Georis Winery in Carmel Valley has a beautiful cork tree in their tasting area. Seeing such an interesting tree makes you wonder how often cork is harvested. It also comes up from time to time when tasting. I had it in my mind that it could only be harvested every 70 years, which, when said aloud, sounds like it can't possibly be true. I took out Jancis Robinson's, The Oxford Companion to Wine to get my facts straight.
Cork trees are a species of oak
First harvest - 25 years
Subsequent harvests - minimum 9 years (according to Portuguese law)
Average lifespan - 170 years