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)
Native Transplant

Copyright Info
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.  

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.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CT193220219Farmington River; Housatonic; Outlet Connecticut River; Pawcatuck River; Quinebaug River; Quinnipiac; Saugatuck; Shetucket River; Thames
ME196820176Dead River; Lower Androscoggin River; Lower Kennebec River; Piscataqua-Salmon Falls; Presumpscot; Saco River
MA1940201712Blackstone River; Cape Cod; Charles; Chicopee River; Concord River; Housatonic; Merrimack River; Millers River; Narragansett; Nashua River; Quinebaug River; Westfield River
NH1965202010Ashuelot River-Connecticut River; Black River-Connecticut River; Contoocook River; Merrimack River; Millers River; Nashua River; Pemigewasset River; Piscataqua-Salmon Falls; Saco River; Winnipesaukee River
NJ201020101Middle Delaware-Musconetcong
NY1953201519Ausable River; Black; Chenango; Hackensack-Passaic; Hudson-Wappinger; Irondequoit-Ninemile; Lake Champlain; Lake Ontario; Lower Hudson; Mohawk; Northern Long Island; Oneida; Oswegatchie; Raquette; Salmon-Sandy; Saranac River; Seneca; Southern Long Island; Upper Hudson
OR200020172Pacific Northwest Region; Siltcoos
PA201020213Lackawaxen; Lehigh; Middle Delaware-Mongaup-Brodhead
RI197320152Blackstone River; Pawcatuck River
TX1917202414Austin-Travis Lakes; Buchanan-Lyndon B. Johnson Lakes; Buffalo-San Jacinto; Elm-Sycamore; Lampasas; Lower Colorado-Cummins; Lower Devils; Nueces Headwaters; San Gabriel; San Marcos; South Llano; Upper Frio; Upper Guadalupe; Upper West Fork Trinity
VT200820092Ammonoosuc River-Connecticut River; Lake Champlain
WA200620183Lake Washington; Nisqually; Puget Sound

Table last updated 4/22/2024

† 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: 9/28/2023

Citation Information:
Howard, V., 2024, 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: 9/28/2023, Access Date: 4/22/2024

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.


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. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [4/22/2024].

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