Hypericum perforatum L., Hypericaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results: 

Hawai‘i/Pacific:  High risk, score: 12 (Go to the risk assessment)
Risk assessment from the Government of Queensland, Australia (PDF format).

Common name(s): [more details]

Chinese: guan ye lian qiao

English: goatweed, Klamath weed, St. John's-wort

French: herbe à mille trous, millepertuis commun

Spanish: corazoncillo, hierba de San Juan

Habit:  herb

Description:  "Rhizomatous perennial herbs; stems 1 to several, erect, becoming somewhat woody toward base, 5-10 dm long, black-dotted.  Leaves linear to elliptic or oblanceolate, primary ones 10-30 mm long, 3-16 mm wide, usually black-dotted.  Flowers in paniculate cymes; sepals connate at base, the lobes lanceolate, 3-5 mm long, glandular punctate; petals obovate, 5-8 mm long, black-dotted along margins; stamens numerous, in 3 clusters; styles 3 (4).  Capsules ovoid, 7-8 mm long.  Seeds dark brown, cylindrical, ca. 1 mm long, the surface pitted"  (Wagner et al., 1999; p. 546).

Habitat/ecology:  "Grass- and woodland, riverbanks, disturbed areas.  This plant forms extensive and dense colonies where invasive, eliminating native vegetation.  Seedlings are sensitive to competition but established plants compete successfully with native forbs and grasses.  The weed cannot survive in densely shaded areas"  (Weber, 2003; p. 210).  "In Chile this species grows in the following environmental conditions:  Medium altitude up to the timber line; low altitude, interior valleys; coastal mountains, 500-2000 m; coastal areas, 0-500 m.  Somewhat dry areas where the drought may last 3-5 months, precipitations of 400-800 mm. are concentrated in winter.  Fully exposed to the sun, level areas or slopes facing north; some shadow, some protection against direct sunlight, some shadow from vegetation, filtering about 20-40% of light (Chileflora).

Propagation:  "Quick maturing, relatively long-lived, produces many long-lived seeds and a tough rhizome system. Seeds spread by wind (minor), and possibly livestock. Rhizomes spread by soil and water movement and greenwaste dumping. Sources of seed and rhizomes for new infestations include roadsides, pasture, wasteland, riverbeds and gardens. Increasingly cultivated as a medicinal herb"  (Weedbusters New Zealand).

Native range:  "Native to Eurasia, widely naturalized" (Wagner et al., 1999; p. 546).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 554)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 546) Voucher cited: Fosberg 42087 (BISH)

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)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Chile (continental) Chile	Chile (Republic of)	introduced invasive	Belov, Michail (2011)
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 183) var. perforatum and var. angustifolium DC.
New Zealand New Zealand	New Zealand (country)	introduced invasive	Owen, S. J. (1997)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 544) "A particularly troublesome weed in tussock grasslands, also very common in pastures, roadsides, riverbeds, waste places and in many modified open communities".

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mascarene Islands Mascarene Islands (Mauritius, La Reunion, Rodrigues)	Mascarene Islands	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Comments:  "A serious weed, and its potential for photosensitization poses a threat to livestock in many parts of the world" (Wagner et al., 1999; p. 546).

Control:  "Can resprout from rhizomes and seed bank reinfests bared sites  Can be left in regenerating bush and shrubland, as will disappear as light levels fall"  (Weedbusters New Zealand).

Physical:  "Seedlings and smaller plants can be hand pulled or dug out, crowns and rhizomes must be removed.  Repeated defoliation can reduce the plant's density".

Chemical:  "Effective herbicides are 2,4-D, glyphosate, or picloram.  Bare ground resulting from control measures is likely to be colonized by emerging seedlings"  (Weber, 2003; p. 210).

"1. Weed wipe (spring-summer only): glyphosate (333ml/L + penetrant) or metsulferon-methyl 600g/kg  (5g/L+ penetrant). 2. Spray (spring-summer only): glyphosate (10ml/L) or metsulferon-methyl 600g/kg (1g/10L).

Biological:  Chrysolina beetle"  (Weedbusters New Zealand).

Additional information:
Best Practice Management Guide produced by the CRC for Australian Weed Management (PDF format).
Information from the Global Invasive Species Database.
Species profile from the U.S. Department of Agriculture's National Invasive Species Information Center.
Information sheet from Weedbusters New Zealand.
Photos and other information from Chileflora.

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

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

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

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Belov, Michail. 2011. Chileflora (online resource).

Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido. 2006. Nouveau catalogue de la flore vaculaire de l'archipel Juan Fernández (Chile) [Nuevo catálogo de la flora vacular del Archipélago Juan Fernández (Chile)]. Acta Bot. Gallica 153(4):399-587.

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

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

Owen, S. J. 1997. Ecological weeds on conservation land in New Zealand: A database. Working draft. Wellington, New Zealand. Department of Conservation.

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

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

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.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.

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