Why Do Leaves Fall Off Trees?

When it comes to fall, the first thing many people think of is leaves. The red, golden, and orange-hued foliage that coats trees and eventually falls to the ground is a must-see sight for many. But why exactly does it happen?

As it turns out, trees are pretty smart, and falling leaves are a self-preservative method during the colder months.

Deciduous trees are typically the ones you’ll see lose their leaves during fall. This is because they don’t tend to have waxes and resins to protect them (like other types such as magnolias). During winter, those more fragile leaves would be more susceptible to damage because as water freezes—like it would be likely to do in winter—it expands causing damage to the leaves and making them incapable of photosynthesis. A tree’s got to eat, you know?

Instead of keeping those leaves around, they’re dropped in advance. Plus, shedding those leaves helps ensure the tree’s physical integrity is intact. Snow caught on fragile leaves and windy conditions could bring added weight and stress to branches ultimately causing damage.

How does a tree do this, though? It’s actually a hormonal change that occurs when days shorten and temperatures fall. When those hormones kick in, an abscission process starts and chlorophyll production stops. Here, vessels carrying water and sugar close off, and a new cell layer begins to grow. As it does, the leaves are steadily loosened from the tree and fall.

While yes, those fall leaves are beautiful, they’re also a symbol of the power of nature. The next time you’re planning a leisurely walk or casual drive through the foliage, you’ll now know exactly why leaves fall.