These soils are derived from glacial materials, sandstones, shales, and limestone and range from heavy clays to loamy sands with some having a high content of rock or chert fragments. The most widespread soils on which black oak grows are the udalfs and udolls. Elsewhere it occurs on warm, moist soils.
In southern New England, black oak grows on cool, moist soils. It is found at elevations up to 1,200 m (3,900 ft) in the southern Appalachians. It grows best in coves and on middle and lower slopes with northerly and easterly aspects. The cap is large and covers almost half of the nut.īlack oak grows on all aspects and slope positions. The fruits or acorns of the black oak are medium-sized and broadly rounded. Black oak acorns are brown when mature and ripen from late August to late October, depending on geographic location.
The fruit, an acorn that occurs singly or in clusters of two to five, is about one-third enclosed in a scaly cup and matures in 2 years. The pistillate flowers are borne in the axils of the current year's leaves and may be solitary or occur in two- to many-flowered spikes. The staminate flowers develop from leaf axils of the previous year and the catkins emerge before or at the same time as the current leaves in April or May. The inner bark of the black oak contains a yellow-orange coloring from the pigment quercitron, which was sold commercially in Europe until the 1940s.īlack oak is monoecious. Some key characteristics for identification include that leaves grown in the sun have very deep u-shaped sinuses and that the buds are velvety and covered in white hairs. There are also stellate hairs on the underside of the leaf that grow in clumps. The upper surface of the leaf is a shiny deep green, the lower is yellowish-brown. The leaves of the black oak are alternately arranged on the twig and are 10–20 cm (4–8 in) long with 5–7 bristle-tipped lobes separated by deep U-shaped notches.
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