Why Do Leaves Change Color in the Fall?

Everyone takes pleasure in seeing the picturesque colors of autumn leaves, but why do leaves change color in the fall? Many people may have wondered why and how they change? Why do maple leaves turn red? How do shades of orange and yellow emerge?

To know the answer to the question, why do leaves change color in the fall, you must first understand what leaves are and how they function. For example, it is important to understand that every leaf growing in a tree branch is like a miniature factory that works 24/7 to produce its food, or energy. It is also important to know where leaf color comes from in the first place.

Where Does the Leaf's Color Come From?

The leaf's color comes from the three natural pigments that are present in the plant’s cells structures.

• Chlorophyll is one of the three pigments that is responsible for giving leaves their green color. This is the leaves’ most important pigment since it aids in its food production wherever and whenever sunlight is present.
• Carotenoid is another pigment found in leaves. This pigment gives leaves their orange, yellow, and brown colors. This pigment is also found in many fruits and vegetables such as carrots, corn, and bananas.
• The third pigment, anthocyanin, gives leaves their red color. It is also found in fruits such as apples, cherries, strawberries, and cranberries.

Changing Colors

In the summer months, the chlorophyll in leaves covers the other pigments and therefore gives leaves its dominant green color during the summer.

During the fall, the length of the day decreases and temperature changes occur. As mentioned, chlorophyll can only be produced when sunlight is present. During the fall, less chlorophyll is produced since the days are shorter. The rate of chlorophyll production decreases, therefore the color green in leaves fades off.

Leaf Pigmentation

Carotenoids are more stable than chlorophyll and will not decompose as easily. Furthermore, unlike chlorophyll, the production of carotenoid is not light dependent. Thus, carotenoid molecules will increase while the chlorophyll pigments decrease. This leads to the orange, yellow, or red colors in leaves during autumn. Leaves containing anthocyanin will also change color as chlorophyll decreases. Red may turn into purples due to high levels of anthocyanin.

How Leaves Get Their Fall Colors

Part of knowing why do leaves change color in the fall involves knowing how they get their specific colors. If anthocyanin and carotenoids are both present in leaves, they will turn orange. If both are not present, other compounds found in the leaf such as tannins, will give leaves their brown color. For instance, leaves of oak tress turn brown.

Temperature 

Temperature also affects the changing of leaf color. During the warmer days, leaf colors are brighter since anthocyanin will require the presence of sunlight. If the sky is overcast with dull light, leaves will take a shade of yellow or brown.

Warm and sunny days plus cool and crisp (not freezing) nights bring the most beautiful medley of colors. During this season, leaves produce lots of sugar but due to the cooler nights and the closing of leaf veins, sugars cannot move out. These conditions (high sugar content plus light-spurs) will produce vibrant anthocyanin pigments –tints of purple, crimson, and red. Since carotenoids are always present in plant leaves, gold and yellow colors are constant every autumn season.

Moisture Content

Moisture content in the soil will also affect leaf colors. Just like the weather, the moisture in the soil will vary from season to season. The combination of these variable factors makes it possible for having no two fall seasons exactly alike.

Late spring or a summer drought can cause a delay in the autumn color change, while a warm fall will also lower the vibrancy of the fall colors. A warm, wet spring with sunny autumn days plus cooler nights will produce more intense and brilliant autumn colors.  

Dying Leaves

Red and yellow pigments will soon start to disintegrate and decompose once the leaf falls to the ground. Dead leaves are brown in color. You will notice a vast carpet of brown, dried leaves on the ground toward the late part of fall.

Fall is such a beautiful season with its display of bright and warm colors, its no wonder why this a favorite season of many. It’s very easy to enjoy this charming season especially with a cold nip in the air. It’s the perfect time to enjoy Mother Nature's creations and witness how nature likes to play with brilliant colors.