The rain and cool temperatures of fall have come to the Pacific Northwest. Thankfully the big leaf maple leaves are turning from a lemony yellow to a rich golden color to help brighten the day. The leaves are tumbling down through the tree canopy creating a blanket on the forest floor. As I walk along, I notice that there is a wide range of sizes of the leaves.
Throughout the canopy of a tree, the leaves can be different sizes. The leaves at the top are called sun leaves. Since they receive more direct sunlight, they are smaller because they don’t need as much surface area to capture light for photosynthesis. The smaller size of sun leaves also serve the purpose of reducing overheating and drying out. Conversely, leaves lower down in the canopy are called shade leaves. They receive light that is dappled, diffuse, or in bursts during brief windows that open during the day depending on the angle of the sun. These leaves grow larger in order to increase the surface area to capture light for photosynthesis. Shade leaves will also grow longer petioles (leaf stems) in order to extend the leaf outwards to capture more light. I can usually find some really long petioles on the big leaf maple on the zig-zag or hillside trails. Kids are good at finding the ones with long stems and running around holding them with their arm extended in the air like they are flying a kite or taking flight themselves in their imagination.
Leaves are an interesting topic and reading about them has inspired me to write future blog posts. I’ll leave it here with the topic of varying sizes on a tree for now. Thanks for reading. I hope to see you out there.
