Saving Imperiled Plants

A Fifth of Our Native Plant Species Are in Danger

This is how we're working to save them

New England's rare plants are in peril, and we are at the forefront of global efforts to save rare plants from extinction. We're banking their seeds to preserve genetic diversity and to ensure their survival in the face of multiple threats. At the same time, we're restoring populations of the most at-risk species, monitoring populations of rare plants in every county in New England, and documenting the health of the 3,300 populations of our 389 globally and regionally rare plants.

Our field research provides the data for our scientific publications, including our Conserving Plant Diversity in New England (see below) and State of the Plants reports, Flora Conservanda New England, and conservation and research plans for 117 of New England's rarest species. Please see below to download the reports.

Conserving Plant Diversity in New England - Report and Interactive Mapping Tool

New England's climate-resilient areas with abundant rare species offer a key conservation opportunity.

Conserving Plant Diversity in New England is a groundbreaking report resulting from a two-year collaboration between Native Plant Trust and The Nature Conservancy. Released in 2022, the report provides a scientific framework and detailed roadmap for conservation action and land protection at the species, habitat, and parcel scales that can save plant diversity—and thus overall biodiversity—in New England as the climate changes.

The report analyzes whether more than a century of conservation has protected enough land in the right places to save the region’s plant diversity. It concludes that we need to conserve another 2.3 million acres of climate-resilient land in specific habitats, and it identifies which areas are priorities in each of the six New England states.

For the first time, this report delineates 234 Important Plant Areas containing exceptionally high rare plant diversity and then examines how much of those areas and each of the region’s 43 primary habitats are:

protected for nature and natural processes
secured from conversion to another land use, but open to activities like logging and mining
threatened by development
resilient to climate change.

The results are measured against important benchmarks in the UN’s Global Strategy for Plant Conservation and in the Global Deal for Nature. The latter calls for protecting 30 percent of the world’s ecosystems by 2030 and is the basis for the worldwide “30 by 30” initiative recently embraced by the Biden administration.

Combined with a robust mapping tool, this technical report gives policy makers, federal and state agencies, and land trusts in each state the detailed information needed to most effectively spend their conservation dollars.

The report’s interactive maps and state-specific data enable policy makers, federal and state agencies, and the land trusts to conserve the IPAs in each state, which will save rare species across multiple habitats.

Download the full report here.

Download the report by section:

A Species on the Edge

How does a plant survive in rock crevices scoured by frigid torrents?

High-energy river systems are some of the most dynamic habitats in New England. As spring arrives, the winter’s ice retreats, and flood waters and ice blocks move down rivers with incredible power, scouring the shorelines and sometimes taking out bridges along the way. Yet a surprising number of rare plant species make their home along these rivers, including the globally rare Jesup’s milk-vetch (Astragalus robbinsii var. jesupii), which grows in only three places in the world, all of which lie along a 16-mile stretch of the Connecticut River in Vermont and New Hampshire.

Jesup’s milk-vetch grows in the thin pockets of soil deposited on the rugged ledges of the riverbank. The plants bloom in late May or early June, and, like many species in highly disturbed environments, reproduce primarily by seed. Flooding can occur at any time during the growing season, and this species’ survival tactic seems to be to try to seed itself around as much as possible, increasing the chances that some offspring can find a suitable spot to germinate.

This species seems to behave primarily as a short-lived perennial, with the adults often dying after bloom, usually in their third year. Intensive monitoring, led by Native Plant Trust's Conservation staff, began in the late 1990s. Since that time we have recorded a gradual increase in temperatures on all the sites. Though the phenology is still largely synchronized with the river's flooding and ice scouring, rising temperatures and more precipitation could prompt the overhanging canopy to leaf out earlier, and Jesup's milk-vetch seedlings could be shaded just when they need sun. Invasive species are also posing a threat. In 1986, when botanists first collected seeds of Jesup’s milk-vetch to bank, the field records do not mention any invasive plants sharing its habitat. Today, several invasive species grow on the rugged ledges.

Because of these threats, our Conservation staff, in collaboration with the US Fish and Wildlife Service, New Hampshire Natural Heritage Bureau, and Vermont Natural Heritage Inventory, is attempting to remove invasive species, augment existing populations, and introduce plants on sites that appear to contain suitable habitat. Initial attempts to augment existing populations with plants propagated in our nursery were only marginally successful. Over time, however, more of the transplanted seedlings are surviving, blooming, and setting seed.

During the past eight years, the team has successfully introduced plants in five places that are not part of the known historic range. Not only have our transplanted seedlings survived here, but new seedlings have also popped up—the birth of a new population. Other introduced populations are also surviving.

In 2020, the US Fish & Wildlife Service provided funding for us to conduct a more definitive genetic analysis of Jesup's milk-vetch populations at each of the three natural sites and one introduction site. The most significant takeaway of the analysis is that the three populations are genetically distinct, indicating that each population is uniquely adapted to its environment and therefore is at risk of local extirpation. For this reason alone, genetic analysis is crucial for any future introductions as well as ongoing augmentation.

A Matter of Sunlight—but How Much?

Long-term research on a rare forest orchid

Since 1988, the Conservation staff has monitored a patch of small whorled pogonia (Isotria medeoloides) at an experimental site on private land in New Hampshire.The experiment consists of thinning the canopy in varying degrees to admit different levels of light to the floor of the mixed conifer and hardwood forest where this delicate yellow orchid grows. Because Isotria has never been successfully transplanted, the goal is to understand how to maintain it in its natural habitat.

Director of Conservation Emeritus Bill Brumback led the experiment from its inception, after obtaining permission from the private landowner. "Over time, we have found that giving this species more light increases both the plant’s numbers and its flowering," he explains. (Because botanists don’t yet know how many seeds these plants produce, or how many germinate, the experiment uses flowering as a proxy measurement of reproduction.)

Brumback says that this finding means that if this or other Isotria habitat were formally conserved, land managers could preserve the orchids simply by thinning the canopy over them. "And, because these plants continue to proliferate beneath the sections of the canopy cut in 1998 and not thinned since then, we might not need to thin very often," he says.

Over the past two years, however, the number of Isotria stems emerging beneath the canopy has declined slightly since the initial thinning. Further monitoring, says Brumback, will reveal whether this represents a true decline, possibly due to the denser canopy, or a normal variation. Such is the nature—and the luxury—of long-term observations of a single population of rare plants.

Flora Conservanda New England

The only comprehensive list of plants in need of conservation in our region

Flora Conservanda 2012 was prepared by our staff and our colleagues in the New England Plant Conservation Program. It documents plants growing in our region that are rare globally, regionally, and locally. It also lists plants that are considered historic in New England (though they may exist elsewhere in the U.S. or the world) and plants whose status in the region was undetermined at the time but believed to be rare. Download Flora Conservanda 2012.

The 2012 list is a revision of the original document, published as the 1996 edition of Rhodora, the journal of the New England Botanical Club. We revised the list for 2012 based on research accumulated over the preceding 15 years, including taxonomic studies and field research by professionals and volunteers. We added species based on their rarity in the wild, and we removed others because we learned that they are more common than previously understood, or else our taxonomic understanding of the species changed so that it is no longer considered rare in New England.

We view the 2012 list as a snapshot of plant rarity in New England at that time. Information such as the number of extant populations, state rarity ranks, and endangerment codes may no longer be current. For more recent data, please consult the latest state endangerment status and state ranks on Heritage Program websites.

In 2014, we published an article in Rhodora analyzing the changes revealed between 1996 and 2012. Download the Rhodora article.

Conservation and Research Plans

More than 140 expert authors and reviewers contributed to this comprehensive series of Conservation and Research Plans for 117 of New England's rarest plants.

We designed these plans for a variety of users: Government agencies, volunteers and interns, private landowners, and anyone else who wants to help rare plant species to recover.

Each plan includes: