Home › Volumes › Trees › How to Know the Trees

The Black Oak Group

The oak form one of the largest and noblest of the tree families. There are 300 species recognised by botanists, and this probably does not include them all. They are distributed widely over the continents of the Northern Hemisphere, and follow the mountains through Central America and across the equator along the Andes. All but a very few species are large trees, important features of the landscape and the commerce of the countries in which they grow. Among broad-leaved trees they hold a preeminent place, and have held it from ancient times, in house and naval architecture and in bridge building. In durability, strength and toughness oak has few superiors.

Fifty species of oak are native to America; half of them distributed in the Eastern and mid-Continental regions, half on the Western slopes. The backbone of the continent, the main chains of the Rocky Mountains, have no indigenous oaks. No Pacific coast species is distributed also in the Eastern States, and vice versa. No European, Asiatic or American species is found outside its own continent, except as it is introduced by man.

The acorn distinguishes oaks from all other trees. It is the characteristic fruit of the family, and is found nowhere outside of it. All oaks bear acorns when they are old enough. Few begin bearing under twenty years of age.

The leaf of an oak is also characteristic. People usually learn to know an oak leaf from those of other trees without realising exactly how or why. There is great variety in the lobing of the leaves, but they are all simple, alternate and almost always oval in outline, leathery, and cut by deep bays, called sinuses.

The flowers of oaks are separate, but near together on the new shoots. The staminate are in fringe-like catkins; the pistillate few-flowered clusters in the axils of leaves; except in the genus Pasania. The acorns are either one or two years in ripening. It happens that annual-fruited species have rounded lobes and sinuses in their leaves. Quercus alba is the type of this class, and as these trees generally have pale bark, they are known as the white oak group. Biennial-fruited species have dark-coloured bark and the lobes of their leaves end in angles tipped with bristly points. They form the black oak group. Their type is Quercus velutina.