Plants become rare for different reasons. Plant numbers can decrease due to factors, such as climatic changes and geographical shifts, according to the New York Natural Heritage Program, which seeks to educate people about rare plants and encourages observation of remaining specimens. However, humans threaten most plants, particularly via pollution, spreading development that wipe out habitats and introduction of non-native plants.
Pink Sand Verbena
This perennial herb is listed by the California Native Plant Society as seriously endangered in the state. Its natural habitat is on coastal dunes in the northern half of the state, where it blooms from June through October. This low-growing plant has wiry, hairy stems and clusters of small flowers. Vehicles, invasive plant species and pedestrian traffic have contributed to its rarity.
Western Prairie Fringed Orchid
This Midwestern prairie plant is a federally threatened wildflower that grows in seven states and parts of Canada, most often in remnant upland prairies and sedge meadows, but also in disturbed sites. The Lewis and Clark Expedition first documented it. It features white, fringed flowers that appear in clusters and include light green sepals. This perennial can grow up to 4 feet tall. Evolving agricultural uses have restricted its growth.
Northern Wild Monkshood
This delicate, perennial flower is federally threatened and is now only found in Ohio, Iowa, New York and Wisconsin. It grows along moist, shady, rocky cliffs and in crevices near streams. Its flowers are hood-shaped, light blue, about 1 inch long and appear along the length of taller stems that grow up to 4 feet tall. Contamination and filling of sinkholes, grazing and trampling by livestock, human foot traffic, logging, quarrying and other factors have reduced this species.
Decurrent False Aster
This federally threatened species has small, white daisy-like flowers with yellow centers. It thrives best in areas that periodically flood because other competing species are then swept away, according to the U.S. Fish and Wildlife Service. Today, it is mainly found on moist, sandy lowlands and prairie wetlands, particularly along the Illinois River. The Service states excessive silting from agricultural practices may be to blame for this species' decline. Habitat destruction from levy construction and other activities that have changed water movement patterns are also credited.
Dwarf Lake Iris
Deep blue flowers that measure up to 1-½ inches in width and grow on stems that are up to 2 inches tall characterize the dwarf lake iris, which is a federally threatened species. This low-growing perennial only grows around the Great Lakes shores of Lakes Huron and Michigan. It prefers cool, moist lakeshore air and loose, sandy soil covering gravel or bedrock. Shoreline development has greatly reduced its growth. This species is sometimes sold commercially. Relocating or picking wild specimens could adversely affect the species, and could violate laws.