Oak, Post

Post oak, sometimes called iron oak, is a medium-sized tree abundant throughout the Southeastern and South Central United States where it forms pure stands in the prairie transition area. This slow-growing oak typically occupies rocky or sandy ridges and dry woodlands with a variety of soils and is considered drought resistant. In the Southeast, mature post oaks are from 50 to 60 ft tall and from 12 to 24 in in d.b.h. Maximum height rarely exceeds 100 ft, and diameters exceeding 48 in are uncommon. It is one of the most common oaks in the southern part of the eastern prairies, such as in the Cross Timbers.

The LEAVES have a very distinctive shape, with three perpendicular terminal lobes, shaped much like a Maltese Cross. They are leathery, and tomentose, i.e. densely short-hairy, beneath. The angular branching pattern of this tree often gives it a rugged appearance. The ACORNS are one half to 1 inch long, and are mature in their first summer. Acorns germinate in the autumn soon after dropping. They do not exhibit dormancy. Germination is hypogeal. The acorns are sessile or short-stalked, borne solitary, in pairs, or clustered; acorns are oval or ovoid-oblong, broad at the base, 0.5 to 0.75 in long, striate, set in a cup one-third to one-half its length. The cup is bowl-shaped, pale, and often pubescent within. Externally it is hoary-tomentose. The scales of the cup are reddish brown, rounded or acute at the apex, and closely appressed.

Post oak is monoecious; staminate and pistillate FLOWERS are on the same tree in separate catkins or aments. Flowers appear at the same time as the leaves. The calyx is yellow, pubescent, and five-lobed; the lobes are acute and laciniately segmented, with four to six stamens and pubescent anthers. Pistillate catkins are short-stalked or sessile and inconspicuous; the scales of the involucre are broadly ovate and hairy with red, short, enlarged stigmas .

The name refers to the use of the wood of this tree for fence posts. Its wood, like that of the other white oaks, is hard, tough and rot-resistant. Post oak is a valuable contributor to WILDLIFE food and cover. Acorns provide high energy food during fall and winter and are considered important in the diet of wild turkey, white-tailed deer, squirrels, and many other rodents. Leaves are used for nest building by birds, squirrels and raccoons. Cavities provide nests and dens for various birds and mammals. Note: The Post Oak is susceptible to Oak Wilt.