Cork oak (Quercus suber)
FAGACEAE, Oak Family
Commercial cork is harvested from an evergreen tree called the cork oak, Quercus suber, which is native to the western Mediterranean Region. This particular species produces very thick outer bark composed of cork cells, which have large concentrations of suberin, a wax, impregnating the cell walls.
There is no real substitute for cork, natural or man-made. It is a substance that is water repellent, fire resistant, and indigestible to animals, plus cork does not conduct electricity. You know it from its widespread use for bottle stoppers and floats, but do not forget that cork is also used in many ways to insulate or seal, as gaskets in automobile engines.
The cork oak is grown in orchards especially in southwestern Europe and northwestern Africa, and is an especially famous product of Portugal. This is truly a renewable natural resource. A cylindrical incision is made at the base of the trunk and then up to the first large branch, a lengthwise cut is made, and then the sheet of periderm is pried from the tree in a way that does not damage the vascular cambium. This process does not kill the tree, and years later new periderm has filled in the patch and harvesting can be repeated. The bark must be flattened, because the piece of course was curled (cylindrical).