In the Mediterranean basin the tree is an ancient species with fossil remnants dating back to the Tertiary period.

Since cork for sealing bottles is increasingly being displaced by other materials, these forests are at risk as part of the cultural landscape and as a result animal species such as the Iberian lynx and imperial eagles are threatened with extinction.

[5] The cork oak grows as an evergreen tree, reaching an average height of 10 to 15 metres (33 to 49 feet) or in rare cases up to 25 m and a trunk diameter (DBH) of 50 to 100 centimetres (20 to 39 inches).

It forms a dense and asymmetrical crown that starts at a height of 2–3 m (6+1⁄2–10 ft) and spreads widely in free-standing trees.

The cambium of the smooth bark of young trees forms a cork layer very early on, which can be 3 to 5 cm (1+1⁄4 to 2 in) thick.

The light and spongy cork fabric shows vertical cracks and is white on the outside and red to red-brown on the inside.

[8] The cork oak develops a taproot that reaches a depth of 1 to 2 m (3+1⁄4 to 6+1⁄2 ft) and from which several meters long, horizontally running side roots extend.

At the base of the petiole are two narrow, lanceolate, 5 mm (1⁄4 in) long and bright red stipules that fall off in the first year.

They are bright red at the beginning and stand upright, older catkins are yellow and pendulous, 4 to 7 cm (1+1⁄2 to 2+3⁄4 in) long and have a whitish hairy axis.

[10][12] There are natural populations of the nominate form at altitudes between 150 and 300 m (490 and 980 ft) above sea level, the subspecies occidentalis is found along the Atlantic coast.

[1] Outside of its natural range, the cork oak is cultivated in the Crimea, the Caucasus, India and the Southwestern United States.

Cork oaks have low soil demands and also grow in poor, dry or rocky locations.

They rarely thrive on calcareous soils, but they are often found on crystalline slates, on gneiss, granite and sands.

In addition to these tree species, the shrub-forming species include the Kermes oak (Quercus coccifera), the Lusitanian oak (Quercus lusitanica) the holly buckthorn (Rhamnus alaternus), species of the genus Phillyrea, the myrtle (Myrtus communis), the green heather (Erica scoparia), the common smilax (Smilax aspera) and the Montpellier cistus (Cistus monspeliensis) are often found together with the cork oak.

The bark of the cork oak allows it to survive fires and then simply regrow branches to fill out the canopy.

[17] The most virulent cork oak pathogen may be Diplodia corticola, a sac fungus which causes sap-bleeding sunken canker wounds in the wood, withering of the leaves, and lesions on the acorns.

[17] The common water mould Phytophthora cinnamomi grows in the roots of the tree and has been known to devastate cork oak woodlands.

[17] Several species of butterflies damage the cork oak, the most important being the spongy moth (Lymantria dispar).

The species lays its eggs in the bark of the branches and trunks, and the caterpillars that hatch in spring are distributed in the crown and eat them bare.

The bacterial species Bacillus thuringiensis is used as a biological plant protection agent against the spongy moth.

The lackey moth (Malacosoma neustria) also causes damage to the leaves, sticking its eggs to the bark of thin twigs in multiple rows, and also the brown-tail moth (Euproctis chrysorrhoea), whose caterpillars skeletonize the leaves and further damage the tree after overwintering in spring.

[18] Unfavorable climatic conditions and fungal attack are made responsible for the weakening of trees and for crown damage.

Such fungal parasites of weakness are Botryosphaeria stevensii, Biscogniauxia mediterranea, Endothiella gyrosa and representatives of the mold genus Fusarium.

Cork harvesting takes place every nine to twelve years when a layer thickness of 2.7 to 4 cm (1 to 1+1⁄2 in) is reached.

[23] Cork oaks cannot legally be cut down in Portugal, except for forest management felling of old, unproductive trees, and, even in those cases, farmers need special permission from the Ministry of Agriculture.

The process mandates specialized training due to the skill required to harvest bark without inflicting too much damage to the tree.

[citation needed] Cork oaks are sometimes planted as individual trees, providing a minor income to their owners.

[32] In 2007, a 2 euro commemorative coin with the motif of a cork oak was issued in Portugal in memory of the Portuguese Presidency of the European Union.