Catalog of the woody plants of Oklahoma — descriptions, photos, and range maps for woody plants found in the state.
Flora of Oklahoma Project — information on the flora of Oklahoma with taxonomic keys, and links to additional information.
Oklahoma Native Plant Society — information on the flora of Oklahoma.
Oklahoma Vascular Plants Database — a searchable database of plant specimens from Oklahoma herbaria. Search results yields the number of specimens for a particular species and a distribution map.
Oklahoma wild things — photographs of Oklahoma wildflowers and more.
Robert Bebb Herbarium of the University of Oklahoma — information on the flora of Oklahoma and use of the facilities.
Flora of Oklahoma Committee. 2005. Keys and descriptions of the flora of Oklahoma. Flora of Oklahoma Inc, Noble, Oklahoma.
Stemen, Thomas R. 1929. Spring flora of Oklahoma, with key. Harlow Publishing Company. 241 pp.
Waterfall, Umaldy T. 1952. A catalogue of the flora of Oklahoma; a list of the ferns and flowering plants growing native or naturalized in the state, with references to pertinent literature. Oklahoma State University Research Foundation, Stillwater. 91 pp.
Goodman, George J. 1958. Spring flora of central Oklahoma. University of Oklahoma Duplicating Service, Norman. 126 pp.
Goodman, George J. 1956. Keys to the spring flora of central Oklahoma. Norman, Oklahoma. 54 pp.
Picture Guides and Specialty Books
Little, Elbert L. 1981. Forest trees of Oklahoma. 12th edition. Oklahoma Forestry Division, Oklahoma City.
McCoy, Doyle. 1987. Oklahoma Wildflowers. Published by author, Oklahoma City. 206 pp.
McCoy, Doyle. 1981. Roadside trees and shrubs of Oklahoma. University of Oklahoma Press, Norman. 116 pp.
McCoy, Doyle. 1980. Roadside wild fruits of Oklahoma. University of Oklahoma Press, Norman. 82 pp.
McCoy, Doyle. 1976. Roadside wildflowers of Oklahoma. C & J Printing, Lawton, Oklahoma.