Wineanorak:

It all starts in the forest. Cork oaks are harvested every nine years, once they reach maturity. It doesn’t harm the tree, and the cork bark regrows. Most cork forests are in Portugal and Spain.

Cork is one of those things you never think about but, when it comes up and you read a story like this, you discover it’s actually kind of fascinating. For example, it never occurred to me that cork was actually tree bark.