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Why do leaves change color in the fall?

Updated: Oct 10, 2023

October is my favorite month. I love the smell of fallen leaves, sweet and spicy. I love the crunch, crunch of leaves as I walk. Every footstep recalls childhood memories of leaf piles and hours of rake, jump, repeat.

Fall is the parallel of spring in that we see rapid changes over the course of the season as Mother Nature closes the books on the growing season. October is the height of these changes as we reach the peak of leaf color.

Colored leaves are the most prominent fall phenophase. But the closer you look the more intriguing beauty you will see: seed pods, ripe fruit, the tans of rustling grasses, drying flower heads. Many thanks to our Backyard Observers who help us document these seasonal changes.

The photos above feather Bur Oak leaves in April and October. Leaves are the food production powerhouses of plants. In the early spring, leaf buds burst revealing miniature-sized leaves that expand and grow many times greater. Day after day, each leaf fuels the plant by producing sugars in a process called photosynthesis, combining water, air and sunlight. As the temperatures cool and days get shorter, photosynthesis slows and the plants prepare for the winter by sending food down to their roots and dropping their leaves.

Sweet Gum (Liquidambar styraciflua), a tree native to Indiana, has intense fall colored leaves that vary from clear yellow to deep reds and maroons. The red and yellow leaves in the photo on the left fell from the same tree. The leaves on the right are from a tree growing in a different location. Spiky gum ball fruits persist on the tree after the leaves fall.

If you love watching the leaves change color, like I do, and also enjoy the other seasonal changes happening around you, consider becoming a Backyard Observer with Indiana Phenology. Tracking phenophases, recording the timing of seasonal changes in plants and animals, can tell us a lot about patterns and trends in climate and how life on Earth is responding to climate change. Our Backyard Observers learn to record phenological observations with an app/website called Nature's Notebook. You get to choose your observation site and the plants you will track. Use your backyard and observe the changing leaves!

We appreciate the dedication of our Backyard Observers and also our supporters who have made a donation to Indiana Phenology. As a small, non-profit, your donation makes a big impact in our work to get Hoosiers involved in the citizen science of phenology in our beautiful Hoosier state! Donate Here

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