Hyparrhenia rufa (Nees) Stapf, Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 7 (Go to the risk assessment)

Common name(s): [more details]

English: giant thatching grass, jaragua grass, thatch grass, thatching grass

French: herbe rouge

Hindi: jaragua

Spanish: yaragua

Habit:  grass

Description:  "Perennial or sometimes annual [grass]; culms densely tufted, forming large clumps 3-25 dm tall, nodes long-pilose. Sheaths sparsely long-pilose, the hairs white, appressed at base, upper sheaths glabrous but with margins ciliate and hairs readily deciduous; ligule a firm, brownish membrane, 1-2.5 mm long; blades flat, glabrous or upper surface hirsute, 30-60 cm long, 2-8 mm wide, narrowed at base. Inflorescences large, paniculate, with numerous branches, the branches lax or contracted, fasciculate, 5-80 cm long, spathes linear-lanceolate, becoming reddish and rolled around the peduncle, 3-5 cm long, sparsely to densely long-pilose, racemes dull yellow, sometimes red-tinged, (1.5-)2-2.5 cm long, with (7-)9-14 awns per raceme pair, the awns rarely reflexed, with 1 homogamous pair of spikelets at the base of the lowest or of both racemes, raceme-bases unequal, sometimes connate, the upper one 2-3.5(-4) mm long, glabrous, rarely with a few long hairs, the articulation with the peduncle apex glabrous; sessile spikelet (3-)3.5-4.5(-5) mm long, glabrous to pubescent, but usually sparsely covered with stiff red hairs, usually glossy; pedicellate spikelet acute or rarely mucronate, callus 0.2-0.8 mm long, short and rounded to cuneate, narrowly truncate; lemma slender, filiform, ca. 2 mm long, membranous, awn arising from bifid apex, strongly twisted, geniculate, pubescent; ellipsoid to ovoid, ca. 3 mm long" (Wagner et al., 1999; p. 1554).

Description from GrassBase.

Habitat/ecology:  "Grassland, savanna, disturbed sites.  This grass occurs as a native in seasonally flooded grassland and open woodland.  It is a drought tolerant species and withstands dry seasons of several months, seasonal burning but also temporary flooding.  It forms dense swards where invasive that displace native grasses and forbs, preventing the establishment of other species and transforming native savannas into species-pure stands"  (Weber, 2003; p. 207).  Dry to mesic roadsides, disturbed areas. May carry wildfire.

"Grows in sandy or loamy soil.  Found on disturbed ground and roadsides." (Smith, 2002; p. 75). In Fiji, "reported as escaped and naturalized, but apparently it is uncommon" (Smith, 1979; pp. 380-381). In Hawai‘i, "naturalized and common along roadsides and in cultivated fields, 10-660 m" (Wagner et al., 1999; p. 1554).

Propagation:  "Seeds are dispersed by wind.  Spread is also by vehicles and machinery, e.g. road graders." (Smith, 2002; p. 75).

Native range:  Tropical and southern Africa; cultivated and naturalized elsewhere (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Fiji Fiji Islands	Fiji Islands	introduced invasive	Smith, Albert C. (1979) (pp. 380-381) Not common. Vouchers cited: DA 3586, DA 3632, DA 7235, DA 8315.
Fiji Fiji Islands	Viti Levu Island		Bishop Museum (Honolulu) (1952) (voucher ID: BISH 31695) Taxon name on voucher: Hyparrhenia rufa (Nees) Stapf
French Polynesia Society Islands	Raiatea (Havai) Island	introduced invasive	Welsh, S. L. (1998) (p. 338) Vouchers cited: Florence 4620, BRY 25740, BRY 26371
French Polynesia Society Islands	Raiatea (Havai) Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Voucher cited: J. Florence 3388 (PAP) Adventice
French Polynesia Society Islands	Raiatea (Havai) Island		Bishop Museum (Honolulu) (1982) (voucher ID: BISH 492124) Taxon name on voucher: Hyparrhenia rufa (Nees) Stapf
French Polynesia Society Islands	Raiatea (Havai) Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1981) (voucher ID: PTBG 38269) Taxon name on voucher: Hyparrhenia rufa
French Polynesia Society Islands	Tahiti Island	introduced invasive	Welsh, S. L. (1998) (p. 338) Voucher cited: Florence 3388
French Polynesia Society Islands	Tahiti Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Vouchers cited: J. Florence 4620 (PAP), W.A. Whistler & M. Guérin 23 (PAP) Adventice
French Polynesia Society Islands	Tahiti Island		Bishop Museum (Honolulu) (1983) (voucher ID: BISH 554433) Taxon name on voucher: Hyparrhenia rufa (Nees) Stapf
French Polynesia Society Islands	Tahiti Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1981) (voucher ID: PTBG 38310) Taxon name on voucher: Hyparrhenia rufa
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 44)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1554) Voucher cited: Judd s. n. (BISH)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1554)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1554)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1554)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1554)

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)	Northern Territory	introduced invasive	Smith, Nicholas M. (2002) (p. 75)
Australia Australia (continental)	Queensland	introduced invasive	Smith, Nicholas M. (2002) (p. 75)
Central America Central America (Pacific rim)	Costa Rica (Republic of)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (pp. 187-188)
Central America Central America (Pacific rim)	Honduras (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (pp. 187-188)
China China	China (People's Republic of)	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Colombia		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (pp. 187-188)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (pp. 187-188)
Thailand Thailand	Thailand (Kingdom of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (pp. 187-188)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island	uncertain if native	Lavergne, Christophe (2006) "Weed (indigène?)"
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island	introduced invasive cultivated	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
United States (continental except west coast) United States (other states)	USA (Florida)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Comments:  A serious weed in Colombia (Smith, 2002; p. 75). An aggressive weed in Costa Rica.

Control: 

Physical:  "Cutting before seeds ripen prevents seed dispersal"  (Weber, 2003; p. 207).