Hydrolea zeylanica (L.) Vahl, Hydroleaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Other Latin names:  Nama zeylanica L.

Common name(s): [more details]

Chinese: tian ji ma

Habit:  aquatic herb

Description:  "Soft, unarmed, herbaceous perennial, but flowering the first year from seed, therefore seemingly annual, 7-100 cm tall or more, often repent and repeatedly branched, rooting from the lower nodes.   Stems glabrous below the flowering branches.  Leaves glabrous or very thinly puberulent on the petiole, veiny below, lanceolate to elliptic, 2-12 cm long, 6-12 mm wide, on winged petioles up to 5 mm long.  Flowers in irregularly bracted racemes or panicles, the inflorescence branches, pedicels, and calyces stipitate glandular (or merely puberulent, or even entirely glabrous, this eglandular phase apparently rare in Ceylon).  Calyx 5-6.5 mm long, divided nearly to base; corolla blue, glabrous, 5 mm long, lobes spreading.  Stamens not or barely esxert, filaments glabrous, anthers deeply sagitate at base.  Ovary ellipsoid, hairy above, 2.5 mm high in flower.  Styles separate to base, stimas capitate.  Fruit capsular, 4-4.5 mm high, septicidally dehiscent, seated in the persistent calyx; seeds numerous, less than 0.5 mm long" (Dassanayake, 1991; pp. 385-386).

Habitat/ecology:  In China (native), "paddies, pond margins, streamsides, open forests, swampy or inundated soil; 0-1000 m"  (Flora of China online).  In Sri Lanka, "widespread in moist situations around ponds and tnaks, in irrigation ditches, and in wet depressions" (Dassanayake, 1991; pp. 385-386).

Propagation:  Seed, rooting at nodes (Dassanayake, 1991; pp. 385-386).

Native range:  India through southeast Asia, Malesia, China, Taiwan and northern Australia (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Philippines Philippine Islands	Philippine Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Philippines Philippine Islands	Philippine Islands		Merrill, Elmer D. (1923) (pp. 372-373) In open wet places, often a common rice-paddy weed.

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	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Australia Australia (continental)	Queensland	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
China China	China (People's Republic of)	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2011)
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Singapore Singapore	Singapore (Republic of)	uncertain if introduced invasive	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 49) Weed of uncertain origin
Taiwan Taiwan	Taiwan Island	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Thailand Thailand	Thailand (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Vietnam Vietnam	Vietnam (Socialist Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

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

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

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

References:

Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. 2009. A checklist of the total vascular plant flora of Singapore: native, naturalised and cultivated species. Raffles Museum of Biodiversity Research, National University of Singapore. 273 pp.

Dassanayake, M. D., gen. ed. 1991. A revised handbook to the flora of Ceylon. Vol VII. Amerind Pub. Co., New Delhi. 439 pp.

Merrill, Elmer D. 1923. An enumeration of Philippine flowering plants, vol. 3 [reprint]. Bureau of Printing, Manila. 628 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

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