Why Do Tree Leaves Change Colors in the Fall?

Thanks to the incredible colors that appear, Fall is one of the most beautiful times of year in many places. Instead of the pretty, yet monotonous green tones that have painted the landscape for the last 6 months, the trees become clad in gold, red, orange and purple hues.

Because the green color of leaves is a crucial factor in the biology of trees, many people are curious why tree leaves change color at this time of year. But, rather than having a reason for doing so, this phenomenon actually represents a beautiful byproduct of the dying process.

Why Are Tree Leaves Green in the First Place?

Like all other advanced plants, trees make their own food through the process of photosynthesis. This process works by converting the water and carbon dioxide the trees collect into sugars, which serve as the plant’s food. Green plants rely on a substance called chlorophyll to capture the energy in sunlight and use it to drive the chemistry behind photosynthesis.

Chlorophyll – which is found throughout leaves and a few other plant tissues – is green. This, in turn, means that the leaves of plants and trees are usually green.

Why Do Tree Leaves Change Colors in the Fall?

As the nights grow longer and the days shorter, some trees begin preparing for the coming Winter. Because leaves help the tree draw water from the ground and then release it from small holes on the leaf surface, many trees shed their leaves during this cold, and often dry, portion of the year. This helps them to avoid becoming stressed by a lack of water.

As part of this process, the chlorophyll in the leaf begins to break down. When this happens, other pigments that are already present in the leaf become visible. Two such pigments are especially important in this context: carotenoids, which produce yellow and orange colors, and anthocyanins, which produce red tones.

Because different species and individuals have different amounts of these pigments inside their leaves, their leaf color can vary. This is why one sugar maple on your street may turn bright red, while another turns a rich gold color.

What Types of Factors Influence Fall Color in a Given Year?

You may have noticed that not all Falls are created equally, and the leaf color in some years is much more vibrant than in others. There are a few reasons for this year-to-year variation, but most relate to the weather during the previous spring and summer.

Typically, the best fall color follows years with ample growing-season rain and dry, warm and sunny weather during the late summer and early fall. The first factor ensures that the tree will produce lots of healthy foliage, which will remain intact and healthy late in the season, thanks to the lack of rain.

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Fall color is a little tamer in California than it is in many east-coast cities, but there are a handful of high-color trees that thrive in our region’s Mediterranean climate. If you’d like to add a little red, yellow and maroon to your yard next Autumn, call your friends at Evergreen Arborist Consultants. One of our trained arborists will visit your property and recommend a few species that are likely to thrive there. We can even help with the installation process if you’d like.