Oak

Oak is a common name for many species in the genus Quercus of the beech family, Fagaceae. This group includes trees and shrubs in the Northern Hemisphere, from cool temperate to tropical latitudes and also in high altitude tropical regions.

Description

Oaks have spirally arranged leaves, with a lobed margin in many species; some have serrated leaves or entire leaves with a smooth margin. The flowers are catkins, produced in spring. The fruit is a nut called an acorn, borne in a cup-like structure known as a cupule; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on the species.

Classification

The genus Quercus is native to the Northern Hemisphere and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in Asia and the Americas. North America contains the largest number of oak species, with approximately 90 occurring in the United States.

Uses

Oak wood has a density of about 0.75 g/cm3, great strength and hardness, and is very resistant to insect and fungal attack because of its high tannin content. It also has very appealing grain markings, particularly when quartersawn. Oak planking was common on high status Viking longships in the 9th and 10th centuries.

Ecology

Oaks are used as food plants by the larvae of Lepidoptera (butterfly and moth) species. Oaks are also the habitat of many species of birds and mammals.

Cultural significance

The oak tree is a symbol of strength and endurance and has been chosen as the national tree of many countries including England, France and Germany.