Quercus suber

Quercus suber, commonly called the cork oak, is a medium-sized, evergreen oak tree in the section Cerris. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the cores of cricket balls. It is native to southwest Europe and northwest Africa. In the Mediterranean basin the tree is an ancient species with fossil remnants dating back to the Tertiary period.

It endures drought and makes little demands on the soil quality. Cork oak forests are home to a multitude of animal and plant species. Since cork is increasingly being displaced by other materials as a bottle cap, these forests are at risk as part of the cultural landscape and animal species such as the Iberian lynx are threatened with extinction.

The cork oak grows as an evergreen tree, reaching an average height of 10 to 15 meters or in rare cases up to 25 meters and a trunk diameter (DBH) of 50 to 90 centimetres (20 to 35 in). It forms a dense and asymmetrical crown that starts at a height of two to three meters (6 ft 7 in to 9 ft 10 in) and spreads widely in free-standing trees. The crown can be divided into several separate, rounded partial crowns.

The young twigs are densely hairy light gray or whitish. Older branches are strong and knotty. Older trees only form short shoots between 7 to 15 centimetres (2.8 to 5.9 in) in length.

The thick, longitudinally cracked cork layers of the gray-brown trunk bark are characteristic of the cork oak. The cambium of the smooth bark of young trees forms a cork layer very early on, which can be 3 to 5 centimetres (1.2 to 2.0 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. After the cork has been harvested, the trunk appears reddish brown, but later it is significantly darker. The wood is ring-pored, has a brown heartwood and a light reddish sapwood.