Pacific Island Ecosystems at Risk (PIER)

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Hymenachne amplexicaulis
(Rudge) Nees, Poaceae
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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Risk assessment results:  Australia:  Reject, score: 21 (Go to the risk assessment)
Risk assessment from the Government of Queensland, Australia (PDF format)

Common name(s): [more details]

Chinese: mo fu cao

English: hymenachne, olive hymenachne, trompetilla, West Indian marsh grass

Spanish: camalote

Habit:  grass

Description:  "Habit: Perennial. Culms decumbent; robust; 200-350 cm long; spongy; rooting from lower nodes. Culm-internodes solid. Culm-nodes glabrous. Leaf-sheaths glabrous on surface; outer margin glabrous, or hairy. Ligule an eciliate membrane; 1-2.5 mm long. Leaf-blade base amplexicaul. Leaf-blades lanceolate; 15-33 cm long; 12-28 mm wide. Leaf-blade surface glabrous. Leaf-blade margins scabrous; tuberculate-ciliate; hairy at base. Leaf-blade apex acuminate. Inflorescence: Inflorescence a panicle. Panicle spiciform; linear; 10-40 cm long; 1-2 cm wide. Spikelets solitary. Fertile spikelets pedicelled. Pedicels oblong. Fertile spikelets: Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets lanceolate; dorsally compressed; acuminate; 3.5-5.5 mm long; falling entire. Glumes: Glumes dissimilar; shorter than spikelet; thinner than fertile lemma. Lower glume ovate; 1-1.7 mm long; 0.3 times length of spikelet; hyaline; without keels; 3 -veined. Lower glume apex cuspidate. Upper glume lanceolate; 2.8-3.9 mm long; 0.7-0.8 times length of spikelet; membranous; without keels; 5 -veined. Upper glume apex caudate; awned; 1-awned. Upper glume awn 0.5 mm long. Florets: Basal sterile florets barren; without significant palea. Lemma of lower sterile floret similar to upper glume; lanceolate; 3.6-4.6 mm long; 1 times length of spikelet; membranous; 5 -veined; caudate. Fertile lemma lanceolate; 2.5-3.5 mm long; cartilaginous; pallid; without keel; 3-veined. Lemma margins involute. Lemma apex acuminate. Palea separating from lemma above; involute; 1 times length of lemma; cartilaginous; 2-veined; without keels. Palea apex acuminate. Flower: Anthers 3; 1.1-1.2 mm long. Fruit: Caryopsis ellipsoid" (GrassBase).

Habitat/ecology:  "Swampy situations such as riverbanks and seasonally flooded areas in water up to 2 m deep.  It has the ability to smother native vegetation and form dense and extensive monospecific stands." (Smith, 2002; p. 74). Grows in water up to 2 m deep in periodically inundated wetlands. It does not grow in permanent water and requires alternating periods of flooding and dryness to establish and survive (Csurhes and Edwards, 1998; pp. 168-169).  "As a semi-aquatic grass, hymenachne thrives best on clay soils that are inundated during the wet season rains but dry out to some extent in the dry season. The subsoil must remain moist during the dry season, as hymenachne can only withstand short periods of drought. Consequently, it is found mainly in low-lying areas along the edges of permanent water. Hymenachne can withstand prolonged (40 weeks) flooding by growing above floodwaters. Because it grows so rapidly, it flourishes in wetlands that receive sediment and nutrient-rich water, and it may be a good indicator of such pollution. However, it does not tolerate brackish water and does not grow well in shaded areas"  (Australian Weed Management Guide).

Propagation:  Seed, dispersed by floodwater or in contaminated stock feed. Pieces of plants can also be carried to new locations by flood water. Promoted as a pasture grass. (Csurhes & Edwards, 1998; pp. 168-169).

Native range:  Mexico, Caribbean Islands, Central and South America; 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
Papua New Guinea
Papua New Guinea (eastern New Guinea Island)
Papua New Guinea (eastern New Guinea Island)   Henty, E. E. (1969) (p. 109)
Widely spread, in shallow water at the margins of swamps and slow rivers, at low altitudes.
Philippines
Philippine Islands
Philippine Islands introduced
invasive
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Naturalized
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)
New South Wales introduced
invasive
National Herbarium of New South Wales (2013)
A local cultivar (cv. 'Olive') has become naturalised and posing a threat to natural wetlands in the tropics and warm temperate areas.
Australia
Australia (continental)
Northern Territory introduced
cultivated
Csurhes, S./Edwards, R. (1998) (pp. 168-169)
Australia
Australia (continental)
Northern Territory introduced
invasive
cultivated
Smith, Nicholas M. (2002) (p. 74)
Spreading throughout the Adelaid and Mary River flood plains.
Australia
Australia (continental)
Queensland introduced
invasive
cultivated
Csurhes, S./Edwards, R. (1998) (pp. 168-169)
China
China
China (People's Republic of)   Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Streams in shallow water, ricefields; below 1000 m. Hainan, Yunnan.
Colombia
Colombia
Colombia (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Costa Rica
Costa Rica
Costa Rica (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Ecuador (Mainland)
Ecuador
Ecuador (Republic of) (continental) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
El Salvador
El Salvador
El Salvador (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Guatemala
Guatemala
Guatemala (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Honduras
Honduras
Honduras (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Indonesia
Indonesia
Indonesia (Republic of)   Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 187)
Malaysia
Malaysia
Malaysia (country of) introduced
invasive
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Naturalized
Mexico
Mexico
Mexico (United Mexican States) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Nicaragua
Nicaragua
Nicaragua (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Panama
Panama
Panama (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Perú
Perú
Perú (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Singapore
Singapore
Singapore (Republic of) native
Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 50)
Common
Taiwan
Taiwan Island
Taiwan Island   Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Streams in shallow water, ricefields; below 1000 m.
Thailand
Thailand
Thailand (Kingdom of) introduced
invasive
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Naturalized
Vietnam
Vietnam
Vietnam (Socialist Republic of) 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
United States (continental except west coast)
United States (other states)
USA (Florida) introduced
invasive
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Naturalized

Comments:  A "weed of national significance" in Australia. Has invaded tropical wetlands in Queensland.

Planting of this species is prohibited in Miami-Dade County, Florida (U.S.) (Miami-Dade County Dept. of Planning and Zoning, 2010).

Control:  "Established plants are difficult to control.  Scattered plants may be removed manually, all stolons and roots must be removed to prevent regrowth.  Larger patches can be treated with herbicides approved for use in aquatic environments"  (Weber, 2003; p. 206).


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This page was created on 1 JAN 1999 and was last updated on 8 MAY 2017.