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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.




Myriophyllum heterophyllum
Myriophyllum heterophyllum
(variable-leaf watermilfoil)
Plants
Native Transplant
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Myriophyllum heterophyllum Michx.

Common name: variable-leaf watermilfoil

Synonyms and Other Names: None

Taxonomy: available through www.itis.govITIS logo

Identification: A perennial herbaceous submersed aquatic plant that produces a short, emergent floral spike above the waterline.  Submersed leaves (2-4.5 cm long) are pinnately divided into 4-10 leaflet pairs, giving them a feather-like appearance and are arranged in whorls of 4-6 around a stout stem (3 mm in diameter).  

Native Range: Native to United States, but historically known only in the Southeast and Midwest.  
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Alaska
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Hawaii
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Puerto Rico &
Virgin Islands
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Guam Saipan
Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Myriophyllum heterophyllum are found here.

StateYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Alabama201420142Lower Tallapoosa; Middle Chattahoochee-Walter F
Connecticut193220139Farmington; Housatonic; Lower Connecticut; Pawcatuck-Wood; Quinebaug; Quinnipiac; Saugatuck; Shetucket; Thames
Maine196820176Dead; Lower Androscoggin; Lower Kennebec; Piscataqua-Salmon Falls; Presumpscot; Saco
Massachusetts1940201612Blackstone; Cape Cod; Charles; Chicopee; Concord; Housatonic; Merrimack River; Miller; Narragansett; Nashua; Quinebaug; Westfield
New Hampshire1970201610Black-Ottauquechee; Contoocook; Merrimack River; Middle Connecticut; Miller; Nashua; Pemigewasset; Piscataqua-Salmon Falls; Saco; Winnipesaukee River
New York1953201520Ausable River; Black; Chenango; Hackensack-Passaic; Hudson-Wappinger; Irondequoit-Ninemile; Lake Champlain; Lake Ontario; Lower Hudson; Mohawk; Northern Long Island; Oneida; Oswegatchie; Raquette; Sacandaga; Salmon-Sandy; Saranac River; Seneca; Southern Long Island; Upper Hudson
Oregon200020172Pacific Northwest Region; Siltcoos
Rhode Island197320152Blackstone; Pawcatuck-Wood
Vermont200820092Lake Champlain; Waits
Washington200620072Nisqually; Puget Sound

Table last updated 11/30/2018

† Populations may not be currently present.


Means of Introduction: Released aquarium or pond plants. Secondary spread possible through hitchhiking on boats/trailers or waterfowl.

Remarks: Molecular data supports the fact that some aggressively growing populations of variable-leaf milfoil are actually hybrids between M. heterophyllum and the native M. pinnatum; these hybrids, found in Connecticut, propagate primarily vegetatively (Moody & Les 2002).  Populations sampled from 25 lakes in New Hampshire, however, suggest that the pure M. heterophyllum is also capable of forming aggressively-spreading, monotypic stands (Thum & Lennon 2006).

References: (click for full references)

Crow, G. E. and C. B. Hellquist.  2000. Aquatic and wetland plants of Northeastern North America.  Volume 1. The University of Wisconsin Press, Madison, Wisconsin.

Les, D.H. and L.J. Mehrhoff. 1999. Introduction of nonindigenous aquatic vascular plants in sourhtern New England: a historical perspective. Biological Invasions. 1(2/3). pp. 281-300.

Moody, M.L. and D.H. Les. 2002.  Evidence of hybridity in invasive watermilfoil (Myriophyllum) populations.  Proceedings of the National Academy of Science 99(23): 14867–14871.

Thum, R.A. and J.T. Lennon. 2006. Is Hybridization Responsible for Invasive Growth of Non-indigenous Water-milfoils?  Biological Invasions 8(5): 1061-1066. 

Author: Howard, V.

Revision Date: 10/31/2008

Citation Information:
Howard, V., 2019, Myriophyllum heterophyllum Michx.: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=236, Revision Date: 10/31/2008, Access Date: 6/24/2019

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

Disclaimer:

The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2019]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/24/2019].

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