The science bit
Evergreen tree up to 26m tall. Bark deeply fissured and corky, up to 15cm thick in places. Leaves weakly lobed with a slight point at the tip, up to 4cm long. Each tree has male and female flowers (monoecious). Acorns solitary or paired and are deeply cupped by the upper scales. Pollinated by wind.
- This is one of the few trees able to regenerate their bark. Cork is a kind of bark where the dead cells are waterproofed by a wax called suberin. Most trees produce some cork but the cork oak produces lots!
- One cubic centimetre of cork contains 40 million air cells. It is warm to the touch, durable, light, bouncy, chemically inert, and the suction-cup effect of the cut cells makes it stick to a bottle neck.
- Cork oak wood pastures are rich in plant and animal biodiversity. Buying cork products supports cork oak wood pastures and their biodiversity.
Where it grows
South-western Europe (France, Corsica, Italy, Sardinia, Sicily, Portugal, Spain) and northern Africa (Algeria, Morocco, Tunisia). The cork oak favours acidic soils, requires a hot dry summer season and a cold and moist winter, and can be found in open woodlands, on hills and lower slopes at 300–1000m altitude.
Cork is one of the world's most important renewable forest products. The cork bark is stripped off the tree in a thick cylindrical layer. Each tree is harvested every nine years.
A single tree can cork 4,000 bottles. Fine wines can develop through the happy marriage between cork and a bottle made tall enough to lie on its side. The wine ‘breathes’ through the cork as it ages.
Cork is a biodegradeable alternative to environmentally unfriendly PVC flooring. It is hard-wearing, very sound absorbent and agreeable to walk on due to reflection of warmth and its natural bounce. Cork is also used in insulation, floats, engine gaskets and even skirts, heels and handbags!
Cork oak pastures are under threat as supply is exceeding demand (many wines, for example, now use screw tops), the young are moving away from the farms in Portugal, and climate change is also taking its toll with, for example, desertification in African cork-producing areas.
Cork oaks have been grown since the Middle Ages in Portugal and Spain in open woodlands grazed by sheep and cattle. High-value ham is obtained from the Iberian pigs that thrive on the fallen acorns. No fertilisers, herbicides or irrigation are used. This traditional farming supports a remarkable abundance and variety of rare and endangered wildlife, including the black vulture, booted eagle, Bonelli’s eagle and short-toed eagle, which make giant nests in cork-trees and eats snakes.
- Lobe: incomplete division in any plant organ (eg leaf).
- Scale: overlapping structure on cone or fruit.