Environmental Review Toolkit
Water, Wetlands, and Wildlife

Volume 15, No. 1 2008

Greener Roadsides

Greener Roadsides archive

Image examples of the top invasive plants as described in the text. Losestrife, Alligator Weed, Arundo donax, Eurasian milfoil, Curly pondweed, H20 hyacinth, H20 lettuce, Hydrilla, Phragmites, Salvina.

arundo donax

Eurasian milfoil



H20 lettuce

hy drilla

left: H20 hyacinth, right: curly pondweed

Editor's Note

Shown are ten of the top invasive plants threatening our waters. Some of these waters exist within highway corridors as retention ponds, canals, culverts, mitigation streams, bogs and marshes, and/or runoff ditches. Corridor waters can connect, or be adjacent to, rivers and lakes where water sports, fishing, and hunting are enjoyed in each state. Aquatic weeds and other invaders are threatening active and passive uses of waters across the country. They wreak economic and environmental damage we cannot afford.

Control of "aquatic weeds" became eligible for Federal-Aid funding upon the passage of SAFETEA-LU, Section 6006. Guidance explaining this section was published on May 16, 2006. It explained terrestrial weed control and vegetation establishment funding provisions, but little about aquatic weeds. We already knew about the spread of riparian weeds like tamarisk, Russian olive, melaleuca and phragmites. Yet we found ourselves behind the curve in knowledge and best practices related to aquatics in general.

This issue provides a primer on aquatic weeds. Some of these species, like purple loosestrife, have been around for hundreds of years and have spread in the past few decades. Others, like giant salvinia, reached our shores only a decade ago. Salvinia is considered one of the world's worst weeds. Mats of this weed have grown to be more than 2 feet thick. Salvinia over-winters in the southern tier of states and is likely to continue to adapt to our changing climate. We all need to get ahead of the curve on aquatic weeds. It is the intention of this issue to help you get started!

Aquatic weed law is where this problem gets murky. Although we have had noxious weed law in the United States for more than two centuries, it has been applied only to plants that harm agriculture, human health, and the environment. Not until recent history has weed law included aquatic plants. Currently, states are adding them to noxious weed law or are creating new invasive species laws. As such laws emerge, other invasive aquatic plants will likely be added. Depending on your region of work, plants like water chestnut, Brazilian elodea, flowering rush, reed canarygrass, or saltwater cordgrass will be listed. We will need to pay attention. State aquatic weed laws or invasive weed laws typically apply to the "public waters of the State" or aquatic environments where "floating, emersed, submersed, ditchbank and wetland species" can establish.

Aquatic Weeds, A Primer

Bonnie L. Harper-Lore and Mark W. Skinner

What Are Aquatic Weeds?

During the 1970s and 1980s most land managers used terms like exotic, alien, non-native, or pest plant to describe invasive species. Enter the exotic, alien, non-native pest, the zebra mussel! In the 1990s, Congress added terms like aquatic nuisance species and non-indigenous species. These acts reflected a new understanding of pests that includes invasive species that are environmental and economic threats beyond traditional agriculture and terrestrial natural areas concerns.

State laws followed. Previously, state-listed aquatic weeds were mostly plants that offended our human aesthetic needs. Duckweed, a native plant that floats atop ponds and lakes, is a good example. Waterfowl prefer it but, in their snapshot view of a waterway, lakefront owners and boaters see it as weedy. Now, impacts to recreational and commercial uses as well as the natural environment and human health are reflected in aquatic weed law. Laws vary but legal definitions generally describe aquatic weeds as non-native plants (algae, floating, submerged, emergent, lake and river edge) that impact economic and environmental values. State laws apply to either: 1) "public waters of the State;" or 2) an aquatic environment where "floating, immersed, submersed, ditchbank and wetland species" can establish.

The contemporary view is that aquatic weeds are plants that invade our waters to cause economic and ecological harm. They are listed in state aquatic, noxious, and invasive plant laws.

Why a Transportation Interest?

In 2005, President Bush enacted the "Safe, Accountable, Flexible, Efficient, Transportation Equity Act: A Legacy for Users" (SAFETEA-LU) which includes Section 6006, "Control of Noxious Weeds and Aquatic Noxious Weeds and Establishment of Native Species." The law addresses funding eligibility for weed control and the establishment of vegetation, preferably native plants.

Guidance on aquatic weeds is pending. Aquatic weeds exist on some highway rights-of-way: ditches, holding ponds, mitigation banks, rivers, lakes, and wetlands. They are the responsibility of state departments of transportation as directed in each state weed law. Construction and maintenance practices both should reduce the spread of aquatic weeds as they do with terrestrial weeds. The eligibility established in SAFETEA-LU Section 6006 for use of Federal-Aid funds for control of noxious weeds and establishment of native plants also applies to aquatic weeds.

How Do Federal Aquatic Weed Laws Apply?

The passage of two Federal laws has greatly influenced subsequent state aquatic weed laws. These Federal Acts apply to exotic, alien, non-native animal and plant species.

  1. The 1990 Nonindigenous Aquatic Nuisance Prevention and Control Act (NANPCA) focused on prevention, detection, and monitoring of zebra mussel and other aquatic nuisance species that are economic threats. The Aquatic Nuisance Species (ANS) Task Force is an intergovernmental organization dedicated to implementing NANPCA. The Task Force coordinates governmental efforts with the private sector and other interests to prevent and control ANS.
    1. What are ANS? ANS are nonindigenous species (NIS) that threaten the diversity or abundance of native species or the ecological stability of infested waters, or affect commercial, agricultural, aquacultural, or recreational activities dependent on such waters. ANS include NIS that occur in inland, estuarine and marine waters and that currently, or potentially, threaten ecological processes and natural resources.
    2. The Task Force: The U.S. Fish and Wildlife Service (FWS) and the U.S. Coast Guard are primary sponsors of a national call to action and public awareness campaign called Protect Your Waters. Their Stop Aquatic Hitchhikers campaign defines aquatic hitchhikers as non-native, harmful aquatic plants, animals, or microscopic organisms that can readily be transported to other waters via popular recreational activities. The terms aquatic nuisance species, aquatic invasive species, and non-native, harmful aquatic species are used interchangeably throughout the campaign to describe aquatic hitchhikers. All regional panels use this campaign. http://www.protectyourwaters.net/aboutus.php
    3. Four Regional Panels exist under guidance of the Task Force:
  2. The 1996 National Invasive Species Act (NISA) broadened the scope to all waters of the United States and included invasive species that cause economic and ecological degradation or pose public health risks. This legislation included exotics like mitten crab, brown mussel, ruffe, Eurasian watermilfoil, and hydrilla. NISA also:
    • Reauthorized the Great Lakes Ballast Program and required ecological surveys.
    • Expanded a ballast water program to the Department of Defense, other national waters, demonstration of technologies and practices by Interior and Commerce.
    • Expanded the ANS Task Force with representatives from the Chesapeake Bay and San Francisco Bay-Delta Estuary Programs.
    • Encouraged and funded regional panels for 6 years.
    • Provided some $30M over 5 years for state, interstate, and tribal invasive species management plans, an Aquatic Nuisance Species Program, and Environmental Protection Agency (EPA) research grants.

    What are NIS? NIS are any species or other viable biological material that enters an ecosystem beyond its historic range, including any such organism transferred from one country into another. NIS include both exotics and transplants from other parts of the country. Synonyms for NIS include: introduced, foreign, exotic, alien, non-native, immigrant, and transplants.

State Aquatic Weed Laws:

Alabama, Arkansas, California, Delaware, Florida, Georgia, Hawaii, Louisiana, Maine, Massachusetts, Montana, New Hampshire, North Carolina, Oklahoma, South Carolina, Virginia, Vermont, Washington, West Virginia, and Wisconsin all have some type of aquatic weed law. Purple loosestrife is found on both traditional (terrestrial) and aquatic weed lists, which makes sense since it is found in wetlands and uplands. This is likely to happen in the future with other invasive plants that have broad soil and moisture tolerance or can evolve this tolerance.

State Invasive Plant Laws:

This brings us to another level of state regulation. An invasive plant law listing aquatic plants now exists in Maine. Invasive plant laws authorize departments of natural resources or environmental quality/protection to act because these invasives are harmful to natural areas. It might be easier to maintain one state noxious weed list that includes both terrestrial and aquatic plants, and includes invasives of each category. However, until state departments of agriculture and natural resources can agree on shared authority, this is unlikely to happen.

Aquatic Weed Control, A Historical Account


The River and Harbor Act began control of aquatic plants in navigable waterways by the Army Corps of Engineers (COE). Mechanical controls used at this time.


Wisconsin used sodium arsenite to treat lakes. Replaced in the 1940s by selective, biodegradable, chemicals.


The Bureau of Reclamation (BR) used mostly mechanical means to control weed-free irrigation systems, canals, and drains.


Until then, the FWS relied on water level manipulation with increased waterfowl habitat as their objective. By 1945, all three agencies (COE, BR, and FWS) recognized the limitations of mechanical controls (water fluctuation, burns, mowing and harvesting).


The USDA assumed role of lead agency in aquatic weed research. New herbicides became a cheaper alternative to mechanical controls. Use of 2-4D common.


An alligator-weed flea beetle (Agasicles hygrophyila) succeeded in Southeast.


Grass carp introduced as biocontrol to aquaculture in Alabama. Escaped in the 1970s.


The EPA entered the scene focusing on a cause of weed spread, eutrophication of waters. Attitude shift from weed target to consideration of total environment.


The EPA allowed few aquatic herbicides through their screening. Thus biocontrols like grass carp and insects were released to control aquatic plants.


States continue to debate how much and how to control aquatic weeds. States began to take policy action against advances of exotic or non-native plant species.


The FWS provided a "Purple Loosestrife Alert."


The NANPCA called for four regional panels.


The Great Lakes panel on Aquatic Nuisance Species convened.


The NISA influenced state aquatic weed laws. It reauthorized the ballast program and established the Aquatic Nuisance Species Task Force. Some $30M was provided over 5 years through EPA research grants.


The Western Regional Panel on Aquatic Nuisance Species became active.


Enter the Gulf and South Atlantic Regional Panel on Aquatic Invasive Species


The NEANS Panel established.


Protect Your Waters campaign begins. Their electronic news continues.


Habitattitude campaign begins. Industry/consumer public awareness focus.


SAFETEA-LU adds eligibility to control aquatic weeds on Federal-Aid highway projects.


Midwest Natural Resources Group is asked to support the Great Lakes Commission effort to control invasive species.

Information from these references and experience:

For More Information:


  • Bossard, Carla C., John M. Randall and Marc C. Hoshovsky, 200. Invasive Plants of California's Wildlands. University of California Press, Santa Rosa.
  • Burrell, C. Colston, 2006. Native Alternatives to Invasive Plants. Brooklyn Botanic Garden, New York.
  • Czarapata, Elizabeth J., 2005. Invasive Plants of the Upper Midwest. University of Wisconsin Press, Madison.
  • DiTomaso, Joseph M. and Evelyn A. Healy, 2003. Aquatic and Riparian Weeds of the West. University of California, Davis.
  • Harper-Lore, Bonnie L., Maggie Johnson and Mark W. Skinner, 2007. Roadside Weed Management. U. S. Department of Transportation, Federal Highway Administration, Washington D.C.
  • Randall, John M. and Janet Marinelli, 1996. Invasive Plants, Weeds of the Global Garden. Brooklyn Botanic Garden, New York.
  • Uva, Richard H., Joseph C. Neal and Joseph M. DiTomaso, 1997. Weeds of the Northeast. Cornell University Press, Ithaca.


  • Aquatic Plant Information System, a PC-based information system operating under Windows, developed by the COE, Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180-6199.

Web Sites

Many state sites are available through conservation or agriculture departments as well as via task forces and invasive councils. Here are some of the regional and national sources of aquatic invasive information:

Greener Roadsides is a quarterly publication of the Federal Highway Administration, Office of Planning, Environment and Realty. If you would like to submit letters, comments, or articles please address them to:

Bonnie Harper-Lore
Editor, Greener Roadsides
Federal Highway Administration
Office of Natural and Human Environment
1200 New Jersey Avenue SE
Washington, DC 20590

Phone: (651)291-6104
Fax: (651)291-6000

All articles are advisory or informational in nature and should not be construed as having regulatory effect. Articles written by private individuals contain the personal views of the author and do not necessarily reflect those of FHWA.

Publication Number FHWA-HEP-08-022

Questions and feedback should be directed to Deirdre Remley (deirdre.remley@dot.gov, 202-366-0524).

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