A Tree in Winter

by Roy Winkelman

This is a photo of a tree in winter in Western Pennsylvania. Depending on the age level and background knowledge of your students, this photo can be a springboard into understanding something that at first seems pretty mysterious. How does a tree survive a cold winter?

Some animals migrate to warmer climates when it gets cold. Others hibernate. Some animals are warm-blooded and have thick fur coats to protect them from the cold. But trees?

Here are some questions that will lead your students in an investigation of how trees survive winter.

• Plants are made up of a large percentage of water. Water usually freezes at 32˚F (0˚C). Where this tree is located, the temperature sometimes drops below 0˚F in winter. Why doesn’t the water in the tree cells freeze and kill the tree?
• What does losing leaves have to do with preparing for winter?
• How can trees with needles survive cold when broadleaf trees must shed their leaves?
• A fur coat of dead cells helps to keep mammals warm in winter. What sort of coat does a tree have?
• Do trees expend much energy on growth in the winter?
• How do trees protect cells from having ice crystals form WITHIN the cells where they would cause damage?