Dendrochronology is a way to mark time when you run out of fingers. Everyone knows that a tree puts on a new ring each year so when you cut one down, or more politically correct these days, take a core, you come to understand the wealth of information embedded in the rings of a tree. A recent article in Wildflower, the print and digital magazine of the Lady Bird Johnson Wildflower Center (Austin, Texas) is the perfect place to go to learn more.