet woodruff, Galium odoratum (L.) Scop.), but is toxic, known in experimental animals to cause liver damage, retard growth, and cause cancer and testicular atrophy. Foraging cattle are believed to have shown toxic reactions to eating large amounts of coumarin-containing plants.

In the US coumarin is approved for use as a flavouring agent in alcoholic beverages, but is no longer allowed in food. Since humans do not orally consume much sweet grass, its toxic potential is not of importance. Concern does not seem to be recorded for potential toxicity for livestock.

Chemistry

The odour of sweet grass is due to coumarin.

Non-medicinal Uses

Sweet grass is widely used in weaving and basketwork by Native Americans. The leaves of the flowering stalk are too short to be of value. The long vegetative leaves are individually harvested by native people from the middle of July until September, mid-season considered as supplying the best material. The dried leaves are strong and flexible and are often used to prepare handicrafts, largely for the tourist trade. The pleasantly flavoured baskets, bowls, trays, and mats are a unique traditional product of Native Peoples, although it may be noted that sweet grass handiwork sold by Indian tribes outside of the distribution range of H. odorata may well have been manufactured from other species locally called sweet grass.

In southern Quebec, the introduced sweet vernal grass, Anthoxanthum odoratum, has also been used by native peoples for basketwork. Cultivated H. odorata may produce larger, superior leaves for weaving than wild-growing plants. Some native handicrafts are threatened by recent urbanization and habitat destruction, since this eliminates or reduces the required plant materials.

The essential oil of sweet grass is used in perfumes. The dried leaves have been employed to scent pillows and clothing. On drying, the vanilla fragrance, due to coumarin, becomes more evident. The odor may not be apparent in fresh plants. When properly cured, sweet grass remains pleasantly scented for up to 3 years (some say the scent lasts indefinitely).

The coumarin content results in bitterness, which has been suspected of discouraging its use as forage by cattle. Although sweet grass is not as palatable as most grasses, it will nevertheless be eaten fairly readily by cattle, and does not transmit its odour to milk. Certainly some humans seem to like the taste. Leaves have been placed in bottles of vodka as a flavorant, and packets of grass have been sold in the US for this purpose. Extract from the plant has been used in Europe to flavour candy, soft drinks, and tobacco.

The aggressively creeping rhizomes of sweet grass are very desirable for stabilizing soil. The tolerance of the species to wet areas makes it especially valuable in controlling erosion by water. The limited height of the plant may be advantageous where appearance is important, since tall-growing herbs often need mowing.

Propagating sweet grass as a soil stabilizer is difficult by seed, since so little is produced, and there has been experimentation to establish the plant by rhizomes (underground creeping stems) or stolons (above-ground creeping stems). Experience to date suggests that this species may be one of the best soil stabilizers of moist and moderately saline sites such as road verges. Advantages of vegetative propagation include avoidance of seed shattering and ease of establishment.

Agricultural and Commercial Aspects

There is potential for increased cultivation of sweet grass in support of native culture and handicraft production, as well as for use in soil stabilization. The plant is best raised in a fertile soil enriched with humus, in a moist to wet site. It can be grown in full sun or partial shade. One authority recommended adding a little salt (NaCl) to the soil, since the species is found on the margins of saline as well as fresh water. Plantings may quickly develop into large patches by rhizome reproduction. A one inch plug can develop to a dense 10 square foot mass in 1 year and cover over 50 square feet in 2 years.

Myths, Legends, Tales, Folklore, and Interesting Facts

Aromatic herbs have been used for sacred objectives for millennia, so it is not surprising that Christians in Europe and Native Peoples of North America independently adopted sweet grass for religious purposes.

Selected References

• Dore, W.G., and McNeill, J. 1980. Grasses of Ontario. Agricult. Can. Res. Br. Monogr. 26. 566 pp.
  
  
• Dufault, R.J., Jackson, M., and Salvo, S.K. 1993. Sweetgrass: history, basketry, and constraints to industry growth. In New crops. Edited by J. Janick and J.E. Simon. Wiley, New York, NY. pp. 442-445. (N.B. the "sweet grass" referred to in this paper is Muhlenbergia filipes Curtis, not Hierochloe odorata.)
  
  
• English, M. 1982. Sweet grass -- a sacred herb. The Herbarist 48: 5-9.
  
  
• Ferris, C., Callow, R.S., and Gray, A.J. 1992. Mixed first and second division restitution in male meiosis of Hierochloe odorata (L.) Beauv. (holy grass). Heredity 69: 21-31.
  
  
• Fijalkowski, D., and Wawer, M. 1983. [1986]. Hierochloe R. Br. in the Lublin Macroregion (Poland). Ann. Univ. Mariae Curie-Sklodowska Sect. C Biol. 38(1-21): 109-118. [In Polish.]
  
  
• Fleurbec. 1985. Plantes sauvages du bord de la mer. Saint-Augustin (Portneuf), Québec. 286 pp.
  
  
• Hitchcock, A.S. (revised by A. Chase). 1951. Manual of the grassses of the U.S. U.S. Dep. Agricult. Misc. Publ. No. 200, 2nd ed. 1051 pp.
  
  
• Klebesadel, L.J. 1974. Sweet holygrass, a potentially valuable ally. Agroborealis (Inst. Agricult. Sci., Univ. Alaska) 6(1): 9-10.
  
  
• Looman, J. 1982. Prairie grasses identified and described by vegetative characters. Agricult. Can. Publ. 1413. 244 pp.
  
  
• Ueyama, Y., Arai, T., and Hashimoto, S. 1991. Volatile constituents of ethanol extracts of Hierochloe odorata var. pubescens Kryl. Flavour Fragrance J. 6(1): 63-68.
  
  
• Weimarck, G. 1971. Variation and taxonomy of Hierochloe (Gramineae) in the northern hemisphere. Bot. Not. 124: 129-175.
  
  
• Wierzchowska-Renke, K., and Sulma,T. 1974. Studies of the Hierochloe herb. Evaluation of commercial Herba Hierochloe raw material collected at the Zulawy plantation. Acta Pol. Pharm. 31: 233-239. [In Polish.]