Oak

Encyclopedia article about oak trees

Oak

Common oak (Quercus robur)

Oaks are trees or shrubs in the genus Quercus of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably Lithocarpus (stone oaks), as well as in those of unrelated species such as the African oak (Oldfieldia africana), the Australian oak (Casuarina), and the tanbark oak (Notholithocarpus densiflorus).

Description

A mature oak tree

Oaks have spirally arranged leaves, with lobate margins in many species; some have serrated leaves or entire leaves with smooth margins. Many deciduous species are marcescent, not dropping dead leaves until spring. In spring, a single oak tree produces both male flowers (in the form of catkins) and small female flowers, which can develop into acorns after pollination by wind.

Male flowers (catkins) on a white oak

Acorns

The fruit is a nut called an acorn or oak nut 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 their species. The acorns and leaves contain tannic acid, which helps to guard from fungi and insects.

Distribution

Global distribution of oak species

Oaks are native to the Northern Hemisphere and include deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. North America contains the largest number of oak species, with approximately 90 occurring in the United States, while Mexico has 160 species of which 109 are endemic.

Ecology

Oaks are keystone species in many ecosystems. They provide food and habitat for numerous species of wildlife. The leaves and acorns are a food source for many animals, including birds, squirrels, and deer. Oaks also play a crucial role in forest ecology by providing habitat and food for a wide range of organisms.

Uses

Illustration of Quercus lusitanica

Oaks have been used for thousands of years for their wood, which is prized for its strength and durability. Oak wood is used in furniture, flooring, and construction. The bark of some oak species is used to produce cork, and the acorns have been used as food for both humans and livestock.

Cultural significance

Oaks have been symbols of strength and endurance in many cultures. They are often associated with gods and mythology, such as the Norse god Thor and the Greek god Zeus. Oaks are also national symbols in many countries, including the United States, Germany, and England.

Species

Quercus hispanica

Some notable species of oak include:

• Quercus robur - Common oak
• Quercus alba - White oak
• Quercus ilex - Holm oak
• Quercus suber - Cork oak
• Quercus cerris - Turkey oak

Related pages

• List of Quercus species
• Fagaceae
• Acorn
• Cork oak