Pacific Island Ecosystems at Risk (PIER)

  [   PIER species lists  ]   [   PIER home  ]

Myriophyllum spicatum
L., Haloragaceae
Click on an image for links to BIGGER PICTURES


Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 25 (Go to the risk assessment).

Common name(s): [more details]

Chinese: sui zhuang hu wei zao

English: Eurasian water-milfoil, Eurasian watermilfoil, spike watermilfoil

Japanese: hozakinofusamo, kingyomo

Habit:  aquatic herb

Description:  "A perennial or biennial, submersed, aquatic herb; stems flexible, sparsely or much branched, slender, becoming leafless toward base, 1 to 4 m length, with extreme of 12 m reported from western Himalayas in Asia; adventitious roots on lower side of stem when on or in mud with additional at the upper surface prior to fragmentation; leaves dimorphic, grayish-green, in whorls of 4 to 5, usually with 14 to 24 pairs of filiform obtuse segments, 6 to 12 mm in length, extending outward from axis to give feather-like appearance; bracts inconspicuous, shorter than stem internodes; inflorescence borne on terminal spike of main stem and branches, 5 to 20 cm long, usually plink, below the spike are 5 to 20 nodes with diameter twice that of remainder of stem, rigid, lying parallel to water surface, spike erect at anthesis, parallel to water surface at fruit set; flowers, staminate flowers on upper axils; pistillate flowers below, often with bisexual flowers in the transition zone, flowers verticillate in whorls of 4, 2-ranked, lower 2 to 4 whorls of floral bracts usually comb-like, often longer than flowers, upper bracts entire, broader than long and shorter than flowers; staminate flower sepals ovate to triangular, 0.5 by 0.3 mm, erect, petals wine red, auriculate, 2.5 mm long, falling at anthesis, stamens 8; pistillate flower sepals strongly reduced, semiorbicular, erect, 0.2 to 0.3 mm, petals spreading, 0.3 to 0.5 mm, falling soon after anthesis; bisexual flower sepals and petals as in pistillate flowers, petals reddish; fruit muricate (a rough surface with sharp projections), globoseovoid, about 2.5 mm long, 4-grooved with 2 somewhat wrinkled ridges adjacent to lines of dehiscence, separating into 4 nut-like fruits"  (Holm et al., 1997; p. 482).

"Perennial aquatic herb with submerged stems to 2 m long.  Leaves in whorls of four, sessile, feathery; 2-3.5 cm long.  Inflorescence an aerial, terminal spike 3-8 cm long with 4 flowers at each node.  Female flowers in lower whorls with petals to 1 mm long; male flowers in upper whorls, with 4 reddish petals to 2.5 mm long, and 8 stamens.  Fruit ovoid, to 2.5 mm long, with 4 dry, 1-seeded nutlets."  (Waterhouse & Mitchell, 1998; pp 45-46).

Habitat/ecology:  "Freshwater wetlands, lakes, coastal estuaries.  This aquatic is most common in waters of 1-3 m depth, but can invasde waters up to 10 m deep.  It forms dense stands that shade out other species and alter the temperature profile of the water body.  It flourishes in lakes with nutrient rich water, and the spread of the plant is promoted by eutrophication"  (Weber, 2003; p. 278).  "Lakes, canals and reservoirs. Tolerates a wide pH range and brackish water. Can survive stranding, and depths up to 17 m. It chokes lakes and water storages, affecting fish and shellfish production, recreation and boat traffic." (Waterhouse & Mitchell, 1998; pp 45-46).

Propagation:  "Vegetative fragments and seed spread by moving water and water birds" (Waterhouse & Mitchell, 1998; pp 45-46).

Native range:  Eurasia (Waterhouse & Mitchell, 1998; pp 45-46).

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
Maui Island introduced
Wester, Lyndon (1992) (p. 141)
Philippines
Philippine Islands
Philippine Islands   Waterhouse, B. M./Mitchell, A. A. (1998) (p. 46)
Philippines
Philippine Islands
Philippine Islands   Merrill, Elmer D. (1923) (p. 221)
In shallow water of Lake Lanao, altitude 670 m.
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. (2013)
Naturalized
Cambodia
Cambodia
Cambodia (Kingdom of)   Waterhouse, B. M./Mitchell, A. A. (1998) (p. 46)
Canada (British Colombia)
Province of British Columbia
Canada (British Columbia)   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 492)
China
China
China (People's Republic of) native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Stagnant waters, lakes, ditches, slow streams, springs; near sea level to 4200 m, rarely to 5200 m in springs in Xizang. Throughout China.
China
China
Hong Kong native
Wu, Te-lin (2001) (p. 158)
Indonesia
Indonesia
Indonesia (Republic of)   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 480)
Japan
Japan
Japan (country) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Hokkaido, Honshu, Kyushu, Shikoku
South Korea
South Korea
South Korea (Republic of)   Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 243)
Taiwan
Taiwan Island
Taiwan Island native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Thailand
Thailand
Thailand (Kingdom of)   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 480)
United States (west coast)
United States (west coast states)
USA (Oregon) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (west coast)
United States (west coast states)
USA (California) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (west coast)
United States (west coast states)
USA (Washington) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
Vietnam
Vietnam
Vietnam (Socialist Republic of)   Waterhouse, B. M./Mitchell, A. A. (1998) (p. 46)
Also reported from
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Canada (except British Colombia)
Canada
Canada (country) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (continental except west coast)
United States (other states)
United States (other states) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (continental except west coast)
United States (other states)
United States (other states) introduced
invasive
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Naturalized
United States (continental except west coast)
United States (other states)
USA (Florida) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)

Comments:  "A serious weed in South Africa and USA, and a principal weed in India" (Waterhouse & Mitchell, 1998; pp 45-46).

Control:  See "Biology and control of aquatic plants: A best management practices handbook" for control information (large file, PDF format).

Physical:  "Plants can be removed by mechanical harvesters, although this may enhance stem fragmentation".

Chemical: "The plant is highly susceptible to 2,4-D.  Regrowth is fast if plants are not killed, and repeated control is necessary"  (Weber, 2003; p. 278).


Need more info? Have questions? Comments? Information to contribute? Contact PIER! (pier@hear.org)

  [   PIER species lists  ]   [   PIER home  ]

This page was created on 14 MAR 2005 and was last updated on 19 JAN 2011.