Canaan Valley (hereafter, the Valley) is a 34,600-ac (14,000-ha), high-elevation valley in the Central Appalachian Mountains of West Virginia. Its diverse wetland and upland habitats support a wide variety of plant communities, many of which are extremely rare. The prominence of rare communities is associated with the diversity of topographic settings, soils, geology, and hydrology, as well as the effects of human settlement and resource exploitation. Most of the rare plant communities are found in the wetlands of the Valley's floor. Virtually all of the communities associated with the Valley's extensive cold peatlands are rare, including (1) mixed conifer swamp-forests of Picea rubens (Red Spruce), Abies balsamea (Balsam Fir), and Tsuga canadensis (Eastern Hemlock), (2) mixed conifer-Fraxinus nigra (Black Ash) bog-forests in limestone-influenced wetlands in the central and southern parts of the Valley, and (3) extensive Sphagnum and Polytrichum bogs in the central and northern parts of Canaan Valley. Shrub communities such as Alnus incana ssp. rugosa (Speckled Alder), Viburnum recognitum (Smooth Arrowwood), and Salix discolor (Glaucous Willow) growing on mineral soils along waterways are also rare. Populus tremuloides (Trembling Aspen) groves, although abundant in the Valley, are extremely limited in the Appalachian region. Lastly, the grassand forb-dominated grass-bald communities on the surrounding mountain rims show an extremely limited distribution throughout the Central Appalachians.