Nasturtium microphyllum (Boenn.) Reichb., Brassicaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Rorippa microphylla (Boenn. ex Rchb.) Hyl. ex Á. Löve & D. Löve

Common name(s): [more details]

English: one-row watercress

Hawaiian: lēkō

Japanese: chisa, kawara-chisa

Mangarevan: maru

Habit:  herb

Description:  "Aquatic or semiaquatic, somewhat fleshy, glabrous perennial herbs; stems floating, prostrate, or ascending, rooting at the nodes, hollow, 1-6 dm long, usually 2-6 mm in diameter.  Leaves pinnately compound with (3-) 6-9 leaflets, these ovate to elliptic, 1.5-4 cm long, 0.5-2 cm wide, margins subentire to sinuate-dentate, the terminal one often larger than lateral ones.  Pedicels 11-20 mm long in fruit; petals white, ca. 4 mm long.  Siliques 1.6-2.5 cm long.  Seeds in 1 row per cell, with ca. 100 polygonal depressions on each face" (Wagner et al., 1999; p. 411).

Habitat/ecology:  In Hawai‘i, "naturalized in running water or seasonally wet areas" (Wagner et al., 1999; p. 411).

Propagation:  Seed, vegetatively

Native range:  "Native to western Europe, widely cultivated as a food plant and widely naturalized in many areas" (Wagner et al., 1999; p. 411).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
French Polynesia Gambier Islands	Mangareva (Gambier) Island	introduced cultivated	St. John, Harold (1988) (p. 14) Voucher cited: St. John 14862 (BISH) Persisting from cultivation.
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 411)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 411)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 411)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive cultivated	Wysong, Michael/Hughes, Guy/Wood, K. R. (2007) (p. 3) Voucher cited: Wysong 557 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 411)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 183)

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

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

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

References:

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.

St. John, Harold. 1988. Census of the Flora of the Gambier Islands, Polynesia. Pacific Plant Studies 43. Honolulu, Hawaii. 34 pp. [Privately published].

Staples, George W./Herbst, Derral R. 2005. A tropical garden flora: plants cultivated in the Hawaiian Islands and other tropical places. Bishop Museum Press, Honolulu. 908 pp.

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).

Wysong, Michael/Hughes, Guy/Wood, K. R. 2007. New Hawaiian plant records for the island of Moloka‘i. In: Evenhuis, Neal L. and Eldredge, Lucias G., eds. Records of the Hawaii Biological Survey for 2006. Part 2: Notes. Bishop Museum Occasional Papers 96:1-8.