Achnatherum hymenoides (Roemer & J.A. Schultes) Barkworth

by Bala Chaudhary, Native Plants Class 2003
Common names
: Indian ricegrass, sand grass, Indian millet
Family: Poaceae
Synonymy: Eriocoma cupidata Nutt., Oryzopsis hymenoides (Roemer & J.A. Schultes) Ricker ex Piper, and Stipa hymenoides Roemer & J.A. Schultes.
Etymology: The previous genus name, Oryzopsis comes from Greek, meaning “rice like”. Hymenoides means membranous. (1)

Identification
Growth form:
Dense bunchgrass reaching 30-70 cm in height. (2, 4).
Roots:
Sheath: Leaf sheaths can be hairless or covered with scales and rough to the touch. They are round, split, prominently veined, usually with a fringe of hairs at throat. The base of leaf sheaths is often purple (2, 4).
Leaves: Leaf blades are firm, narrow (5mm), and nearly as long as the stems; margins are typically involute, or rolled inward (2, 4).
Ligules: Ligules have tufts of hair on either side and are 3-8 mm long on the main stem leaves. (2)
Inflorescence: Inflorescence is a diffuse panicle, 5-15 cm long and nearly as broad. It branches dichotomously and the branchlets and pedicels spread divaricately. The pedicels, diagnostically thin and kinked, are 1-2 cm long. Spikelets are 6 to 10 mm long and contain a single flower (2,4).
Glumes: The glumes are acuminate (form a tip at the end) or short-aristate (have short bristles) and are 5-8 mm long. They can be hairless, scaly, or finely pubescent. They also have three deep nerves running lengthwise (2, 4).
Lemma: The lemma is 3 to 5 mm long and covered with soft shaggy unmatted hairs 2-4 mm long (X). It appears dark brown to black at maturity (2, 4).
Awn: The awn is 3-6mm long, stout, and can be slightly twisted (2, 4).
Caryopsis: The seed is plump, dark-colored, rice-like, and can be up to 2mm (4).
Similar species: Thirteen other species of Achnatherum can be found in Arizona. Achnatherum hymenoides can be distinguished from the others by its long spikelet (6-10 mm), presence of hairs on the lemma, and large diffuse panicle. (5)

Ecology
Life history:
Perennial grass
Native/introduced: Native (6).
Photosynthetic pathway: C3 (6)
Phenology: Indian ricegrass flowers from May to August (2, 4).
Distribution: Indian ricegrass grows in dry, open, sandy soils of desert scrub, sagebrush shrubland, and pinyon-juniper woodland. It grows at elevations between 3500 and 6500ft and is found in Arizona in Apache, Navajo, Coconino, Mohave, Yavapai, and Pima Counties. It is a widely distributed grass in western North America and can be found from Manitoba to British Columbia, south to Texas, California and northern Mexico (2, 4).

Uses

Native Americans used Indian ricegrass as a food grain. It was also cut for hay and can be a good forage grass.

References
1. Gledhill, D. 1989. The Names of Plants. Cambridge University Press. New York, NY.

2. Gould, F. 1988. Grasses of the Southwestern United States. University of Arizona Press. Tucson, AZ.

3. Hickman, J.C. 1993. The Jepson Manual: Higher Plants of California. University of California Press. Berkeley, CA.

4. Hitchcock, A.S. 1971. Manual of the Grasses of the United States. Dover Publishing. New York, NY.

5. Kearney T.H. and Peebles R.H. 1960. Arizona Flora. University of California Press. Berkeley, CA.

6. USDA, NRCS. 2002. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.