While autumn can be defined in many ways, for many, the true mark of the fall season is the changing of the colour of tree leaves from green to gold, red, and orange. However, some trees, namely evergreens, stay green all year round. To better understand why these trees keep their green appearance, we’ll look at the science behind why leaves change colour and why it doesn’t affect evergreens. We’ll also examine whether these differences mean evergreen trees don’t require as much care as their colour-changing counterparts.
Why Do Some Trees Change Colours in Fall?
When you think of summer-time deciduous trees, you likely picture their solidly green leaves. These leaves are green because they are filled with chemicals that are also green. The most common of these chemicals is chlorophyll, which plays a key role in turning sunlight into nutrients through a process called photosynthesis.
As temperatures begin to dip, however, sunlight becomes less apparent, and periods of daylight grow shorter. Deciduous trees notice this, and, to prepare themselves for the oncoming winter and lack of opportunities for photosynthesis, they begin to reduce their production of chlorophyll to zero. Without chlorophyll, the leaves lose their green and turn red, yellow, or orange.
Why Do Evergreens Stay Green?
While winter can affect the metabolism of coniferous trees (i.e., evergreens) just as affects that of deciduous trees, evergreens operate differently when it comes to their growing and maturation cycles. Deciduous trees have leaves with only one growing season, so they must turn off their production of chlorophyll, so it’s not wasted on leaves that die every winter.
Instead of leaves, evergreens have needles that have multiple growing seasons each year. This allows the tree to hold onto their needles longer and continue to provide them with chlorophyll and keep them green all year long. These multiple growing seasons throughout the year also help evergreens grow in climates and environments in which normal leaf-bearing trees would struggle, such as at high altitudes and latitudes.
Do I Still Need To Care for Evergreens?
Evergreens are remarkably hardy trees, but that doesn’t mean their needs should be ignored or that they don’t pose a hazard during periods of heavy snowfall. Evergreens grow in a way that allows snow to fall off them during times of accumulation. However, heavy snow loads can still break branches, causing potential damage to property or people.
Evergreens are also susceptible to extreme cold. Subzero temperatures can cause something called “cellular freezing,” which can kill the tree. Evergreens do have built-in biological systems that can help lower the freezing point of water in their cells, but lowering the freezing point isn’t the same thing as eliminating it. This means that even with these protections, evergreens are still vulnerable to harsh winter environments.
How Can I Protect My Evergreens?
One of the best ways to protect your evergreens during winter is to continue watering them into the fall and until the soil begins to freeze. Evergreens will be able to store the water even as they lose the ability to absorb water through the frozen soil.
You can also build a screen or shelter to help shield your evergreens from fierce winds, snow accumulation, and damage caused by road salt. You should use fabric, such as burlap, which is somewhat porous so the tree can continue to breathe. Avoid plastic coverings as that will result in hot temperatures, which can also damage the tree.
If you need help making sure your evergreens stay evergreen, you should also consult with a professional tree service, such as Martin’s Tree Service. We offer a variety of services that can help protect your yard’s deciduous and coniferous trees.