12 May 2014

Quercus suber (the Cork oak)

A mature specimen of Quercus suber the Cork Oak tree.

In this photograph it is possible to see several Cork Oaks where the suberin layer has been harvested. 

Here is a close-up of the thick, fissured bark otherwise known as the suberin layer which is stripped every 6 to 12 years leaving the young bark exposed.

The countryside in NW Tunisia is covered with Quercus suber otherwise known as the Cork Oak tree.  There are vast expanses of Cork Oak forest approximately 45,000 hectares in the Jendouba  region and a cork processing factory in the town of Tabarka.

Tunisia is said to export 90% of the cork which is harvested to several European countries.  Cork has many uses such as stoppers in wine and champagne bottles, in shoe manufacturing, as thermal insulation in walls, floors and ceilings and in furniture design to name a few of its uses.

Cork is an impermeable, buoyant material, a prime-subset of bark tissue that is harvested for commercial use primarily from Quercus suber (the Cork Oak), which is endemic to southwest Europe and northwest Africa. Cork is composed of suberin, a hydrophobic substance, and because of its impermeability, buoyancy, elasticity and fire resistance, it is used in a variety of products.

The cork industry is generally regarded as environmentally friendly Cork production is generally considered sustainable due to the fact that the entire cork tree is not harvested; merely its bark. The tree continues to live and grow. The sustainability of production and the easy recycling of cork products and by-products are two of its most distinctive aspects.

The trees live for about 200 years.

Cork is extracted only from early May to late August, when the cork can be separated from the tree without causing permanent damage. When the tree reaches 25–30 years of age and about 24in (60 cm) in circumference, the cork can be removed for the first time. However, this first harvest almost always produces poor quality or "male" cork. Subsequent extractions usually occur at intervals of 9 years, though it can take up to 13 for the cork to reach an acceptable size. If the product is of high quality it is known as "gentle" cork, and, ideally, is used to make stoppers for wine and champagne bottles.

The workers who specialize in removing the cork are known as extractors. Extractors use a very sharp axe to make two types of cuts on the tree: one horizontal cut around the plant, called a crown or necklace, at a height of about 2-3 times the circumference of the tree, and several vertical cuts called rulers or openings. This is the most delicate phase of the work because, even though cutting the cork requires quite a bit of strength, the extractor must not damage the underlying phellogen or the tree will die.

To free the cork from the tree, the extractor pushes the handle of the axe into the rulers. A good extractor needs to use a firm but precise touch in order to free a large amount of cork without damaging the product or tree.

These freed portions of the cork are called planks. The planks usually have to be carried off by hand since cork forests are rarely accessible to vehicles. Finally, the cork is stacked and, traditionally, left to dry, after which it can be loaded onto a truck and shipped to a processor.
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