Plants are rare and imperiled in New Hampshire for a variety of reasons.
Some are naturally rare, having normally low population numbers or growing in unusual habitats. Some species were historically uncommon yet stable, but habitat alterations by humans have reduced their population numbers. Today, the dunes are almost completely developed, and the hairy hudsonia s decline reflects the elimination of its habitat. Many of New Hampshire s imperiled plants are rare in New Hampshire but common elsewhere, usually because New Hampshire is on the edge of the species range. Our ranking system allows us to distinguish between species that are locally and globally rare versus those that are rare in New Hampshire but are globally more common.