Pine trees are not deciduous trees. The leaves of deciduous trees begin to change color in the fall and eventually fall off the tree. Pine trees are called evergreens because they have green leaves, or needles, all year.
Conifers and Evergreens
Conifers, or cone-bearing trees like the pine, are often called evergreens, but not all conifers stay green all year. Not all evergreens are conifers, either.
What Makes Evergreens Green?
What most people refer to as pine needles are actually the leaves of the pine tree. They contain chlorophyll, which gives them their green color.
Protection from the Cold
Pine needles are covered with a waxy coating that protects them from freezing and dehydration. In deciduous trees, cold weather initiates the fall change of colors that leads to leaf drop.
Life of a Pine Needle
Most pine needles do not fall off the tree after a season of growth. They can remain on the tree and stay green for several years.
The chlorophyll in plants and trees absorbs light for the process of photosynthesis, or converting carbon dioxide into oxygen. Pine trees and other evergreens continue to photosynthesize, albeit at a slower rate, during the winter as long as they have enough water.