13.02 EREMOPYRUM (Ledeb.) Jaub. & Spach
Signe Frederiksen

Plants annual. Culms 3–40 cm, geniculate. Sheaths open for most of their length; auricles present, often inconspicuous; ligules 0.4–2 mm, membranous, truncate; blades 1–6 mm wide, flat, linear. Inflorescences distichous spikes, 0.8–4.5 cm, with 1 spikelet per node, usually erect when mature; rachis internodes flat, margins glabrous or with hairs, hairs white; middle internodes 0.5–3 mm; disarticulation in the rachises, at the nodes beneath each spikelet, or at the base of each floret. Spikelets 6–25 mm, including the awns, more than 3 times the length of the internodes, divergent, laterally compressed, with 2–5 bisexual florets, sterile florets distal or absent. Glumes equal, 4–19 mm, including the awns, coriaceous, becoming indurate, 1-keeled initially, sometimes 2-keeled at maturity, keels glabrous or hairy, never with tufts of hair, bases slightly connate, apices tapering to a sharp point or straight awn; lemmas 5–24 mm, coriaceous, rounded basally, keeled distally, 5-veined, unawned or shortly awned; paleas usually shorter and thinner than the lemmas, 2-keeled, ciliate or scabrous distally, keels sometimes prolonged into 2 toothlike appendages; anthers 3, 0.4–1.3 mm, yellow. Ovaries pubescent; styles 2, free to the base. x = 7. Haplomes F, Xe. Name from the Greek eremia, ‘desert’, and pyros, ‘wheat’.

Eremopyrum includes 5–10 species that grow in steppes and semidesert regions from Turkey to central Asia and Pakistan. Three species have been found in North America; only E. triticeum is widepsread. In their native ranges, species of Eremopyrum are valuable fodder on ephemeral spring pastures.

SELECTED REFERENCES Frederiksen, S. 1991. Taxonomic studies in Eremopyrum (Poaceae). Nordic J. Bot. 11:271–285; Melderis, A. 1985. Eremopyrum (Ledeb.) Jaub. & Spach. Pp. 227–231 in P.H. Davis (ed.). Flora of Turkey and the East Aegean Islands, vol. 9. University Press, Edinburgh, Scotland. 724 pp.; Sakamoto, S. 1979. Genetic relationships among four species of the genus Eremopyrum in the tribe Triticeae, Gramineae. Mem. Coll. Agric. Kyoto Univ. 114:1–27.

For an interactive dichotomous key, click here; for an interactive, multientry key, click here.

1. Glumes 1-veined and 2-keeled at maturity; lemmas of the first floret in each spikelet pubescent on the lower 1/2, glabrous distally, the other lemmas glabrous; disarticulation beneath the florets, sometimes at the base of the spikes ... E. triticeum
1. Glumes usually 3–5-veined and 1-keeled; lemmas of all florets alike in their pubescence or lack thereof; disarticulation at the rachis nodes ... 2
2. Glume bases straight; spikes 1.3–2.8 cm wide ... E. bonaepartis
2. Glume bases arcuately curved; spikes 0.9–1.8 cm wide ... E. orientale

1. Eremopyrum triticeum (Gaertn.) Nevski
Annual Wheatgrass

Culms to 30 cm, mostly glab-rous, puberulent below the spikes. Sheaths of upper leaves inflated; blades 1–3(6) mm wide, scabrous or shortly pilose distally. Spikes 1.3–2.4 cm long, 0.8–2 cm wide, elliptic, ovate, or nearly circular in outline; disarticulation beneath each floret, sometimes at the base of the spikes, not in the rachises. Spikelets 6–12 mm, with 2–3 florets. Glumes 4–7.5 mm, glabrous, 1-veined and -keeled, becoming 2-keeled by the development of a ridge adjacent to the vein, bases prominently inflated and curved; lemmas 5–7.5 mm, prominently keeled towards the subulate apices, lowest lemma in each spikelet pubescent on the proximal 1/2, hairs 0.1–0.15 mm, glabrous distally, the other lemmas glabrous; palea keels not prolonged. 2n = 14.

Eremopyrum triticeum is known primarily from scattered disturbed sites in western North America, from southern Canada to Arizona and New Mexico. Like most weeds, it is probably more widely distributed than herbarium records indicate. It is tolerant of alkaline soils, and is summer-dormant.

2. Eremopyrum bonaepartis (Spreng.) Nevski

Culms to 30 cm, smooth, most-ly glabrous, puberulent below the spikes. Blades 3–5 mm wide, scabrous distally. Spikes 1.4–4.5 cm long, 1.3–2.8 cm wide, oblong, obtuse, or trun-cate; disarticulation at the rachis nodes. Spikelets 10–25 mm, with 3–5 florets. Glumes 4–19 mm, scabrous or hairy, 3–5-veined, 1-keeled, lateral veins obscure, bases straight; lemmas 6–24 mm, glabrous, scabrous, or hirsute, all alike in their pubescence, apices subacute to shortly awned; palea keels prolonged into 2 toothlike appendages. 2n = 14, 28.

In the Flora region, Eremopyrum bonaepartis is known only from a few collections in Arizona. Several infraspecific taxa have been recognized in Eurasia: subsp. bonaepartis has glabrous lemmas and glumes; specimens with pilose, hirsute, or fairly scabrous lemmas and glumes have been referred to as subsp. hirsutum (Bertol.) Melderis or subsp. sublanuginosum (Drobow) Á. Löve; and those with awned lemmas have been called subsp. turkestanicum (Gand.) Tzvelev. No attempt has been made to determine which are present in the Flora region.

3. Eremopyrum orientale (L.) Jaub. & Spach

Culms to 15 cm, smooth, mostly glabrous, puberulent below the spikes. Sheaths of upper leaves often somewhat inflated; blades 2–3 mm wide, more or less scabrous on both surfaces. Spikes 1.3–3.5 cm long, 0.9–1.8 cm wide, usually ovate-elliptic; disarticulation at the rachis nodes. Spikelets 7–12 mm long, with 2–3 florets. Glumes 5–12 mm, lanceolate, 3–5-veined, 1-keeled, lateral 2–3 veins prominent, hispid, bases curved, apices gradually tapering to a 0.5–3 mm awn; lemmas 5–12 mm, hispid, hairs 0.5–2 mm, prominently keeled, awned, awns 0.5–4 mm; paleas pubescent between the keels, keels prolonged into 2 toothlike appendages. 2n = 28.

Eremopyrum orientale has been collected from southern Manitoba, growing with E. triticeum, and has been reported from southeastern British Columbia and New York. It is not known to be established in the Flora region.