Mentha pulegium L., Lamiaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: European pennyroyal, pennyroyal, peppermint

French: menthe pouliot, pouliot

Spanish: poleo

Habit:  herb

Description:  "Aromatic, tomentose perennial herbs; stems procumbent to ascending, 1-4 dm long.  Leaves narrowly ovate to narrowly elliptic, 8-30 mm long, 0.4-12 mm wide, pubescent at least on lower surface, margins subentire or with up to 6 teeth on each side, base attenuate, sessile or subsessile.  Flowers in well-spaced verticillasters in the leaf axils; calyx (2-) 2.5-3 mm long, the teeth ciliate, lower ones subulate, upper ones slightly shorter and wider; corolla lilac, (4-) 4.5-6 mm long; stamens exserted beyond to included in corolla tube.  Nutlets pale brown, ca. 0.7-0.8 mm long"  (Wagner et al., 1999; p. 807).

Habitat/ecology:  "Grassland, riparian habitats, freshwater wetlands, alluvial plains.  A highly variable species with regard to growth habit and leaf shape.  Several varieties have been described in the native range where it hybridizes with several congeners.  The plant forms dense stands that crowd out native vegetation and reduce species richness.  Damaged plants easily resprout"  (Weber, 2003; p. 266).

In Hawai‘i, "cultivated and escaping from gardens, usually in damp areas"  (Wagner et al., 1999; p. 807).

Propagation:  Seed.  "It is a prolific seed producer, and seeds are dispersed by water and animals.  Seedlings can emerge and establish under water, enabling the plant to invade flooded areas.  It accumulates a soil seed bank"  (Weber, 2003; p. 266).

Native range:  "Native to Europe, widely naturalized" (Wagner et al., 1999; p. 807).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island		Bishop Museum (U.S.A. Hawaii. Honolulu.) (1948) (voucher ID: BISH 53279) Taxon name on voucher: Mentha pulegium L.
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 807) Voucher cited: Forbes 2633.M (BISH) Cultivated and escaping from gardens.
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced cultivated	MacKee, H. S. (1994) (p. 69) Voucher cited: MacKee 34795

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 invasive	U.S. Dept. Agr., Agr. Res. Serv. (2009)
New Zealand New Zealand	New Zealand (country)	introduced invasive cultivated	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 780) "Common to abundant in wet pastures, by rivers and lakesides, also in drier places, including bare lava and backs of sandy beaches".

Control: 

Physical:  "Single plants and small patches are hand pulled or dug out.  Roots and stolons must be removed to prevent regrowth.  Follow-up programs are necessary to treat regrowth and seedlings".

Chemical:  "Seedlings can be controlled with 2,4-D, established plants with glyphosate, metsulfuron-methyl, or triclopyr plus picloram"  (Weber, 2003; p. 266).

Additional information:
Information from the University of California

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

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

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

References:

Bishop Museum (U.S.A. Hawaii. Honolulu.). 1948. Voucher specimen #BISH53279(Greenwell, A.B.H. 19240).

MacKee, H. S. 1994. Catalogue des plantes introduites et cultivées en Nouvelle-Calédonie. Muséum National d'Histoire Naturelle, Paris, 164 p.

U. S. Government. 2009. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2009. 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.