Najas guadalupensis (Spreng.) Magnus, Hydrocharitaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Caulinia guadalupensis Spreng.

Common name(s): [more details]

English: Guadalupe waternymph, common waternymph, southern naiad, southern waternymph

French: naïade de la Guadeloupe

Habit:  aquatic herb

Description:  "Stems often profusely branched distally, 11-90 cm x 0.1-2 mm; internodes 0.1-9 cm, without prickles. Leaves spreading with age, 0.3-3.3 cm, lax in age; sheath 1-3.4 mm wide, apex rounded to truncate; blade 0.2--2.1 mm wide, margins minutely serrulate, teeth 18--100 per side, apex rounded to truncate, slightly auriculate, with 1-3 teeth, teeth unicellular; midvein without prickles abaxially. Flowers 1-3 per axil, staminate and pistillate on same plants. Staminate flowers in distal axils, 1.5-3 mm; involucral beaks 4-lobed, 0.2-1.3 mm; anther 1- or 4-loculed, 1-1.7 mm. Pistillate flowers in proximal axils, 1.5-4 mm; styles 0.3-1.5 mm; stigmas 4-lobed. Seeds not recurved, yellowish white with purple tinge, fusiform, 1.2-3.8 x 0.4-0.8 mm, apex with style situated at center; testa dull, 3 cell layers thick, pitted; aeroleareoles regularly arranged in 20-60 longitudinal rows, not ladderlike, 4-6-angled, longer than broad, end walls not raised"  (Flora of North America online).

"Plants monoecious with much-branched stems up to 6 dm long; leaves 1-2.5 cm long, 0.5-1 mm wide, generally evenly-spaced, flexible, the sheath rounded to obtuse at the junction with the blade, few-toothed, 1-celled, the apex with 1-4, short, 1-celled spines; staminate flowers 2-3 mm long, anthers 4-celled; pistillate flowers 2-3 mm long, stigmas 2-3; fruit surface dull, conspicuously reticulate, pitted"  (Herbst & Wagner, 1996; p. 11).

Habitat/ecology:  "Freshwater ponds, sluggish streams, and ditches"  (Herbst & Wagner, 1996; p. 11).

Propagation:  Seed and fragments. "The stems are brittle, and the plant is readily propagated by plant fragments"  (Imada, 2007; p. 37).

Native range:  "Native to North, Central and South America"  (Herbst & Wagner, 1996; p. 11).

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	introduced invasive	Herbst, Derral R./Wagner, Warren L. (1996) (p. 11) Vouchers cited: Stemmermann & Warshauer 7189 (BISH), Stemmermann & Luce 7178 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive cultivated	Imada, Clyde (2007) (p. 37) Vouchers cited: G. Staples 940 (BISH), C. Imada 2001-53 (BISH)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	El Salvador (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Chiapas, Yucatan
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (Oregon)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (Washington)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Canada Canada	Canada	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (continental except west coast) United States (other states)	United States (other states)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (continental except west coast) United States (other states)	USA (Florida)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Control:  If you know of control methods for Najas guadalupensis, please let us know.