Hypericum japonicum Thunb., Clusiaceae

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Present on Pacific Islands?  no

Threat only at high elevations?  no

Common name(s): [more details]

English: Japanese St. John's wort, matted St. John's-wort, swamp hypericum

Habit:  herb

Description:  "Prostrate to erect perennial herb, often forming mats and rooting at nodes, lacking black glands. Stems very slender, generally < 15 cm long, 4-angled, often brownish or reddish purple, ascending towards apex when flowering; internodes often short. Leaves sessile, (1)-3-7-(10) x (0.5)-1-3-(5) mm, usually ovate, oblong-ovate, elliptic, or obovate, occasionally linear, with pellucid glands; margin flat or undulate and crisped; base cuneate to rounded. Flowers terminal, solitary or few in cymes. Sepals 2-4 mm long, linear-oblong. Corolla (4)-5-8-(c. 10) mm in diameter., orange-yellow, = or a little > sepals. Stamens ± forming 3 bundles. Styles 3. Capsule 2-4.5 mm in diameter., broadly ellipsoid-ovoid to suborbicular, dry. Seeds 0.4-0.6 mm long, broad-cylindric to ellipsoid, reticulate" (Webb et al., 1988; p. 546).

Habitat/ecology:  In New Zealand, "lowland to montane open places, especially wet ground, sometimes in modified communities" (Webb et al., 1988; p. 546).

Propagation:  Seed

Native range:  Southern and eastern Asia, Australia, New Zealand (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)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Philippines Philippine Islands	Philippine Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)

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	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Australia Australia (continental)	Queensland	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Japan Japan	Japan (country)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
New Zealand New Zealand	New Zealand (country)	native	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 546)
Taiwan Taiwan	Taiwan Island	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Thailand Thailand	Thailand (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)
Vietnam Vietnam	Vietnam (Socialist Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2008)

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

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

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

References:

Hafliger, Toni J./Wolf, Matthias. 1988. Dicot weeds, vol. 1. CIBA-GEIGY Ltd., Basle, Switzerland. 335 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2008. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.