It may be summer now, but we know that soon, the leaves will begin turning their various shades of orange and red until they eventually fall to the ground. As the weather cools, these harsh temperatures and bitter winds would damage the leaves permanently. This is why trees shed their leaves and keep only their strongest, most durable parts to last through the winter: the trunk, stems, bark, and branches.

However, evergreen trees can usually keep their leaves through the winter due to the wax-like substance that their foliage is coated in to protect them from the cold. Their cells actually contain antifreeze chemicals that can help them keep out the bitterness of winter without dying. However, for deciduous trees, the leaves are thin and the tissues are not well-protected. Winter would easily destroy these leaves, so the trees conserve their energy by getting rid of them.

How do the trees know winter is coming?

Trees can actually detect loss of light as the days grow shorter. The chemical receptors in trees called phytochrome (which can detect red light) and cryptochrome (which detects blue) note changes in the length of days, and notice differences starting at just half an hour. When they do feel the days changing in length, they go through both chemical and physical changes that we call “fall.”

What causes the color change?

The heart of the color change we see is chlorophyll, which is the green chemical in plants that allow it to eat. It absorbs sunlight and turns it into food that can be stored for use during the winter, just like hibernation in some mammals. During the summer and spring months, trees produce chlorophyll as quickly as they use it, so the leaves remain green. However, once everything begins to turn colder, this chlorophyll production slows down until it finally stops.

When it stops, the green pigment begins to leave the leaves, leaving behind other chemicals that account for the color. Carotenoids—which produce yellow, orange, and brown colors in other plants (such as daffodils and pumpkins)—are present year round in the leaf, but they only become visible as the chlorophyll leaves the leaf. Similarly, anthocyanins produce red and purple pigments that we see in grapes, plums, and some autumn leaves. The color of an autumn leaf can tell you which pigment a tree has the most of!

How do the leaves fall?

Eventually, it will be time for the leaves to fall. After all, many leaves see a lot of damage throughout the summer, either from bugs, summer thunderstorms, disease, or just general wear and tear. The point where the leaf’s stem meets the branch is called the abscission layer, and this later will choke the veins that give the leaf water and transport the food into the tree. Once it has been completely cut off from the tree, that layer then becomes flaky and weak. It decomposes and then allows the leaf to detach from the tree and fall to the ground below.

However, even though the leaves have fallen from the tree, they are not yet done serving their purpose. As they decompose into the soil below, the earth absorbs their nutrients and uses them to feed future plants that may grow there. Fallen leaves are quite important when it comes to the health of forests and trees as a whole.

What can I do to take care of my trees?

If you want to ensure that your trees stay in the best and healthiest condition, there are a few things you can do. Even in the winter, trees may benefit from a little water every three to four weeks if the temperature is above freezing. Watering them early in the day is a great way to give them enough time to absorb all the water before the temperature drops as the sun sets.

Of course, during the summer months, hiring a professional team of tree care professionals may be just what you need to ensure that your trees remain healthy through both the summer and the winter. At Whatcom Tree Service, we are happy to perform any tree services you may need, including tree trimming, trunk removal, tree removal, pruning, and shaping. Contact our team of experts today to schedule your appointment and let us know how we can help your home!