Non-Native Invasive
Aquatic and Wetland Plants
in the United States

A joint project of Sea Grant and other offices of
the University of Connecticut, University of Florida, University of Minnesota,
University of Illinois, North Carolina State University and Purdue University

National Invasive Aquatic Plant Outreach and Research Initiative

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What's the problem?
The Sea Grant 22
State plant laws and lists
Buying mail-order plants
What can I do?
More non-native plants...
About This Sea Grant Initiative...

twenty-two of the most worrisome non-native invasive aquatic and wetland plants that are already inside, or that could enter, the United States.

This web site is part of the University of Florida APIRS web site; was developed by workers of several universities; and was funded by National Sea Grant.

Natural areas of the U.S., including the country's lakes, rivers, marshes and swamps, face trouble.

One source of trouble is the quickly-spreading problem of non-native invasive aquatic and wetland plants, plants that can and do spread into and infest the watery ecosystems of the United States.

All plants evolve with natural growth checks that help keep plant populations in balance, "checks" such as fungus, bacteria and ordinary plant diseases; fish and other animals; climate; geology, etc. All play their part in Nature's balancing act. In a balanced ecosystem, variety reins. In a balanced ecosystem, there is a biodiversity of plants, growing and evolving.

However, when a non-native plant, a species that evolved someplace else, is introduced into new areas, it usually does not have its natural growth checks. So, often enough, the non-native plant is able to grow wildly, quickly covering, smothering and replacing the plants that were naturally there in the first place. The non-native plant may form an exotic monoculture (where no other plants grow).

Naturally, we want our own native plants, beautifully unique, not to be replaced by somewhere else's beautifully unique plants.

This scientific article from 1989 is a very thorough examination of the processes of invasions by aquatic plants, written by two of the world's most respected investigators on the subject.

Here is a thought-provoking perspective on "non-native plants" from an evolutionary biologist. It is an article from Nature and Ideology: Natural Garden Design in the Twentieth Century, ed. Joachim Wolschke-Bulmahn (Washington, D.C. Dumbarton Oaks, 1997). This is a link to an off-site PDF file; accessed with permission.

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Non-native aquatic invasive plants also can jam turbines and dams; fill up canals and ditches; cover fish-spawning, bird-nesting areas and turtle-laying areas; and interfere with and even prevent fishing, swimming, and boating, even including large commercial boats. Non-native plant infestations even reduce property values.

In addition, stands of non-native plants usually are not useful to the nation's wildlife. Native wildlife has evolved to be dependent on native plants for food and shelter. Only sometimes are native animals able to adapt to newly introduced, non-native plants. Should non-native plants replace too many of our native plants, those animals that are dependent on native plants will move away or even perish (become extirpated).

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Worth remembering! Their plants somehow get here, and our plants somehow get there. Our own benign beloved plants, when introduced to other areas, often become their invasive plants, plants to curse and have meetings about. These are global problems. For a bit more information about the global aspects of plant invasions, see this AQUAPHYTE article.

Government agencies are marshalling their resources, spurred by a Presidential Executive Order. And a National Management Plan has been published by The National Invasive Species Council. However, citizens also must play their part; here's what you can do.

Because we all want to preserve our own pieces of paradise, there is tremendous interest in identifying and controlling non-native invasive plants before they grow, spread, and have irreversible effects on our lands and waters.

That's where this web site comes in. For each of the plants listed below, we review as much information as is known, based on the scientific literature as found in APIRS, the world's largest collection of primary information about invasive aquatic and wetland plants.

In this Sea Grant project, we focus on twenty-two of the most invasive aquatic and wetland plants which are affecting, or could affect, the United States, as determined by an expert steering committee. Unfortunately, there are many more such plants; we hope to have them included here in the future.

Butomus umbellatus - flowering rush

Cabomba caroliniana - fanwort
Caulerpa taxifolia - caulerpa marine alga
Egeria densa - Brazilian elodea, Brazilian waterweed
Eichhornia crassipes - water hyacinth
Hydrilla verticillata - hydrilla, water-thyme
Hydrocharis morus-ranae - European frog's-bit
Hygrophila polysperma - East Indian hygrophila, Indian swampweed
Ipomoea aquatica - water spinach, swamp cabbage
Iris pseudacorus - yellow flag, pale yellow iris
Lagarosiphon major - African elodea
Limnophila sessiliflora - ambulia, Asian marshweed
Lythrum salicaria - purple loosestrife
Melaleuca quinquenervia - melaleuca
Myriophyllum aquaticum - parrot feather
Myriophyllum spicatum - Eurasian water milfoil
Nymphoides peltata - yellow floating heart
Pistia stratiotes - water lettuce
Potamogeton crispus - curlyleaf pondweed, curly pondweed
Salvinia molesta - giant salvinia, Kariba-weed
Spartina alterniflora - salt marsh cordgrass, saltwater cordgrass
Trapa natans - water chestnut

Many states have their own laws, lists, rules and regulations regarding non-native plants. Do you know what yours are?

There are more non-native plants elsewhere on this APIRS web site. Click on those marked Non-Native.

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Non-Native InvasiveAquatic and Wetland Plantsin the United States

Non-Native Invasive
Aquatic and Wetland Plants
in the United States