skip navigation
New Hampshire Department of Environmental Services


The NHDES Exotic Species Program coordinates activities associated with the control and management of exotic aquatic plants, as well as activities associated with the implementation of education programs and volunteer plant monitoring programs.

The program, initiated in 1981, has five focus areas: 1) Prevention of new infestations, 2) Monitoring for early detection of new infestations to facilitate rapid control activities, 3) Control of new and established infestations, 4) Research towards new control methods with the goal of reducing or eliminating infested areas, and 5) Regional cooperation.

Exotic aquatic plants, such as milfoil and fanwort, have been a problem in New Hampshire lakes and ponds since the mid-1960s. Variable milfoil, by far the most wide-spread exotic aquatic plant in NH, was first found in Moultonborogh Bay in Lake Winnipesaukee. From there it has spread to infest more than 60 waterbodies. The program works mostly with submerged exotic aquatic plants, including variable milfoil (Myriophyllum heterophyllum), Eurasian milfoil (Myriophyllum spicatum), fanwort (Cabomba caroliniana), Brazilian elodea (Egeria densa), Hydrilla (Hydrilla verticillata) and water chestnut (Trapa natans), among other species. Other exotic plants, such as common reed (Phragmites australis) and purple loosestrife (Lythrum salicaria), although also of concern, are not addressed by the Program because they are not submerged aquatic plants, and are generally found more often in wetlands than in lakes or ponds.

Why are these plants such a problem? Native plant communities have evolved together over hundreds of years. Animal and insect grazers have become specialized to feed on these native plants. Since exotic plants are introduced from outside of the state, they have no established relationships with native fauna that would keep their growth in check. When these exotic plants grow without natural controls they encroach into and replace the habitats of native plants, disrupting the food chain, stunting fish growth and degrading wildlife habitat. Waterbodies with exotic plant infestations in New Hampshire are considered impaired for aquatic life support.

Other states besides NH are also faced with the problem of exotic plants, and unfortunately, no one has yet found a practical, ecologically sound means of eradication for these plants. Once in a waterbody, continuous management and control practices are the only tools to control the nuisance plant growth.

It therefore becomes increasingly more important to prevent infestations, and to identify new infestations early. NHDES biologists conduct numerous field investigations each summer, but with over 800 lakes and ponds in the state, the efforts of volunteers in monitoring waterbodies for new infestations become critical. Through materials and training sessions by NHDES, numerous lakes and ponds have initiated their own Volunteer Weed Watching programs.

For more information about exotic species, please contact the Exotic Species Coordinator at (603) 271-2248 or

  • Amy P. Smagula
    Limnologist/Exotic Species Program Coordinator
    NH Department of Environmental Services
    29 Hazen Drive; PO Box 95
    Concord, NH 03302-0095
    (603) 271-2248
    (603) 271-7894 (fax)

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

copyright 2017. State of New Hampshire