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. (2013)
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. (2013)
Australia Australia (continental)	Queensland	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
China China	China (People's Republic of)	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Paddies, pond margins, streamsides, open forests, swampy or inundated soil; 0-1000 m. Fujian, Guangdong, Guangxi, Hainan, S Yunnan
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
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 Island	Taiwan Island	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Paddies, pond margins, streamsides, open forests, swampy or inundated soil; 0-1000 m.
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)

Control:  If you know of control methods for Hydrolea zeylanica, please let us know.