We’re lucky to live in a heavily wooded neighborhood. What grows up sometimes comes down, though, and this was the case for a large Ash tree in our neighbor’s yard. As sad as we are to see a tree cut down, it gave us a fantastic opportunity to see some math in its “natural” habitat.
Have you ever looked closely at the cross-section of a tree? It’s made up of rings, and like our fingerprints, no two trees have exactly the same pattern of rings. Notice the alternating patterns of light and dark wood within the rings. The lighter rings mark the period of the tree’s growth during the spring. During this time, the layers of wood grow fast. The cells in the quickly growing wood are large and airy, which means the rings will appear lighter. The darker rings indicate summer growth, which takes place at a slower rate. The cells in this slower growing wood are smaller and denser, resulting in darker rings.
I always thought you counted all the rings on a tree to determine its age, but the correct method is to count the dark rings. Count the rings to determine the age of your tree, but add 5 to your tally because tree rings begin to show when a tree is about 5 years old.
Now that you’ve figured out how old it was, what year do you think it sprouted? Thinking about the age and size of tree can lead to other questions about how things grow. Can you think of things that grow really fast? What about things which grow slowly? Compared to a tree, do you think humans grow quickly or slowly?
A tree’s rings aren’t perfect or uniform – they can change shape as well as vary in thickness and color. Take some time to examine the rings and let your child point out the different shapes and patterns they see.
By examining the shapes and patterns of a tree’s rings, you can piece together the story of a tree from sapling to today’s mighty log. A few things to keep in mind when examining the tree’s rings:
Did you know you can actually have a job studying tree rings? This particular field of study is called dendrochronology. We haven’t yet interviewed a dendrochronologist for our Bedtime Math So You Wanna Be A … series, but you can read our interview with an arborist who gets to climb a lot of trees.
Kids are used to counting, as well as identifying shapes and patterns in school, but pointing out how these common math concepts occur in nature can be a game-changing experience. In addition to being fun and getting kids outdoors, it shows them that math lives on in the world – not just in books and worksheets. And that’s something we can all wrap our arms and brains around!