All oak trees belong to the genus Quercus. There are approximately 600 species of oak the world over, and several subsections, or subspecies, within the genus. From familiar oaks to rare oaks found only in certain areas, there are marked differences between each of these subsections. Learning the basic differentiation between these subsections helps gardeners and nature enthusiasts identify and learn about the varied Quercus genus.
White oaks of the Lepidobalanus subspecies are native to Europe, Asia, North Africa and North America. This subsection includes oaks such as the North American white oak (Quercus alba) and the wooly-leaved oak (Quercus lanata), of the Himalyan mountain range. The subspecies Mesobalanus is native to Europe, Asia and North Africa and includes trees similar to the Italian oak (Quercus frainetto). Subsection Cerris is native to Europe, Asia and North Africa and includes trees such as the Lebanon oak (Quercus libani), of Asia. Subsection Protobalanus includes trees like the island oak (Quercus tomentella), and are native to the southwestern United States and Mexico. The red oaks (subsection Lobatae) are native to North, South and Central America. The red oak subspecies includes the northern red oak (Quercus rubra). The subgenus section Cyclobalanopsis, often called the ring-cup oaks, are found only in eastern and Southeastern Asia. The ring-cupped oak (Quercus glauca) is a part of this subsection.
Lepidobalanus oaks have acorns that take approximately six months to mature. They are edible and taste mildly sweet to mildly bitter. The inside of the acorns of the Lepidobalanus oaks are hairless. Mesobalanus have acorns with similar properties to trees in the Lepidobalanus subsection. Cerris oaks produce acorns that take approximately 18 months to mature. They are extremely bitter tasting and the interior of the shell may be hairless or only slightly hairy. Protobalanus acorns and Lobatae acorns mature in 18 months, taste extremely bitter and have hairs on the interior of the acorn that are woolly in texture. Cyclobalanopsis acorns are marked by cups with rings of scales on the exterior.
Lepidobalanus leaves are rounded. The leaf margins are entire, though they may be deeply lobed. Lepidobalanus leaves do not have bristles on their lobe tips. Mesobalanus leaves form similarly to Lepidobalanus leaves. Cerris leaves have sharp, pointed tips on the ends of their leaf lobes. Bristles are present on most leaves of oaks in the Cerris subsection. The leaves of the Protobalanus are similar to the Cerris-style oak leaves. Cyclobalanopsis oaks have serrated leaf margins, without lobes. The leaves of the Cyclobalanopsis oaks are glaucous, or covered with a greyish-green waxy or powdery substance that is removed from the leaves on contact.