NBS Blog

Ask a Naturalist: Why do trees lose their leaves in Fall?

Enjoy the first edition of our recurring question-and-answer series, Ask a Naturalist, with questions from the Curiosity Lab's Ask a Naturalist - Answer Tree.

Why do trees lose their leaves in Fall?
– Anonymous

Dearest leaf lover,
You’ve asked an age-old question about Fall-time trees; even the season’s name hints at its annual, leafy phenomenon, queuing the big why for us all!

It’s a wondrous thing at Norman Bird Sanctuary to experience Autumn, both familiar and new, all at once. As summer slips below the horizon, the act of leaves falling somehow feels so … right, and once you get behind the science of it all, you can really appreciate just what Mother Nature is up to exactly!

Imagine the leaf. It needs sunlight and water to source any kind of energy, but as the days grow colder and shorter, it faces slim pickings. Lowering temperatures halt water’s ability to travel from root to leaf without freezing, so the tree goes dormant. You win some, you lose some, right? It’s kind of like trees “win” by losing their leaves and saving their energy.

But my little leafophile, don’t forget that not all trees lose their leaves!

That’s right! Trees that are deciduous, coming from the latin ‘decidere’ or to ‘fall down’, lose their leaves seasonally. Trees that are evergreen stay . . . well, ever green, all year-round!

Now a challenge for you! Head out on the trails at Norman Bird Sanctuary and see if you can spy any trees who still have their leaves! There’s one species I’m thinking of . . . can you guess? Here’s a hint: look for acorns!!

Stay curious,
A Naturalist

This question came from our Curiosity Lab’s Ask a Naturalist: Answer Tree.

You, too, can submit your own question for our Naturalist to ponder!