Why Do Trees Lose Their Leaves: A Tree Owner’s Guide

Why do trees lose their leaves? Changing seasons bring a riotous display of color before the cold winter causes leaf drop. So why do deciduous tree leaves go through this process every year? 

In this post, New Leaf Tree Service, your trusted tree service in Louisville, KY, answer the question, “Why do trees lose their leaves?” in greater detail. 

Why Do Leaves Change Colors Before Falling?

The color of a leaf depends on the chemical processes within that leaf. Most leaves are green due to the chlorophyll that helps them turn sunlight into energy. Green is the best color for this process, so leaves are green during the sunniest months to maximize energy production and growth.

As fall approaches, the leaves have plenty of stored energy on which to draw during winter. They now start to slow down and stop producing chlorophyll. This reduction makes the carotenes in the leaves more obvious. 

While the carotenes were there all along, the chlorophyll overwhelmed them, making them practically invisible. In the fall, the plant begins to produce anthocyanins instead, and these chemicals allow the carotene to shine. We get wonderful yellows, pinks, and reds coming to the fore. 

Depending on the conditions, the trees may produce higher levels of anthocyanins. If fall is sunny and dry, the leaves take on a fiery red tone. However, the process is slow and not uniform, so we see a bright mix of leaf colors on the trees. 

If you were wondering, “Why do trees lose their leaves?” this is the most interesting part. 

As the leaves begin to die off, they turn brown and wither and fall off. This is a process that accelerates in late fall due to cooling winter temperatures. 

In spring, the abscission layer prepares the tree for sunny weather by sprouting leaves from the branches. The abscision layer is a selection of cells responsible for transporting energy from the branch to the leaves. A hormone known as auxin stimulates this process.

As the weather begins to cool and the days shorten, the tree produces less auxin. This weakens the abscission layer, making it harder to maintain a strong bond between the branch and the leaf. As time passes, the wind blows more leaves away, leaving the tree bare. 

Why Does the Tree Need to Lose Leaves? 

Trees lose their brown leaves for several reasons, including:

  • To conserve energy throughout the winter when rain and sunlight are more scarce.
  • To save the water, especially in colder climes where groundwater may freeze.  
  • To make it easier for trees to deal with the impact of harsh winter storms. They offer less resistance without leaves. 

Why Do Some Trees Keep Their Leaves?

Evergreens, like conifers, have a very different structure. They have needles instead of leaves and resinous sap. The needles can better withstand temperature extremes because they are stronger. 

Conifers are also more streamlined in that they have pointed crowns rather than outspread canopies. Their shape makes it easier for snow to slide off. Finally, many of these trees can handle freezing until their cells recover during the spring thaw. 

In short, evergreens have a natural ability to withstand colder weather, so they don’t have to lose their leaves.

Contact the Experts

Why do trees lose their leaves in summer in Louisville, KY? That is a more difficult question to answer and may be due to many issues like malnutrition or illness. You can learn how to tell if the tree is sick by contacting our team at New Leaf Tree Service at (502) 419-9899 to schedule service.

Are trees on your property dying, falling down, or causing you concern? We are ready to hear from you! If you have dying trees, ugly stumps, or just need your landscape cleaned up from fallen debris, reach out today.

Contact Us

4124 Bishop Ln 103
Louisville , Ky 40218

(502) 419-9899