Hordeum murinum L., Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: bulbous barley, false barley, mouse barley, wall barley

French: orge des rats, orge queue de souris

Japanese: mugi-kusa

Spanish: cebada ratonera, cebadilla, cola de zorro, espigadilla

Habit:  grass

Description:  "Habit: Annual; caespitose. Culms 6-60 cm long; 3-5-noded. Leaf-sheath oral hairs lacking. Leaf-sheath auricles falcate. Ligule an eciliate membrane; 0.5-1 mm long. Leaf-blades 2-20 cm long; 2-8 mm wide. Inflorescence composed of racemes. Racemes 1; single; linear, or oblong; bilateral; 4-12 cm long. Rhachis fragile at the nodes; flattened. Spikelet packing broadside to rhachis. Rhachis internodes oblong; 3-3.5 mm long; falling with spikelet above. Spikelets in threes. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 2 in the cluster. Pedicels oblong. Sterile spikelets: Companion sterile spikelets well-developed; containing empty lemmas, or male; lanceolate; dorsally compressed; 7-11 mm long; as long as fertile; deciduous with the fertile. Companion sterile spikelet glumes subulate; 16-30 mm long; eciliate on margins, or ciliate on margins. Companion sterile spikelet lemmas 1; exserted from glumes; 7-11 mm long; 1-awned; with 10-40 mm long awn. Fertile spikelets: Spikelets comprising 1 fertile florets; without rhachilla extension. Spikelets lanceolate; dorsally compressed; 7-12 mm long; falling entire; deciduous with accessory branch structures. Glumes: Glumes collateral; similar; gaping. Lower glume subulate; 25-30 mm long; 1 times length of upper glume. Lower glume margins ciliate. Upper glume subulate; 25-30 mm long. Upper glume margins ciliate. Florets: Fertile lemma lanceolate; 7-12 mm long; coriaceous; without keel; 5 -veined. Lemma surface scabrous; rough above. Lemma apex acuminate; awned; 1 -awned. Principal lemma awn 18-50 mm long overall; limb scabrous. Flower: Anthers 3; 0.7-1.2 mm long. Ovary pubescent on apex. Fruit: Caryopsis with adherent pericarp; ellipsoid; sulcate on hilar side; hairy at apex. Embryo 0.2 times length of caryopsis. Hilum linear; 1 times length of caryopsis"  (World Grass Species).

subspecies leporinum Link:  "Pale green annuals; culms geniculate to erect, (1-) 2-4 (-6) dm tall.  Sheaths glabrous or sometimes pilose; ligule 0.5-1 mm long, truncate, erose, ciliolate; blades flat, 2-5 mm wide, glabrous to pilose, auricles well-developed, up to 3.5 mm long.  Inflorescences composed of erect spikes 4-7 (-10) cm long (excluding awns), ± partially enclosed by the sheath, rachis readily disarticulating, the segments (1.5-) 2-3 mm long; spikelets well-developed, the central spikelet sessile, rachilla joints 1-2 mm long, equaling or exceeding pedicels of lateral spikelets, the lateral spikelets usually staminate; glumes 15-22 (-28) mm long, those of the central spikelet and the second glume of the lateral spikelet narrowly lanceolate, 3-nerved, the nerves scabrous, margins ciliate, the first glume of the lateral spikelet awn-like and somewhat longer than glumes of the central floret, scabrous; lemma of central spikelet (6-) 7-9 mm long, glabrous, 5-nerved, the nerves faint, lemmas of lateral spikelets somewhat larger than those of central floret, 7-10 mm long, sterile, lemmas of all spikelets tapering to awns 18-30 mm long; palea lanceolate, 11-12 mm long, 2-nerved, long-pilose and membranous between the nerves and at the margins, folded, evenly appressed long-pilose, apex obtuse to rounded.  Caryopsis reddish brown, oblong, 3-4 cm long, apex densely reddish brown long-pubescent"  (Wagner et al., 1999; p. 1552).

Habitat/ecology:  "Deserts and desert scrub, arid grassland.  A native of dry grassland and disturbed places with three subspecies within the native range.  The grass is invasive because it forms dense swards that displace native grasses and forbs by competing for water, nutrients and space.  The grass is highly competitive to native annuals in arid areas"  (Weber, 2003; p. 203).

In Hawai‘i, "naturalized in moderately moist places such as pastures and abandoned fields, (0-) 30-2,440 m"  (Wagner et al., 1999; p. 1552).

Propagation:  Seed

Native range:  Native to Europe, naturalized in North America  (Wagner et al., 1999; p. 1552).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Pacific offshore islands) Lord Howe Island	Lord Howe Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 23) Subsp. glaucum (Steud.) Tzvelev. "An introduced weed". Voucher cited: L.M. Bingley 27 (K). Subsp. leporinum (Link) Arcang. Voucher cited: A.C. Beauglehole 5433 (CANB, MEL)
Australia (Pacific offshore islands) Norfolk Islands	Norfolk Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 12) Subsp. glaucum (Steud.) Tzvelev. "An introduced weed". Vouchers cited: 1962, P. Ralston (CHR); W.R. Sykes NI 76 (CHR). Subsp. leporinum (Link) Arcang. Vouchers cited: F.C. Allen (CHR), 135 F.C. Allen 221 (CHR)
Chile (offshore islands) Rapa Nui (Easter) Island	Rapa Nui (Easter) Island (Isla de Pasqua)	introduced	Skottsberg, Carl (1953) (p. 80)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced	Skottsberg, Carl (1953) (p. 216)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced	Skottsberg, Carl (1953) (p. 216) Coast and mountains.
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced	Skottsberg, Carl (1953) (p. 216)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
Chile (offshore islands) Juan Fernández Islands	Morro El Verdugo	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
Chile (offshore islands) Juan Fernández Islands	Morro Juanango	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1552) ssp. leporinum Link; voucher cited: Rock 3198 (BISH)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1552) ssp. leporinum Link
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1552) ssp. leporinum Link
Philippines Philippine Islands	Philippine Islands		Hafliger, Ernst/Scholz, Hildemar (1980) (p. 87)
United States (other Pacific offshore islands) Midway Atoll	Midway Atoll	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1552) ssp. leporinum Link

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Chile (continental) Chile	Chile (Republic of)		Hafliger, Ernst/Scholz, Hildemar (1980) (p. 87)
Japan Japan	Japan (country)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 184)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 192)

Control: 

Physical:  Hand pull scattered plants.

Chemical:  Spray with a grass-selective herbicide (Weber, 2003; p. 203).

Additional information:
Additional online information about Hordeum murinum is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Hordeum murinum as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Hordeum murinum may be available from the Germplasm Resources Information Network (GRIN).

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Clayton, W.D./Harman, K.T./Williamson, H. 2011. World Grass Species: Descriptions, Identification, and Information Retrieval [GrassBase - The Online World Grass Flora]. The Board of Trustees, Royal Botanic Gardens, Kew.

Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido. 2006. Nouveau catalogue de la flore vaculaire de l'archipel Juan Fernández (Chile) [Nuevo catálogo de la flora vacular del Archipélago Juan Fernández (Chile)]. Acta Bot. Gallica 153(4):399-587.

Hafliger, Ernst/Scholz, Hildemar. 1980. Grass weeds, vol. 2. CIBA-GEIGY Ltd., Basle, Switzerland. 137 pp. + plates.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

Orchard, Anthony E., ed. 1994. Flora of Australia. Vol. 49, Oceanic islands 1. Australian Government Publishing Service, Canberra.

Skottsberg, Carl. 1953. The natural history of Juan Fernandez and Easter Island. Vol. II, Botany. Almqvist &l; Wiksells, Uppsala. 960 pp.

U. S. Government. 2011. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.