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

French: aira caryophyllée, canche caryophyllée 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. (2011)
Chile (continental) Chile	Chile (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 12)
China China	China (People's Republic of)		Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2011) Dry grassy places in mountains; ca. 3600 m. W. Xizang.
Japan Japan	Japan (country)	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".

Control: 

Physical:  Small patches may be dug out.

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

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

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

Taxonomic information about Aira caryophyllea 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.

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.

Edgar, E./Connor, H. 2000. Flora of New Zealand, vol. V: Gramineae. Manaaki Whenua Press. .

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.

Lorence, David H./Flynn, Tim. 1997. New naturalized plant records for Kaua‘i. In: Evenhuis, Neal L. and Miller, Scott, E., eds. Records of the Hawaii Biological Survey for 1996. Part 2: Notes. Bishop Museum Occasional Papers. 49:9-13.

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.

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

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.

Wood, K. R. 2006. New plant records and rediscoveries within the Hawaiian Islands. In: Evenhuis, Neal L. and Eldredge, Lucias G., eds. Records of the Hawaii Biological Survey for 2004-2005. Part 2: Notes. Bishop Museum Occasional Papers 88:15-19.

Zhengyi, Wu/Raven, Peter H./Deyuan, Hong. 2011. Flora of China (online resource).