Ohio is part of the great central-hardwood-forest region. Geographically, it lies near the north-central portion of this extensive region that extends northward to Michigan and Wisconsin, eastward to the Atlantic coast, southward to the pine areas of Georgia, Arkansas, and Texas, and westward to the Great Plains and prairie states. A great many trees representative of other forest regions extend into Ohio. For example, in northeastern Ohio the white pine, hemlock, yellow birch, beech, and sugar maple grow native. These trees are typical of northern forest areas. In southeastern Ohio the shortleaf, pitch, and scrub pines are more typical of the southern forest regions. Hardwoods of the southern forest region include the blackjack oak, Spanish oak, sourwood, and bigleaf magnolia that have advanced into the state from the lower Allegheny and Appalachian areas. In southeastern Ohio many trees are limited in their distribution and are entirely confined to southern Ohio.
The state forest park areas of Hocking and Fairfield counties contain many examples of the overlapping and blending of northern and southern species. The hemlock, Canadian yew, and black birch are found as remnants of a northern-type forest surrounded by a southern-climate forest of the oak, hickory, chestnut-type, associated with rare species from the south such as umbrella magnolia, shortleaf pine, rhododendron, sourwood, fringetree, and aralia, or Hercules' club.
The greater portion of Ohio's land area was once covered with a dense, virgin forest. Of the almost 26.1 million acres of land, approximately 25 million acres were covered with forests. By 1940, this huge forest had been reduced to about 1.6 million acres, or about 10 percent of the total land area. Clearing for agricultural purposes was the principal reason for the clearings. Over the last 50 years, Ohio has added to its woodlands. By 1996, Ohio had 7.9 million forested acres and was 30 percent wooded.
Breaks in the original forest area existed in the western sections of the state where prairie openings or patches existed and in the wetlands along the Lake Erie shore. Prairie openings were typical of Indiana, Illinois, and Iowa and were dominated by tall prairie grasses. Associated with these openings or patches were scattered trees of open-forest growth, characterized by a bur oak-hickory type that is commonly distributed in Madison, Champaign, Fayette, Greene, and Clark counties today. There were, however, no extensive areas comparable to the vast prairie openings of the middle western states.
The forests of Ohio contain a wealth of native tree species. At least 120 species of trees are native to the state, not including the small trees such as hawthorns that would add approximately 30 more species or varieties to the list. Of the 120 species of native trees, 14 species belong to the oaks, six to the hickories, six to the ash, and seven to the maple group. In addition, 15 species of willow have been identified in the state, although only three are of commercial importance.
Southeastern Ohio probably has the greatest number and type of native trees. In a forest survey made by the Ohio Department of Natural Resources, Division of Forestry, a complete checklist was made of all native trees in 10 southeastern counties. A total of 87 species of native forest trees were found growing in the 10-county area. Of the 87 species, 13 were oaks, including two extremely rare oaks to Ohio. The blackjack oak and the Spanish oak also were discovered. Of the total number of trees growing in the surveyed areas, 45 of the 87 species were of commercial importance for saw logs, lumber, pulpwood, and post purposes.