|Red or black oak group
The oaks are divided into two broad groups, the red oaks (also referred to as the black oak group) and the white oaks. Cherrybark oak, pin oak, black oak, Spanish oak, shingle oak, northern red oak, and black jack oak are all members of the red oak group. The red (or black) oak group is distinguished from the white oak group by the bristle-tipped lobes on leaves, hairy inner surface of the acorn nut (the nut must be broken to observe this traite), and acorns that require two years to mature. Because they require two years to mature, tiney, first year acorns occur on mature trees along with the larger second year acorns. Acorns of the red oak group are usually bitter and inedible.
The bark of many of the oaks in the red oak group is darker than that of trees in the white oak group.