A FLORISTIC STUDY OF WASHINGTON COUNTY, OKLAHOMA

Washington County is located in northeastern Oklahoma and has an area of 271,713 acres (109,958 hectares). Collections of the angiosperm flora were made during the fall of 1971 and the entire growing seasons of 1972 and 1973. Collecting trips were made throughout the county and as many different localities as possible were visited. In all, 1057 accessions were made and the identified specimens were deposited in the Oklahoma State University Herbarium. This note provides a brief summary of the flora, geomorphology, soils, climate, and plant communities of the county. GEOMORPHOLOGY, SOILS, AND CLIMATE The county is located principally within the Claremore Cuesta Plains geomorphic province. The Eastern Sandstone Cuesta Plains province extends into the western edge of the county at various points. These two provinces contain Pennsylvanian series sandstones and limestones that cap ridges between broad shale plains (3). The ridges have a steep face on the east and a gentle backslope with their height dependent on the thickness of the underlying shale formations. The county is drained by the Caney River, which flows generally south except for an eastward deflection in the central part of the county. Soils are deep to moderately deep and nearly level to gently sloping. Five soil associations are described by Polone (5). Three of the associations, the Dennis-Okemah-Parsons, the Collinsville-Talihina-Bates, and the Summit-Sogn, cover 76 % of the county and support upland prairies. The other two associations support woodlands. The Osage-Verdigris association covers 20 % of the county and supports level bottomland woods while the Darnell-Stephenville association covers 4 % of the county and supports upland woods. The climate is continental with an average yearly rainfall of 90.28 cm (35.55 in). A normal growing season is 209 days with the average last spring freeze on April 2nd and the average first fall freeze on October 28th (6)