The bark is rough, though not deeply furrowed and varies from light gray on younger trees to dark or almost black on older ones.
The leaves are of two different types: (1) irregular-shaped lobes, mostly narrow, bristle-tipped, the central lobe often the longest; or (2) pear-shaped with 3 rounded lobes at the outer end. They are dark lustrous green above and gray downy beneath, the contrast being strikingly seen in a wind or rain storm.
The flowers appear in April while the leaves are unfolding. The fruit ripens the second year. The small rounded acorn, about half an inch long, is set in a thin saucer-shaped cup which tapers to a short stem.
The wood is heavy, hard, strong, coarse-grained and is less subject to defects than most other red oaks. It is used for rough lumber and for furniture, chairs, tables, etc. It is a desirable timber tree, especially on the poorer, drier soils. The bark is rich in tannin.
Q. rubra var. pagodaefolia, called swamp Spanish oak, has been collected in four southern counties of Illinois.
BLACK JACK Quercus marilandica Muench.
THE black jack oak is a tree of sandy and clayey barren lands where few other forest trees thrive. It ranges from New York to Florida and westward into Illinois, Arkansas, and Texas. It reaches its largest size in southern Arkansas and eastern Texas. It is found as one of the main species in the “Post Oak Flats” in the southern half of the State and in the sands along the Illinois River, near Havana. The tree sometimes reaches a height of 50 to 60 feet and a diameter of 16 inches, but it is usually much smaller. Its hard, stiff, drooping branches form a dense crown which usually contains many persistent dead twigs. The bark is rough, very dark, often nearly black, and broken into small, hard scales or flakes.