Justicia procumbens Linnaeus, Acanthaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: waterwillow

Habit:  herb

Description:  "Decumbent perennial herb up to 40 cm in height.  Stems pubescent, rooting at the lower nodes.  Leaves opposite, simple, elliptic to ovate, 1-4 x 0.6-1.5 cm, acute at the apex and base, surfaces glabrous to sparsely pubescent; margins ciliate; petiole 1-4 mm long.  Inflorescence of 1-3 dense, ovoid to cylindrical, axillary or terminal racemes 0.6-6 cm long.  Calyx 3-6 mm long, deeply divided into 5 linear lobes with hairy margins. subsessile, subtended by two bracts similar to the calyx lobes.  Corolla bilabiate, 4-7 mm long, shallowly divided into 2 lobes on the small upper lip and 3 on the lower, larger, suborbicular lip, lavender with white markings.  Stamens 2, epipetalous, included.  Ovary superior, 2-celled.  Fruit an ovoid capsule 4-5 mm long, splitting and spreading open by 2 valves, 4-seeded"  (Whistler, 1995; p. 19).

Habitat/ecology:  "Common in disturbed places"  (Whistler, 1995; p. 19).

Propagation:  Seed

Native range:  Tropical America (Whistler, 1995; p. 19).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
American Samoa Tutuila Islands	Tutuila Island		Whistler, W. A. (1988) (p. 5) Voucher cited: McKee 2950
Philippines Philippine Islands	Philippine Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)
Samoa Western Samoa Islands	Savai‘i Island		Whistler, W. A. (1988) (p. 5) Voucher cited: Whistler 1235
Samoa Western Samoa Islands	Upolu Island		Whistler, W. A. (1988) (p. 5) Voucher cited: Parham 9011
Samoa Western Samoa Islands	Upolu Island	introduced invasive	Space, James C./Flynn, Tim (2002) (p. Field notes.)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)
Indonesia Indonesia	Indonesia (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 202)
Japan Japan	Japan (country)	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)
Japan Ryukyu Islands	Ryukyu Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)
Taiwan Taiwan	Taiwan Island	native	U.S. Dept. Agr., Agr. Res. Serv. (2009)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Maldives Maldive Islands	Malè Atoll		Fosberg, F. R. (1957) (p. 34)

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

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

Taxonomic information about Justicia procumbens may be available from the Germplasm Resources Information Network (GRIN).

References:

Fosberg, F. R. 1957. The Maldive Islands, Indian Ocean. Atoll Research Bulletin No. 58. Pacific Science Board, National Academy of Sciences, Washington. 37 pp.

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.

Space, James C./Flynn, Tim. 2002. Report to the Government of Samoa on invasive plant species of environmental concern. USDA Forest Service, Honolulu. 83 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2009. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Whistler, W. A. 1988. Checklist of the weed flora of western Polynesia. Technical Paper No. 194, South Pacific Commission, Noumea, New Caledonia. 69 pp.

Whistler, W. A. 1995. Wayside Plants of the Islands. Isle Botanica, Honolulu. 202 pp.