How do evergreens stay green?

Have you ever stopped to wonder how evergreen trees manage to keep their needles and stay green while so many others do not? Take a walk outdoors this time of year and you will certainly notice an abundance of leafless, dormant trees. However, you will also notice the plentiful green needles or evergreen trees.

Most of the evergreen plants on the installation are conifers. Conifers, such as pines and fir trees, are plants which bear cones and often have needle-like leaves. These conifers are an ancient group, whose ancestors date back to about 300 million years ago.

But, why do these plants stay green all winter? Conifers, just like all other plants, use photosynthesis to survive. Photosynthesis is the process by which plants use a pigment called chlorophyll to harvest the energy from the sun to make sugars. Chlorophyll is green and, therefore, plants that have the ability to undergo photosynthesis are green, as well. The evergreen plants you see during the winter retain the ability to make energy for themselves.

However, during much of the winter, the temperature is too cold and there is not enough water to allow photosynthesis. During these times, evergreen trees are dormant. In the balance between keeping your leaves while not using them, or losing your leaves and thus needing to grow new ones every year, evergreens have "chosen" to keep them. They are then able to produce energy during times when water is available and the temperatures are mild.

With so many plants and animals dormant or out of sight during the winter, you may have a better chance to notice the life that continues to persevere. So, next time you see
something interesting in nature be sure to ask "how is it doing that?"