Invasive Plants

Plant Invaders

Invasive plants are non-native species that are capable of moving or, more likely, being moved into a habitat and then monopolizing resources such as light, nutrients, water, and space at the expense of and to the detriment of other species. They are more aggressive and successful than native species at dominating the available resources.

Invasive Plants in the Lake Champlain Basin

  • hydrilla


    Hydrilla (Hydrilla verticillata): is a highly aggressive plant. Hydrilla has clogged drainage canals in the southeast and it’s been reported as close as Massachusetts, Maine, and southern New York. Fragments falling from boats, trailers, and live wells can start new populations, which often begin near boat launches.Hydrilla was first introduced to the United States as a popular aquarium plant, which was then accidentally released into the wild in Florida. Hydrilla is capable of completely clogging waterways. Its vertical branches often out-compete native plants, affecting water quality and restricting flow. The widespread growth of this plant has dramatic impacts on recreational uses such as boating, fishing and swimming.Compared to other aquatic plants, Hydrilla grows well in deeper, darker waters and new infestations may establish a foothold there before spreading into shallower waters and out-competing other resident plants..



Eurasian Milfoil

  • Eurasian Water milfoil (Myriophyllum spicatum), first discovered in the Basin in 1962, is found in many areas throughout the Lake and Basin. In some areas infestations are severe. Detailed watermilfoil studies have been conducted for many of Lake Champlain’s bays and for 35 other lakes within the Basin, but many areas have little or no study regarding the presence and extent of infestation. Because Eurasian water milfoil is spread by plant fragments transported by waves, wind, currents, people, and to some extent, animals, it is not easily controlled.



  • Variable-leaved Milfoil (Myriophyllum heterophyllum) : Related to Eurasian Water milfoil was found in 2009 in Missisquoi Bay; it too can become a nuisance. Because milfoil spreads by stem pieces, roots and seeds, plant parts can easily hitchhike on recreational equipment if not removed. Boaters are advised to avoid beds of watermilfoil to prevent spreading the plant further. Boaters, anglers and other recreational enthusiasts should take precautions to avoid transporting this and other invasive species to other waters or other parts of Lake Champlain.


  • Japanese Knotweed

    Japanese Knotweed

    Japanese knotweed (Polygonum cuspidatum) was first introduced to the United States as an ornamental plant in the late 1800’s for its appealing flowers. It was also used for erosion control because of its prolific growth. It has since spread into the wild across the United States, including the Lake Champlain Basin. It spreads by underground rhizomes that easily fragment and spread to other areas. This is a problem especially along stream banks where natural forces contribute to the spread of knotweed.

Japanese knotweed has already altered the natural characteristics of the Lake Champlain Basin. Since it grows early in the season and is very dense, it excludes the growth of native plant species. When dense stands are removed from river banks there can be increased erosion until native plants are able to reestablish themselves.


  • European Water Chestnut

    European Water Chestnut

    European water chestnut (Trapa natans), first documented in Lake Champlain in the 1940s, displaces other aquatic plant species, is of little food value to wildlife, and forms dense mats that change habitat and interfere with recreational activities. Water chestnut is a fierce competitor in shallow waters with soft, muddy bottoms. Uncontrolled, it creates nearly impenetrable mats across wide areas of water. In South Lake Champlain, many previously often fished bays are now inaccessible and floating mats of chestnut can create a hazard for boaters. This noxious plant also blocks light into the water, a critical element of a well-functioning aquatic ecosystem, reduces oxygen levels which may increase the potential for fish kills.

Submersed leaves are feather-like; each leaf is divided into segments that are whorled around the leaf stem. White flowers form in the axils of the surfacing leaves in July. Fruit are nut-like and “woody” with typically four sharp, barbed spines. Long cord-like rarely branching stems can attain lengths of up to 16 feet. Water chestnut grows in freshwater lakes and ponds and slow moving streams and rivers. It prefers calm, shallow, nutrient-rich waters.

  • Invasive Plants Didymo

    Didymo or ‘Rock Snot’

    Didymo: Didymosphenia geminata, commonly referred to as “didymo” or “rock snot” is a freshwater algae. Native distribution of the species includes cool temperate regions of Northern Europe and Northern North America. While not much of a threat to Lake Champlain itself, didymo may pose a threat to rivers and streams because it can form dense mats in stream beds. Scientific studies conducted around the world have yet to show that didymo has significant impacts to salmon and trout.

    Didymo attaches to the streambed by a stalk. It has a rough texture similar to wet wool and mimics strands of toilet paper, as opposed to other species of algae which feel slimier.

    Didymo can be accidentally spread by people using rivers, as its microscopic cells can cling to boats, waders, fishing gear, sandals, and anything else that comes in contact with water. Gear must be dried for a minimum of 48 hours or cleaned with a bleach solution to get rid of the algae.


What else poses a threat to Lake Champlain’s ecosystem?

Next: Are There Other Invasive Threats to Lake Champlain? ( Next >> )

Previous:  Invasive Invertebrates ( << Previous )