Pacific Island Ecosystems at Risk (PIER)

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Polygonum dichotomum
Blume, Polygonaceae
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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Chinese: er qi liao

Tahitian: pitorea

Habit:  herb

Description: 

Genus:  "Erect, sprawling, or scandent herbs or shrubs; leaves with an amplexicaul ocrea, this often with longitudinal nerves extending into bristles on its upper margin; inflorescences usually spicate, the spikes sometimes aggregated into compound inflorescences; flowers hermaphrodite or sometimes polygamous, usually cymose-fascicled in axils of bracts or sometimes in leaf axils; tepals 5, acyclic, sometimes colored, subequal after anthesis; stamens 4-9; ovary compressed and with 2 styles (in our species [Fiji]) or trigonous and with 3 styles, the stigmas capitate; fruit lenticular (in our species) or trigonous-subglobose"  (Smith, 1981; pp. 306-307).

Species:  "As seen in Fiji, Polygonum dichotomum is a perennial, sprawling herb, with branches ascending to 1.2 m when support is available...  Its leaf blades are ovate-lanceolate and up to 20 x 5 cm but often smaller, usually abruptly obtuse at base, and its tepals are white"  (Smith, 1981; pp. 306-307).

"A glabrous annual herb; stems 4-ridged, branched and retrosely prickly, prostrate and rooting at nodes in the lower part, ascending or erect in the upper part.  Leaves membranous, broadly lanceolate, 5-10 cm long, acute or obtuse at apex, deeply cordate or sagittate at base, glaucous, glabrous on both sides, the margins entire; petioles 7-20 mm long, often with recurved prickles; ochreae scarious, 15-20 mm long, obliquely cut, not ciliate.  Inflorescence leaf-opposite, mostly 1-2 times dichotomously branched; flowers in terminal dense short-spikes, the spike together with the glandular peduncle 2-2.5 cm long; perianth pinkish or reddish-purple, 2-3 mm long, 5-lobed, the lobes broadly elliptical.  Nuts orbicular, biconvex, striate, black, punctulate" (Li et al., 1976; pp. 236, 270).

Description from Flora of China online.

Habitat/ecology:  In Fiji, "occurring from near sea level to an elevation of 825 m in swampy areas, on the shores and in the shallow water of lakes and ponds, and in moist areas in the forest-grassland transition" (Smith, 1981; pp. 306-307).  In Taiwan, "usually along irrigation ditches or in swampy places at lower altitudes throughout the island" (Li et al., 1976; pp. 236, 270).

Propagation:  Seed

Native range:  "Indigenous in India, China, and Formosa and into Malesia and Queensland.  It is probable that the species occurs east of Malesia only as an adventive, perhaps inadvertently carried by aboriginal voyagers" (Smith, 1981; pp. 306-307).

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
Taveuni Island introduced
invasive
abo. intro.
Smith, Albert C. (1981) (pp. 306-307)
Vouchers cited: DA 12401, DA 14366, Seemann 370 (K)
Fiji
Fiji Islands
Viti Levu Island introduced
invasive
abo. intro.
Smith, Albert C. (1981) (pp. 306-307)
Vouchers cited: Smith 5390, Vaughan 3335, DA 1501, DA 894, DA 2726
French Polynesia
Society Islands
Raiatea (Havai) Island introduced
invasive
Welsh, S. L. (1998) (p. 222)
Vouchers cited: Moore 770, BRY 26367
French Polynesia
Society Islands
Tahiti Island introduced
invasive
Welsh, S. L. (1998) (p. 222)
Vouchers cited: Parks & Setchell 128, Grant 4501
Tonga
Tonga Islands
Tonga Islands   Swarbrick, John T. (1997) (p. 95)
Wallis and Futuna
Wallis and Futuna (Horne) Islands
Wallis and Futuna Islands   Swarbrick, John T. (1997) (p. 95)
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) native
Smith, Albert C. (1981) (pp. 306-307)
Australia
Australia (continental)
Queensland native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
China
China
China (People's Republic of) native
Smith, Albert C. (1981) (pp. 306-307)
China
China
China (People's Republic of) native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
"Ditches, marshy areas; 100-1000 m".
China
China
Hong Kong native
Wu, Te-lin (2001) (pp. 82-83)
In wet places in valleys.
Indonesia
Indonesia
Indonesia (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Japan
Ryukyu Islands
Ryukyu Islands native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Malaysia
Malaysia
Malaysia (country of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Taiwan
Taiwan Island
Taiwan Island native
Smith, Albert C. (1981) (pp. 306-307)
Thailand
Thailand
Thailand (Kingdom of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Vietnam
Vietnam
Vietnam (Socialist Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)


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This page was created on 19 AUG 2002 and was last updated on 15 MAR 2012.