Cork is a tissue that all woody plants grow to produce bark, which includes non-functional phloem too. Woody plants have a cork cambium, a lateral meristem, that produces an annual layer of cork. You can see the layering of bark in lots of trees. However the stuff we call cork is from the bark of just one species, the cork oak, Quercus suber, a tree that produces a soft, spongy, waxy cork tissue. Every 10 to 12 years or so the bark can be stripped off and made into corks. The problem is that those dark streaks in cork are channels for gas exchange called lenticels that run in and out (you can see them in this chunk of bark). To really seal your wine bottle, the cork must be cut at right angles to the layers of cork meaning the maximum diameter of the cork is limited by the thickness of the cork. That way the lenticels run crosswise in the cork (from the inside out as seen here).But oaks don’t grow very fast, and the demand for cork is greater than the supply, so maybe you’ve seen some of the cheaty composite corks or rubber stoppers or even screw tops (oh, the shame of it) on your wine. Or maybe your wine comes in a box! Now here’s a recycling program you can really support, wine cork recycling, so that the virgin cork can be used for the very important manufacture of wine corks. Some cities and areas have recycling programs coordinated with restaurants because corks really accumulate there, although they pile up quickly around our house. So life is too short to drink cheap wine, and you should recycle those bottles and corks. Drink red or drink white, but drink green.