Rare Plants 


NH Heritage maintains records on 386 plant species judged to be rare or imperiled in the state. The tracking list was developed in cooperation with professional and amateur botanists, conservation organizations, and other knowledgeable individuals. It includes the 288 species listed as endangered and threatened under the Native Plant Protection Act plus 98 others that are considered rare but do not have legal status. Plants tracked by NH Heritage are those with state ranks of S1 or S2. Some S3s are also tracked on a watch list (see Rarity & Ranking for detailed descriptions). Range-wide distribution maps, state and provincial ranks, and other information on the status of all plants and animals in North America can be found at the web site www.natureserve.org maintained by NatureServe.

List of Rare Plants -- List of Rare Plants and Animals by Town -- Other Lists

Carex rostrata sedge (photo by Dan Sperduto for the NH Natural Heritage Bureau) yellow lady's slippers (photo by Sara Cairns for the NH Natural Heritage Bureau) small whorled pogonia (Isotria medeoloides) (photo by Ben Kimball for the NH Natural Heritage Bureau)

Native Plant Protection Act

In 1987, the New Hampshire state legislature passed the Native Plant Protection Act (RSA 217-A) and formally recognized that "for human needs and enjoyment, the interests of science, and the economy of the state, native plants throughout this state should be protected and conserved; and . . . their numbers should be maintained and enhanced to insure their perpetuation as viable components of their ecosystems for the benefit of the people of New Hampshire." To compile a list of the species requiring protection, NH Heritage collaborates with knowledgeable botanists and identifies the most imperiled taxa as "endangered" and those likely to become endangered as "threatened." A total of 288 taxa are listed, 144 as endangered and 144 as threatened.

Categories of Plants

Plant species tracked or under consideration by NH Heritage can be divided into four categories.

1. Plants Listed as Endangered or Threatened. This category includes 288 species currently listed as endangered or threatened under the Native Plant Protection Act. Endangered and threatened are defined in the law as:

Endangered: Native plants with three or fewer natural occurrences in the state observed within the last 50 years, or plants with more than three occurrences which are, in the judgement of experts, especially vulnerable to extirpation.

Threatened: Native plants documented as having 10 or fewer natural occurrences within the last 20 years or that are otherwise threatened by extirpation due to habitat loss or other factors.

Four of these species are also listed as endangered or threatened under the federal Endangered Species Act. These plants are: Jesup’s milk-vetch (Astragalus robbinsii var. jesupii), small whorled pogonia (Isotria medeoloides), Robbin’s cinquefoil (Potentilla robbinsiana), and northeastern bulrush (Scirpus ancistrochaetus).

2. Candidates for Listing as Endangered or Threatened. This category contains 187 plants identified by a committee of experts as being apparently rare. The list includes species that (a) have 20 or fewer populations in the state, (b) show evidence of recent decline, or (c) have habitats that are seriously threatened. This category includes plants currently tracked by NH Heritage that have no legal status (98 taxa) plus other apparently rare species that warrant consideration for legal listing (89 taxa).

3. Plants in Need of Additional Expert Review. This category consists of 252 New Hampshire plants whose rarity status is less certain than those in the other two categories. These plants will require additional expert review as less information was readily available on their status. We developed this list by reviewing the state checklist compiled by Gilbert George (George 1997), and identifying those taxa that were uncommon or potentially rare based on the checklist and field observations by NH Heritage staff. We also identified species listed in Kartesz (1999) as occurring in New Hampshire but are not included in George (1997). Many of these apparently new records for the state would be rare in New Hampshire, but require further verification before being officially considered for listing.

The overall list of species requiring additional review certainly contains many plants that are not rare in the state. However, it also likely contains species that are rare but have been overlooked. Additional expert review should considerably reduce the number of species on this list, leaving those that are truly rare and yielding a more biologically and taxonomically accurate list of New Hampshire’s rare plants.

4. Plants Listed as Special Concern. In addition to recognizing "endangered" and "threatened" plant species, the NH Native Plant Protection Act identifies 9 plants as "special concern." These species are somewhat uncommon in New Hampshire, and are at risk of decline due to over-collection. The NH Natural Heritage Bureau does not track these species, nor do we seek locational data for them:

Narrow-leaf wild leek (Allium tricoccum var. burdickii)
Wild leek (Allium tricoccum var. tricoccum)
Wild ginger (Asarum canadense)
Giant blue cohosh (Caulophyllum giganteum)
Blue cohosh (Caulophyllum thalictroides)
Sea lavender (Limonium carolinianum)
Ostrich fern (Matteuccia struthiopteris var. pensylvanica)
Canadian burnet (Sanguisorba canadensis)
Slippery elm (Ulmus rubra)

Taxonomic Status, Nomenclature, and Synonymy

Our nomenclature and taxonomic treatment of New Hampshire plants follow the Flora of North America Editorial Committee (1993a, 1993b, 1997) when available, and then primarily Kartesz (1999). For all plants in New Hampshire, we have matched the nomenclature used for the current endangered and threatened plants with a list of synonyms based on Kartesz (1999), references compiled in George (1997), and regional floras including Fernald (1950), Gleason and Cronquist (1991), Voss (1972), and Flora of North America Editorial Committee (1993a, 1993b, 1997).

Uvularia grandiflora (large-flowered bellwort) in bloom in a patch of rich mesic forest
in Plainfield (photo by Ben Kimball for the NH Natural Heritage Bureau).