This is a list of native vascular plant species in Maine whose populations within the state are highly vulnerable to loss, including species determined to be Endangered, Threatened, and of Special Concern. Species on the list are typically known from a very small number of sites within the state, and many require unique habitat for survival. This list is used to assist scientific research, environmental assessment, permit review, land management, and for educational purposes. This list is managed by the Maine Natural Areas Program (MNAP). The Official List of Endangered and Threatened Plants (a subset of this list) is under the jurisdiction of the Commissioner of the Department of Agriculture, Conservation and Forestry. Downloadable Rare Plant Fact Sheets are available for many listed species.
Rare Plant FAQs
How do we know which of Maine's native plants are rare?
The rarity of plant species in Maine has been established through a rigorous process of historical research, field surveys, and evaluation by professional and amateur botanists and ecologists. Botanists have been documenting the distributions of plants within the state for nearly 150 years. They have collected tens of thousands of plant specimens and deposited them in university herbaria or in private collections. These records are carefully reviewed, results of the review are shared with the state's active botanical community, and the Botanical Advisory Group is convened to complete an evaluation of each proposed species. Evaluations are based on a set of criteria of plant biology that contribute to species rarity. As of the most recent revision of the list, the biological criteria for rarity have been formalized into the following seven categories:
- Endemism - geographically restricted to the State or areas immediately adjacent to the State.
- Few Populations - extremely small number of populations.
- Few Individuals - numerically scarce, small number of individual plants.
- Special habitat - requiring habitat that is scarce in the State.
- Limit of range - edge of distribution or disjunct from main distribution.
- Population declining - seriously declining due to habitat modification or destruction, or from over collection for commercial, recreational, or educational purposes.
- Population vulnerability - highly vulnerable to decline due to location or human usage.
How does MNAP keep the Official List of Endangered and Threatened Plants in Maine up to date?
The list is kept up to date through a process of periodic review. The Botanical Advisory Group reviews each species and modifies its status based on the most recent population numbers and the established criteria. Changes to the list are based on new botanical inventory information and on recent taxonomic studies. A biennial update of the list enables various users to have the most current information when conducting field surveys, performing environmental assessments, or in conducting biological research. Justifications for listings and all supporting data are maintained within the Biotics data system at the MNAP.
What is Elements of Natural Diversity: Rare, Threatened, and Endangered Plants?
In addition to the Official List of Endangered and Threatened Plants in Maine, MNAP also maintains the state's tracking list of rare plants (Elements of Natural Diversity: Rare, Threatened, and Endangered Plants). The state's tracking list includes all plants listed as Endangered and Threatened as well as other groups including those listed as Special Concern and Possibly Extirpated. The state's tracking list is considered the working list for data collection on Maine's rare plant species. MNAP is interested in obtaining data on populations of all species found on the tracking list.
What are the definitions of rarity?
- Rare and in danger of being lost from the state in the foreseeable future, or f ederally listed as Endangered.
- Rare and, with further decline, could become endangered; or federally listed as Threatened.
- Special Concern
- Rare in Maine, based on available information, but not sufficiently rare to be considered Threatened or Endangered.
- Possibly Extirpated
- Not known to currently exist in Maine; not field-verified (or documented) in Maine over the past 20 years.
Please refer to the Rarity Ranks Explanation page for more information
Is this Lady's-slipper rare?
Please see our Lady's-slippers in Maine information page for more information about which lady's-slippers are rare in Maine.