The cork tree, formally known as Quercus suber, is a species of evergreen oak recognizable by its unique, thick outer covering. This distinctive tree is native to the western Mediterranean basin, thriving in countries like Portugal, Spain, and Morocco. The primary reason for its cultivation is its remarkable bark, which is the sole source of commercial cork. This resilient species is long-lived, often surviving for 200 years or more, and supports a diverse ecosystem in the open woodlands where it grows.
The Distinctive Cork Bark
The bark is the defining visual trait, appearing light gray to ashy-white and growing up to 12 inches thick on mature trees. The surface is rough, deeply furrowed, and spongy to the touch, giving the trunk a gnarled and ancient look. This thick layer of cork is an adaptation that allows the tree to survive frequent forest fires common in its native habitat.
The appearance of the trunk changes drastically after the cork is harvested, which occurs every 9 to 12 years after the tree reaches about 25 years old. Specialized workers strip the outer layer, revealing the smooth, newly exposed inner layer. This uncovered trunk is a striking reddish-brown or fiery orange color, which gradually darkens as it is exposed to the elements.
The color contrast between the newly stripped, smooth area and the remaining rough, gray bark is a reliable way to identify a recently worked cork tree. The first bark removed, known as “virgin cork,” is cracked and irregular, while subsequent harvests yield a more uniform and softer material. The tree regenerates its outer bark, a process often marked on the trunk with painted numbers indicating the year of the last harvest.
Overall Size and Canopy Structure
The cork oak is a medium to large tree, typically reaching heights between 30 and 60 feet when mature, though some specimens reach up to 70 feet. The tree develops a short, stout trunk that often appears twisted or gnarled, especially in older individuals.
The canopy is broad, dense, and rounded or irregularly shaped, often spreading as wide as the tree is tall. When grown in commercial plantations, trees are pruned to encourage a lower, wider crown and thicker branches to maximize bark production. This cultivation technique results in a picturesque, open-branched silhouette, well-adapted to the open, often windy landscapes of the Mediterranean.
Identifying Leaves and Acorns
The foliage of Quercus suber is evergreen, contributing to its dense, dark appearance. The leaves are small, measuring between 1 and 4 inches long, with a leathery texture. The upper surface is a shiny, dark green, while the underside is often covered with a dense layer of grayish-white hairs, creating a two-toned effect.
The shape of the leaves varies, ranging from oval to ovate, and they feature wavy or sparsely toothed margins. These edges sometimes have a spiny appearance, resembling the leaves of holly. The fruit of the cork tree is an acorn, which is elongated and narrow, measuring about 1 to 1.5 inches in length. The nut is partially enclosed by a shaggy or scaly cap, which covers about one-third to one-half of the acorn.