13.04 TAENIATHERUM Nevski
Plants annual. Culms (5)10–55(70) cm, erect, glabrous; nodes 3–6. Leaves evenly distributed; sheaths open, usually glabrous; auricles 0.1–0.5 mm, rarely absent; ligules membranous, truncate; blades flat to involute. Inflorescences spikes, erect; nodes 4–24(28), each with 2(3, 4) spikelets; internodes 0.5–3.5 mm. Spikelets with 2(3) florets, the lowest floret in each spikelet bisexual, the distal floret(s) highly reduced, sterile; disarticulation above the glumes. Glumes 5–80 mm, equal, awnlike, erect to spreading or reflexed, bases connate. Bisexual florets: lemmas 5-veined, glabrous or scabrous, margins flat, scabrous, apices terminally awned, awns 20–110 mm, longer than the lemmas, divergent, often cernuous; paleas as long as the lemmas, keels antrorsely ciliate, apices truncate; lodicules 2, lobed, ciliate. Reduced florets: lemmas 3-veined, awned; paleas absent; anthers 3, yellow to purple. Caryopses narrowly elliptic, with an adaxial groove, apices pubescent. x = 7. Haplome Ta. Name from the Greek taenia, ‘ribbon’, and ather, ‘awn’.
Taeniatherum includes only one species. It is native to Eurasia.
SELECTED REFERENCES Frederiksen, S. 1986. Revision of Taeniatherum (Poaceae). Nordic J. Bot. 6:389–397; Humphries, C.J. 1978. Variation in Taeniatherum caput-medusae (L.) Nevski. Bot. J. Linn. Soc. 76:340–344.
1. Taeniatherum caput-medusae (L.) Nevski
Culms (5)10–55(70) cm. Aur-icles 0.1–0.5 mm, rarely absent; ligules 0.2–0.6 mm; blades (0.2) 0.7–2.5 mm wide, flat to invol-ute. Spikes 1.2–6 cm. Spikelets 6–45 mm; glumes (5)7–80 mm, awnlike, erect to reflexed. Bi-sexual florets: lemmas 5.5–8 mm, awns (20) 30–110 mm, divergent; anthers 0.8–1 mm. Caryopses 4–5.2 mm. 2n = 14.
Taeniatherum caput-medusae is native from Portugal and Morocco east to Kyrgyzstan. It usually grows on stony soils, and flowers from May–June (July). It is an aggressive invader of disturbed sites in the western United States, where it has become a serious problem on rangelands. It has been found as a rare introduction at several sites in the eastern United States, but may not persist there. It is listed as a noxious weed by the U.S. Department of Agriculture.
Frederiksen (1986) recognized three subspecies within Taeniatherum caput-medusae, distinguishing among them on the basis of morphology and geography. Plants in the Flora region belong to Taeniatherum caput-medusae (L.) Nevski subsp. caput-medusae. It differs from the other two subspecies in its longer glumes and shorter lemmas.