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Invasive Species Frequently Asked Questions

Frequently asked questions regarding invasive species in New Hampshire.

What are invasive species?

What is the Invasive Species Committee?

What are the criteria used to determine which species warrant prohibition in New Hampshire?

Which terrestrial (upland) plants are considered invasive in New Hampshire?

Which aquatic (those that occur in surface waters) species are considered invasive in New Hampshire?

Why are landscape plants such as Norway maple, Japanese barberry, and Burning bush considered invasive in New Hampshire?

What regulations apply to invasive species in New Hampshire?

What is the state doing to educate the public?

back to topWhat are invasive species?

Throughout the United States and Canada, non-native invasive species have become an overwhelming problem resulting in impacts to the natural environment and managed landscapes. Invasive species typically possess certain traits that give them an advantage over most native species. The most common traits include the production of many offspring, early and rapid development, adaptability and tolerance of a broad range of
environmental conditions and, the lack of natural controls to keep them under control. These traits combined allow certain non-native species such as Oriental bittersweet - Celastrus orbiculatus, Japanese barberry - Berberis thunbergii, and others to become highly competitive and dominant in many of New Hampshire's natural and artificial landscapes. In some instances the sheer density of an invasive species like Purple loosestrife - Lythrum salicaria, within a wetland ecosystem can affectively result in the loss of native flora and fauna normally found occupying those habitats. Other species as Norway maple - Acer platanoides or Tree of heaven - Ailanthus altissima rely on their ability to excrete toxic chemicals from their roots (called Allelopathy) that interfere with or prevent the establishment of native species within its rooting zone. Furthermore, studies have shown that invasives can reduce natural diversity, impact endangered or threatened species, reduce wildlife habitat, create water quality impacts, stress and reduce forest and agricultural crop production, damage personal property, and cause health problems. Within the United States, the adverse economic impacts resulting from invasive species currently exceeds $100 billion annually. Unfortunately, New Hampshire is not immune, every community in the state is currently impacted by at least one invasive plant and as the number of invasive populations grow so does the potential for greater dispersions. In an effort to counteract these adverse effects, the New Hampshire Department of Agriculture, Markets & Food (DAMF) has been given the authority (RSA 430:51) to create rules (Agr 3800) and regulations to preserve and protect the states economic integrity and ecological stability.

back to topWhat is the Invasive Species Committee?

The Invasive Species Committee (henceforth referred to as the ISC) is a volunteer group of eleven appointed members who meet on a routine basis to address invasive terrestrial (those that occur in uplands, not surface waters) plants, insects, and fungal species and their effects upon the state and its natural and economic resources. The efforts of the ISC include, but are not limited to the following: prepare and publish a list of Prohibited Invasive Species and a list of Restricted (Watch) Invasive species; establishing means by which that state shall minimize such adverse effects; promote research and educational activities so as to achieve the best possible protection of agriculture, forest, wildlife, and other natural resources of the state and of human health; and to prevent and control the spread of invasive species in the state (refer to RSA 430:51 through RSA 430:57).

back to topWhat are the criteria used to determine which species warrant prohibition in New Hampshire?

The ISC utilized, until recently (2013) a set of criteria for the evaluation of plants (see 1 below) and insects (see 2 below), to determine if a specific species (including all of its associated cultivars and varieties) warrants listing as a prohibited invasive speciespdf file. The species selected for evaluation are the result of a compilation of plants or insects found on other invasive species lists in other states and Canada which have similar growing conditions as New Hampshire. Plants that have been evaluated but did not meet the criteria can be found on the New Hampshire Restricted list (New Hampshire's Restricted List.pdf) (also referred to as the Watch List). The Restricted list is maintained as a requirement of the law, but currently there are no rules or regulations associated with the plants found on this list. As a note, fungi have not been evaluates as of yet, but will at a later date). The plant and insect criteria are as follows:

1. Criteria for Prohibited Invasive Plants in New Hampshirepdf fileand;
2. Criteria for Prohibited Invasive Insects in New Hampshirepdf file

As of 2013 the ISC has adopted the nationally recognized invasive species evaluation protocol known as NatureServe Invasive Species Impact Rank (I-Rank). It is used to determine which non-native plant species pose the most serious threats to native species and ecosystems. to make the assessment process objective, transparent, and systematic. It is intended to be applied to non-native plants as they occur over a large area, such as a nation, ecoregion, province, or state.

The protocol is used to assess non-native plant species individually for a specified region (e.g., the 50 US states) and to assign each an Invasive Species Impact Rank (I-Rank) of High, Medium, Low, or Insignificant to categorize its negative impact on natural biodiversity within that region. The protocol includes 20 questions grouped into four sections: Ecological Impact, Current Distribution and Abundance, Trend in Distribution and Abundance, and Management Difficulty. The answers to the questions within each section are used to calculate a subrank for that section, and an overall I-Rank is then calculated from these subranks. Text comments and citations to information sources are required to document the answers selected. If information (as evidenced by protocol questions answered) is sufficient to eliminate at least two of the four possible I-Ranks, but insufficient to narrow the I-Rank to a single value, a range I-Rank (e.g. High/Medium) is assigned. An I-Rank of Unknown is assigned when an attempt has been made to assess the species, but it was not possible to eliminate at least two of the four possible I-Ranks.

back to topWhich terrestrial (upland) plants are considered invasive in New Hampshire?

For a list of prohibited invasive plants, refer to the Prohibited Invasive Species Fact Sheet.pdf file

back to topWhich aquatic (those that occur in surface waters) species are considered invasive in New Hampshire?

Aquatic exotic/invasive species are not regulated by the Department of Agriculture Markets & Food, but rather fall under the Department of Environmental Services (DES), Limnology Division. The DES 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. Refer to the Aquatic Exotic Program website for rules and regulations.

back to topWhy are landscape plants such as Norway maple, Japanese barberry, and Burning bush considered invasive in New Hampshire?

Although these species have traditionally been heavily used for ornamental landscapes, they unfortunately possess all of the characteristics attributed to "invasive species". There are very few regions of New Hampshire where Norway maple, Japanese barberry and Burning bushpdf filehave not been found invading natural woodland areas.

back to topWhat regulations apply to invasive species in New Hampshire?

The New Hampshire Department of Agriculture, Markets & Food has oversight of the invasive species rules (Agr 3800). The rules were adopted in 2004 and were since revised in 2008. Essentially nobody is allowed to collect, import, transport, sell, propagate, transplant or cultivate any species (including all cultivars and varieties) of those species listed on the "New Hampshire Prohibited Invasive Species List" (Although the rules took effect in 2004 an exception was granted for the nursery industry to recoup their costs associated with Norway Maple, Burning Bush and Japanese Barberry by allowing a 3-year phase-out. This exception ended on January 1, 2007).

back to topWhat is the state doing to educate the public?

The Department of Agriculture, Markets & Food is very active in its efforts to educate the general public, conservation commissions, municipal and state highway departments, town administrators, and others. Douglas Cygan, Invasive Species Coordinator conducts in-depth PowerPoint presentations upon request geared toward a broad range of individuals. The presentation typically ranges from 1.5 to 2 hours and is often modified to be relative to the surrounding area where the presentations are held. To request a presentation please contact Mr. Cygan at (603) 271-3488 or by email at

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NH Department of Agriculture, Markets and Food
Mailing: PO Box 2042, Concord NH 03302 -2042
Physical: 25 Capitol Street, Second Floor, Concord, NH 03301
(603) 271-3551 | fax: (603) 271-1109