The Nutrition Story Behind Fall Foliage
The beautiful reds, oranges, and yellows that flush through our forests in fall actually tell an important story about tree nutrition, and about human nutrition too.
One of the most evocative hallmarks of fall is witnessing leaves change from green to brilliant fiery colors before fading and drifting away. The golds and reds make you think of unpacking your quilt for the first snuggle of the season, of the warm smell of hearty spices, and the way your cheeks catch a brisk morning breeze.
Behind this seasonal phenomenon is actually a fascinating story about nutrition, specifically tree nutrition! Trees are truly remarkable beings, and though you already know they use photosynthesis to create their own energy you might not have thought any further about their nutritional needs. Imagine having only spring and summer to create all the energy you'll need all year. Fall sits at the unique point between a tree's warm weather feast, and its cold weather fast.
Chlorophyll is the green substance in plants that helps them turn sunlight, water, and CO2 into sugar that they use for energy. It's what makes the leaves of happy summer trees bright green. As the days get shorter and colder, deciduous trees (ones that lose their leaves in cold weather) understand that their feasting days are at an end - their leaves are too fragile to survive freezing temperatures and with daylight dwindling they would rather conserve their energy. The first step in this process is packing up the chlorophyll. Rather than allowing green leaves to drop, full of precious nutritional resources, the tree breaks down chlorophyll and begins storing the components in its trunk and roots to save for next year's batch of greenery.
As the green fades, other colors are revealed, unveiling even more about the tree's nutritional story. Trees that turn from green to yellow do so because of a prevalence of carotenoids in their leaves. These are the same antioxidant phytonutrients that give pumpkins, carrots, and bell peppers their golden hues. The carotenoids help the tree absorb light through the spring and summer while also fighting free radicals. Trees that turn from green to red actually are releasing a different kind of antioxidant called anthocyanins, which are also found in foods like pomegranates and raspberries.
While scientists don't fully understand why tree leaves flush with antioxidants as they transition from feast to fast, the prevailing theory is that they do so to protect themselves during a vulnerable time. The tree is extracting all the nutrients it can before its winter slumber, and slowly cutting off each leaf to prevent the infections that could result if the leaf were just torn off to reveal an open wound. The final browning of the leaves comes as it is fully cut off from the tree, begins to break down, and tannins are released.
So the next time you see a tree changing colors, remember how much you two have in common. Both your bodies create and store energy, and take advantage of plant-based antioxidants to protect yourselves from illness and disrepair. Think about how satisfied that tree must be after a successful sunny season of creating the sugars that will nourish it through the winter. And then maybe think about what warm nourishing drink might be waiting for you when you get home!