Nongame and Rare Species Program: Rare Plant Communities of Texas
Edwards Plateau: Central Texas Granite Outcrops
Global Rank: G2
Description: This community occurs on extensive exposures of late-Precambrian granite in the Llano Uplift of central Texas; similar communities are found in the Wichita Mountains in southwestern Oklahoma. The substrate consists of exposed granite surfaces with scattered boulders, crevices, soil-filled depressions, and shallow vernal pools. Vegetation is predominately annual forbs and other species adapted to droughty conditions. Bare rock is occupied by scattered patches of crustose and foliose lichens, mosses, and several ferns and fern allies including Selaginella peruviana, S. arenicola ssp. riddellii, Cheilanthes lindheimeri, C. tomentosa, Woodsia obtusa ssp. occidentalis, and Pellaea wrightiana. Noteworthy plant species in areas of shallow sand or gravel accumulation may include Sedum nuttallianum, Plantago wrightiana, Talinum parviflorum, Helenium amarum, Campanula reverchonii, Aphanostephus skirrhobasis, and Hypericum gentianoides. Areas of deeper soils are usually dominated by Schizachyrium scoparium with other grasses such as Bouteloua hirsuta, B. curtipendula, and Aristida purpurea. Large crevices that contain sufficient soil support woody species characteristic of surrounding woodlands, including Quercus stellata, Q. marilandica, and Carya texana. Narrow or shallow crevices harbor species tolerant of xeric conditions including Echinocereus reichenbachii, Eriogonum tenellum, and Opuntia leptocaulis. Deeper crevices support herbaceous species that prefer moister conditions, such as Tradescantia gigantea, Tinantia anomala, Senecio ampullaceus, the endemic Packera texensis, and Arisaema dracontium. Vernal pools are usually small in extent and may support an unusual flora, including Cyperus surinamensis, Eleocharis geniculata, Fimbristylis autumnalis, Schoenoplectus pungens, and Heteranthera dubia.
Species of Interest: Basin Bellflower (Campanula reverchonii), American Pillwort (Pilularia americana), Bladderwort (Utricularia gibba), Roundleaf Monkeyflower (Mimulus glabratus), Rock Quillwort (Isoetes lithophila), Dwarf Pipewort (Eriocaulon koernickianum), Low Nutsedge (Scleria verticillata)