The black oak, Quercus velutina, is also known as yellow oak, yellowbark oak, and smoothbark oak. It is a common and easily identified tree in the red oak group of oaks. The tree’s scientific name, velutina, is a reference to the velvety texture of fine hairs that are on the tree’s leaf undersides, on the winter buds, and on the leaf stalks (petioles). The common names given the tree refer to the mature tree’s dark gray to nearly black bark, and to the tree’s yellow inner bark which is used to make dye. Found throughout the eastern and central United States, from the Great Lakes to Florida and east Texas, it prefers soils that are moist, rich, deep, well-drained, and acidic. However, it is not tolerant of shade and it is often found in tougher environments where it can get an 
edge on normally faster-growing trees. It adapts to soils that may be dry, average to poor, and neutral to slightly basic. It tolerates grass fires and sprouts vigorously from the root crown when top-killed. The long tap root that helps it survive in extremely dry conditions hinders its use in the nursery trade, so I am confident that the one growing in my back yard was not planted there.
Black oaks are medium- to large-size trees that can grow to 60 to 100 or more feet tall, with slender branches spreading into a narrow, open head. Its spread is often as wide as its height, but sizes and shapes vary with conditions. The tree’s 
trunk may grow to 3 to 4 feet. The tree is anchored by a long tap root that also helps it survive dry conditions. The bark is dark brown and smooth when young, and with age becomes nearly black, thick and scaly with deep furrows. The yellowish orange color of the tree’s inner bark is a feature that helps separate this tree from all other oaks. Leaves are attached to reddish-brown twigs in an alternate pattern, by stout 3 to 5-inch long petioles. These petioles are green spring and summer, and in late summer they turn yellow or scarlet.
Leaves of the black oak may grow to 10 to 12 inches long, often with the end broader than the base. They 
vary very much in shape, and this is an identifying feature of this tree. Those on lower and more shaded branches tend to have lobes that are shallowly incised and may or may not all have points. Higher limbs that get more light have leaves with more deeply incised lobes, with points. There are usually 5 to 9 lobes, and each lobe has teeth that terminate in small bristles. Leaves are thick and leathery, with top surfaces dark green and moderately shiny and undersides dull yellow- or copper-green. The dull appearance of undersides is due to a velvety texture of fine hairs on leaf undersides and petioles, and also on the winter buds. Leaf colors in late autumn range from yellow to 
brick red.
Like all oaks, black oaks have both male flowers (catkins) and female flowers on the same tree. Female flowers are wind-pollinated in mid-spring, and like all trees in the red oak group, they produce acorns that take 2 years to mature. These acorns are light red-brown at maturity, and may be either hemispherical or egg-shaped. They measure 
2/3 to 7/8 inches long, and half or more of their length is enclosed in a thin cap having large, rough scales. These acorn have a sharp point with fine gray hairs on the uncovered end, and also fine gray hairs under the cap. The cap could be either on the narrow end or the broad end of the acorn.
The black oak has many uses. Its wood is considered lower quality than red oak, because it does not prune 
itself as well creating defects, but it is hard and coarse-grained. It is used in construction, for fence posts, railroad ties, barrels, and for fuel. Many also find it useful for cabinetry, furniture, interior trim, flooring, and veneer. Some find it appealing for shade and street use, but long tap roots make this difficult. The U.S. Department of Agriculture says the bark of black oak contains enough tannin to make commercial extraction worthwhile. The inner bark is used to make a yellow dye called quercitron. Native Americans used black oak to treat many ailments including indigestion, chills, fevers, respiratory problems, and sore eyes. They also used it as an antiseptic and to induce vomiting.
A black oak can be readily identified by these features, already mentioned:
-Leaves vary in shape. Those on lower and more shaded branches have lobes that are shallowly incised and may or may not all have points, while those on higher branches that get more light have more deeply incised lobes with points. Red oaks and other oaks with incised leaves have a more consistent leaf shape.
-Leaves have a velvety texture underneath, making them dull yellow- or copper-green. Similarly shaped oak leaves will have little to no hairs on the underside, to have a velvety texture.
-The bark of mature trees is dark gray to almost black, with deep furrows. The most similar oak, the red oak, has a light trunk with silver streaks.
-The inner bark is yellowish orange. No other oak has inner bark this color.
The black oak in my backyard is attractive, casts a good shade, and stands firm to buffer strong winds that could damage my trellis, gazebo, and greenhouse. This common tree can be useful in many ways.