Bedrock glades are xeric, sparsely vegetated, non-vertical bedrock exposures, with thin, often discontinuous soils. The rock types vary from quartzite (Baraboo Hills, McCaslin Mountain), to basalt (lower St. Croix River valley), to granite (northeastern Wisconsin). The flora can include prairie, savanna, or barrens components, some of them reaching their northern range limits in this community type, as well as bare rock specialists. Tree and shrub cover is usually sparse, and often has structural similarities to a thinly timbered savanna or woodland habitat. Important woody species may include pines (Pinus spp.), oaks (Quercus spp.), hickories (Carya spp.), and cherries (Prunus spp.), along with dogwood (Cornus spp.), hazelnuts (Corylus spp.), prairie willow (Salix humilis), and ericads such as huckleberry (Gaylussacia baccata). Xerophytic pteridophytes such as rusty woodsia (Woodsia ilvensis), northern fragile fern (Salix humilis), and rock spike-moss (Selaginella rupestris) are characteristic plants, as are lichens and mosses. Glades have apparently served as refugia for light- demanding species that are adapted to the more open savanna and prairie conditions that were formerly much more abundant and widespread in parts of Wisconsin. Many uncommon plant species usually associated with these habitats were documented in the glades of the Baraboo Hills.
