Aira caryophyllea L., Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  yes

Risk assessment results:  Reject, score: 9 (Go to the risk assessment).

Common name(s): [more details]

Chinese: yin xu cao

English: silver hairgrass, silvery hair grass

French: aira caryophyllée, canche caryophyllée

Habit:  grass

Description:  "Annuals; culms solitary or few, sometimes numerous, forming large perennial clumps resulting from reseeding, 3-40 cm tall.  Sheaths glabrous, open to base; ligule membranous, triangular, 4-5 mm long, apex entire but becoming lacerate; blades filiform or subsetaceous, usually 1-5 cm long, up to 1 mm wide.  Inflorescences paniculate, loose, ovate to oblong, 1-12 cm long, the branches bare at base; spikelets 2, ca. 3 mm long, clustered toward tips of capillary branches, pedicels 0.7-3.5 times as long as the spikelet and pear-shaped at apex; glumes pale brown, chartaceous, ovate, 2.3-3.5 mm long, enclosing the florets, nerves ± prominent, surface lustrous, glabrous except sparsely scabrous along keel, apex acute, slightly erose; lemmas dark reddish brown, narrowly ovate, 2-2.5 mm long, short-scabrous, apex acuminate, 2-lobed, apical teeth setaceous, awn 3-4 mm long, slightly geniculate, inserted below midpoint on dorsal face, rarely absent, callus minutely bearded at lateral margins of floret; palea similar in color, vestiture, and texture to lemma, 1.5-2 mm long, apex acuminate, somewhat adnate to caryopsis.  Caryopsis 1-1.5 mm long, ca. 0.5 mm in diameter, weakly adnate to lemma and palea and remaining enclosed within them"  (Wagner et al., 1999; p. 1495).

Description from GrassBase.

Habitat/ecology:  "Coastal vegetation, heath- and woodland, riparian habitats, wetlands, rock outcrops.  In the native range, this grass is found in forests on sandy and generally acid soils that are not too nutrient-poor, in heaths, on rocks and dunes.  It is adapted to nutrient-poor habitats and grows in dense colonies, eliminating native vegetation and preventing the establishment of native plants" (Weber, 2003; p. 33).

In Hawai‘i, "naturalized in pastures and on lava, often near moist areas, and in subalpine shrubland, 1,050-2,440 m"  (Wagner et al., 1999; p. 1495).

Propagation:  Seed

Native range:  Europe, Africa and western Asia (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced	Skottsberg, Carl (1953) (p. 215) Rather common in the basal region, more so in the western part.
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. 550)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced	Skottsberg, Carl (1953) (p. 215)
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. 550)
Chile (offshore islands) Juan Fernández Islands	Morro Juanango	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 550)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1495)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Lorence, David H./Flynn, Tim (1997) (p. 11) Voucher cited: Flynn 5843 (PTBG)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1495)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1495) Voucher cited: Munro 374 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wood, K. R. (2006) (p. 18) Voucher cited: K. R. Wood & J. Lau 10636 (BISH, PTBG, US)

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. (2013) Naturalized
China China	China (People's Republic of)		Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Dry grassy places in mountains; ca. 3600 m. W. Xizang.
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 191)
Mexico Mexico	Mexico (United Mexican States)	introduced	Weber, Ewald (2003) (p. 33)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Edgar, E./Connor, H. (2000) (p. 294) "Usually in dry, stony, or sandy ground, or in disturbed sites; rarely in damp ground at swamp or lagoon margins; sea level to subalpine".
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (Oregon)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (California)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (Washington)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Canada Canada	Canada	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (continental except west coast) United States (other states)	United States (other states)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Alabama, Georgia, Mississippi, South Carolina, Virginia Naturalized

Control: 

Physical:  Small patches may be dug out.

Chemical:  Spray with grass-selective herbicides (Weber, 2003; p. 33).