Tree leaves don’t wither or burn, even under the blazing summer sun. In fact, trees provide cool, refreshing shade to people and animals alike with their thick, leafy branches. But what’s the secret behind their ability to stay so green and fresh in such intense heat?
Trees absorb water through their roots and send it upward through tiny tubes called xylem. The water travels through the trunk and branches until it reaches the leaves. Once there, it evaporates through small pores on the underside of the leaves in a process called transpiration. This not only helps pull more water up from the roots, but also cools the tree down by releasing moisture and heat into the air. That’s why it feels so cool under a tree—the evaporating water is actually lowering the surrounding temperature.
The hotter and sunnier it is, the more active this process becomes. A large tree can release around 200 liters (over 50 gallons) of water in just one hour during a summer afternoon.
Because the leaves are constantly pulling in moisture to release it, they stay full of water and never get a chance to wilt. Trees don’t avoid the heat or shrink away from it; they stand tall and beat it in their own steady way.