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Losing leaves

Most plants lose their leaves in the fall when it turns colder. This strategy protects the rest of the plant. Plants usually lose their leaves when conditions in the environment, such as drought or cold, become too harsh for the plant.

Plants lose a lot of water through their leaves. The leaves basically sweat, losing water into the air. In drought conditions, losing the leaves helps the tree keep water in other parts of the plant. The tree doesn’t dry out as much.

Other plants have leaves that can’t handle the cold. When the first frost comes, leaves die and drop off. The plants suck back all the sugars and other nutrients, or food, that the leaves were using. Plants store these nutrients through the winter until they need the stored food to grow new leaves in the spring.

A different way

Evergreens have adapted a different way of surviving. They keep their leaves on. As the weather turns colder, chemicals, or substances, in evergreens begin to change.

Special parts of their leaves change fats, proteins and sugars into a kind of antifreeze. This antifreeze substance allows the leaves to stay on the tree during the cold winter.

Changing with the times

Evergreen trees change their chemistry in other ways too. The whole plant, right down to the fragile twigs, becomes hardier in the cold.

Evergreens that grow high in the mountains may need even more protection. These mountain trees build up even more antifreeze chemicals in their leaves. They don’t grow tall. That way, they limit their exposure to the wind and cold.

Evergreens can grow in high altitudes. They are often the only trees able to grow high in the mountains. This skier is enjoying the view from Olympic National Park in Washington.