Why Do Leaves Change Color in the Fall? Leaves in Autumn, Fall Foliage Pics

Why do leaves change color in the fall? Leaves change color in the fall because the amounts of pigments change as the leaves in deciduous tree prepare to drop (no longer needed) in the winter.

There are many reasons to love fall including the (sometimes brisk) milder weather, less crowded parks and trails, and of course, squash, and pumpkins. But the best is certainly the change of colors in the leaves.

But why exactly does this happen? And which trees offer the most glorious and striking fall shades?

And… are there certain conditions that increase or decrease the amount of color saturation?

This complete guide explains the answer to the question, why do leaves change color in the fall, and provides a number of different types of trees with leaves in autumn changing colors.

Plus, it includes some lovely fall color images that will help you anticipate the coming season.

When Is Fall? Why Do Leaves Change Color in the Fall?

Before getting into fall, let’s understand the seasons of the year.⁶ A year has four seasons.

The four seasons, spring, summer, fall, and winter, follow each other regularly. Simply put, a season is a time of the year differentiated by climate conditions.

Seasons happen because of factors related to Earth’s tilted axis as it rotates around the sun. The spinning is because the sun attracts and pulls the Earth towards it.

Throughout the year, different parts of the Earth get the sun at different intervals. So, when the North Pole directly faces the sun, it’s summer in the Northern Hemisphere and winter in the Southern Hemisphere, and vice versa.

So, when is fall? Autumn or fall in the Northern Hemisphere is the period between the autumnal equinox (day and night are equal in length), September 22 or 23, and the winter solstice (the shortest day), December 21 or 22.

The Southern Hemisphere is between March 20 or 21 and June 21 or 22.

Fall Foliage: The Science Behind Fall Leaves Color

If there’s something fall is known for: it’s the change of color by leaves.

Unfortunately, this stunning phenomenon doesn’t happen everywhere in the world.

So if you live in an area that experiences the fall leaves color change, it’s best to go out and enjoy this nature’s gift. But why do leaves change color in the fall?

This article tackles this question. But first, why are leaves green?

Why Do Most Leaves Appear Green?

Leaves get color because of chemicals called pigments.⁵

There are three main types of pigment in each leaf:

• Chlorophyll (greens)
• Carotenoids (yellow and oranges)
• Anthocyanins (reds)

Leaves are usually green because of the presence of chlorophyll. But carotenoids are also present but are overshadowed by chlorophyll.

Chlorophyll helps plants absorb sun energy as they undergo photosynthesis. The leaves are triggered to keep making more chlorophyll because of a lot of sunlight during the summer and spring.

What Cause Leaves To Change Colors?

The plants continuously produce chlorophyll during the growing period (summer and spring). But as fall draws near, the days become shorter, nights become longer, and there is less sunlight—this signals the leaf to prepare for winter.

Chlorophyll production slows down and eventually stops. When this happens, the leaves start to lose their green color.

The orange and yellow colors become visible (yellow and orange pigments are usually already in the leaves but masked during the warm months).

Red leaves happen because of anthocyanins. This pigment is not part of the leaf in the growing season.

So, how does it occur? When the fall days are warm enough for the food factories to function, but the nights are too cold for the sugar produced to move down the plant, the sugars get trapped in the leaves.

They produce anthocyanins. Brighter light increases the production of anthocyanins, and the plant gets brilliant red leaves.

Why Do Leaves Change Color in the Fall? Factors That Contribute to Color Change in Leaves in Autumn

Why do leaves change color in the fall?

Certain factors influence the pigments that appear in leaves during the fall.

The beautiful colors of autumn display are caused by these three factors, leaf pigments, length of night, and weather.

Leaf Pigments

As discussed above, there are three main types of leaf pigments:

1. Carotenoids: Carotenoids are tetraterpene pigments. They are responsible for the display of yellow and orange colors of leaves.
   They are usually the most distributed pigments. Carotenoids are present in photosynthetic bacteria, some species of fungi, algae, animals, and plants. They are responsible for tomatoes, oranges, carrots, and beetroot colors. Carotenoids are always present in the leaf during summer and spring.
   However, it’s hidden due to the large production of chlorophyll.
2. Anthocyanin: When sunlight starts to disappear for more hours each day, the veins that transport fluids within the leaf begin to clog. As a result, sugar is trapped within the leaf.
   As the concentration of sugar in the leaf increases, the production of anthocyanins is triggered. The pigments make the already yellowing leaves turn red.¹ This pigment is responsible for the stunning display of the Red Oak Tree, Red Maple Tree, and Purple Ash Tree​ during autumn and the normal color of red apples, cranberries, strawberries, blueberries, cherries, and plums.
3. Chlorophyll: As discussed above, this pigment gives leaves a green color. It enables plants to use sunlight to make energy through photosynthesis.⁴
   The decline in production of this pigment allows the other pigments to show.

Night Length

Summer and spring are characterized by long, warmer days. This is the plants’ growing season, and much chlorophyll is made, enabling the plants to stay green.

However, during fall, the days become shorter, nights longer, and light intensity decreases. Production of chlorophyll slows down and then stops.

Weather

When, how long, and the intensity of fall colors depends on the weather.² This ensures there are no two falls that are the same.

Moisture and temperature are the main influences. The best color display comes along when there are warm, sunny days but cooler nights.

This enables the production of lots of sugar during the day, but the cool nights and vein closure prevent the sugar from moving out. Anthocyanin pigments are then produced.

If the warmer days and cooler nights continue, more anthocyanin is made, and the colors pop more. Extreme weather changes can also affect the leaves.

Drought during summer or spring will affect the soil moisture content, resulting in the leaves falling early. An early frost has the same effect as the leaves could drop before changing colors.

Yellow Falling Leaves: Why Do Trees Lose Their Leaves?

There are three basic types of leaves on trees: needles, scales, and broadleaf. Most types of evergreen trees have scales or needles, and most broadleaf trees are deciduous.

Changing color and dropping of leaves is associated with deciduous trees and not evergreen. There are many reasons why deciduous trees change color and drop their leaves during fall or autumn.

First, it’s a means of self-protection.

During winter, it gets super cold and dry. The leaves don’t get nutrients and water to function normally.

For this reason, they drop the leaves to conserve water and energy. The moisture is preserved within the trunk, preventing the root from drying out.

Secondly, the shedding of leaves allows harsh wind to blow through the branches. This puts less strain on the tree.

Examples of deciduous trees include:

• Dogwood Tree
• Cherry Tree
• Hickory Tree
• Beech Tree
• Aspen Tree

But why don’t evergreen trees drop their leaves?³ Evergreens also drop their leaves (needles) but not all at once, so you might not notice.

Evergreen trees have thick waxes and resins, allowing them to conserve water during summer and spring.

Because of this, their leaves stay green and remain attached longer. So, how many leaves are on a tree?

On average, a mature tree can have about 200,000 leaves. The leaves shed and grow back throughout the tree’s life.

Why Do Leaves Change Color in the Fall? The Mix of Green and Yellow/Red Leaves on Trees in the Fall

As mentioned above, the leaves change color when they stop making chlorophyll, resulting from longer nights in autumn. But why do some trees have a mix of green and yellow leaves?

A lot is still yet to be known about the autumn leaves colors.

However, the mixed colors result from micro-environmental factors, like only part of the tree is exposed to sunlight or cold. As we move further into fall and all the leaves get exposed, they eventually turn color.

The Sweet Gum Tree is famous for having a variety of autumn leaf colors on the same tree and sometimes on the same leaf.

Best Places for Fall Trees Color Display: Where and When Do the Leaves Change Color?

Clearly, this fall magic doesn’t happen everywhere. So, where can you experience these seasonal displays of colorful autumn leaves?

Part of Southeastern Canada and the Eastern United States have deciduous forests, and favorable weather conditions for magnificent fall colors.

Here is a table showing places to witness the fall color display and the best time to visit. A leaf tracker could aid in pinpointing the best time to visit.

Best Fall Plant Foliage in the USA

Below is the table featuring the best fall plant foliage in the USA:

The table presents an overview of the top fall plant foliage in the USA, along with the best time to visit and the various types of plants to expect during the fall season.

Best Fall Plants Foliage in the World

Below is the table highlighting the finest fall plant foliage from around the world:

Fun Facts About Fall Season

Here are a few fascinating facts about the fall season:

1. Shorter days than nights: There are more hours of darkness than daylight as we approach Winter Solstice (the shortest day of the year.)
2. Leaves on the trees will change color to orange, yellow, red, and brown.
3. Fall is the season of harvest.
4. This unique season has significant celebrations such as Halloween, Bonfire Night (UK), All Hallows’ Day, Thanksgiving (America), Michaelmas (Ireland), and more.
5. Bird migration: Birds that can’t survive living in cooler climates move to warmer places for the winter season. So, don’t be surprised to see large flocks of birds flying.
6. Fall also marks the beginning of the hibernation season. During this time, animals such as groundhogs and squirrels will gather food in preparation for winter.
7. Fall is the season after summer and before winter and beginning with the autumn equinox (when the sun passes directly over the equator, causing day and night length to be equal.)
8. The weather in fall gets colder and windy. The days and nights are of the same length, but gradually, the nights get longer and the days shorter.
9. The temperatures are also low.

Fall is a beautiful season to look forward to, not only for Halloween, milder weather, and pumpkins but, most importantly, trees changing color.

The leaf pigment, night length, and weather are the reasons why do leaves change color in the fall and dictate when the color transformation begins, how long it lasts, and the level of intensity of colors.

Frequently Asked Questions About Why Do Leaves Change Color in the Fall?