Dendrochronology is a really cool idea - one of the first concepts that I was introduced to when my parents talked to me about science, history, math, conservation, ecology, aging and family history.
I use it too when I talk to people of all ages - it's such a simple and personal thing - to touch the past on the tree stomp! 
So naturally, I try to count the years every time I see a tree stump, I draw one every time I have time for it and one of these days I will get myself a petrified tree with rings - just need to find "the right one". 

And here is a really cool example of how the idea of a tree rings is used to represent data - in this case 200 Years of U.S. Immigration. Check it out - I am part of one of those green dashes.