Why Leaves Change Color: Fall Science for Grades 1–3

Fall is one of the most beautiful times of the year — the air gets cooler, pumpkins pop up on porches, and the trees turn bright shades of red, orange, and yellow. But why does this happen? What causes green leaves to suddenly change color?

This simple question opens the door to a rich science lesson for students in kindergarten through third grade. It blends observation, nature, vocabulary, and even art. Whether you’re teaching full-time or filling in for a day, this is a fall science topic that kids will love — and remember.

What makes leaves green?

During the spring and summer, leaves are hard at work making food for the tree. They do this using a process called photosynthesis, which means “putting together with light.”

Leaves contain a special green chemical called chlorophyll. Chlorophyll captures energy from sunlight and uses it to turn carbon dioxide and water into food. That food feeds the tree and helps it grow strong.

Because leaves are filled with chlorophyll, they look green to us during the warm months.

What happens in fall?

As summer ends and fall begins, the days get shorter and cooler. The tree starts to prepare for winter. Since there isn’t as much sunlight in the fall and winter, the tree doesn’t need to make as much food. So it begins to shut down photosynthesis.

As chlorophyll fades away, it reveals the colors that were already in the leaf all along — like yellow and orange. These colors come from other natural chemicals in the leaf:

• Carotenoids make yellow and orange (like in carrots!)

• Anthocyanins make red and purple colors (like in apples and grapes)

The green disappears first, and the other colors slowly shine through. Eventually, the tree lets go of its leaves altogether, saving energy during the cold season.

How to explain why leaves change color to kids

You don’t need fancy science terms to make this lesson stick. Here are some easy comparisons and kid-friendly metaphors:

• “Chlorophyll is like a green coat the leaf wears in summer.” In fall, the coat comes off and we see the colors hiding underneath.

• “The tree is going to sleep.” As winter comes, the tree rests — it doesn’t need to make food anymore.

• “The leaf is like a battery.” When it’s full (in summer), it does work. In fall, it powers down.

Visuals help a lot! Real leaves, drawings, and movement all reinforce the ideas.

Hands-on classroom activities

Here are some fun and meaningful ways to explore fall leaves and color change with young learners:

1. Leaf Hunt + Sorting

Go outside and collect leaves in different colors, shapes, and sizes. Back in the classroom, have students sort them by color, type, or size. Create a class chart or collage.

2. Crayon Rubbings

Place leaves under thin paper and rub crayons or colored pencils across the top. This shows the structure and veins of the leaf — and gives students a tactile connection to the science.

3. Leaf Color Change Art

Start with green construction paper leaves. Let students “paint” on fall colors (tissue paper, watercolor, dot markers) as if the green is fading and new colors are emerging.

4. Simple Leaf Booklet

Have students create a mini-book:

• Page 1: What leaves look like in summer

• Page 2: What happens in fall

• Page 3: The colors we see

• Page 4: Why leaves fall off

5. Time-lapse Videos

Show a short time-lapse of a tree changing through the seasons. Pause and ask students what they notice. Ask, “What’s changing? Why?”

Vocabulary words to introduce

These terms are great to introduce gradually throughout the lesson:

• Leaf – the part of the plant that catches sunlight

• Chlorophyll – the green stuff that helps the plant make food

• Photosynthesis – how plants use sunlight to grow

• Fall / Autumn – the season when leaves change color

• Carotenoids – chemicals that make orange/yellow

• Anthocyanins – chemicals that make red/purple

You don’t have to explain every scientific term in full — just using the words in context helps build understanding.

Bonus writing or discussion prompts

Wrap up your leaf lesson with a creative writing or speaking activity:

• “If I were a leaf in fall, I would turn ______ and feel ______.”

• “What would you do if you changed color like a leaf?”

• “Write a story about a leaf falling off a tree and where it goes next.”

These types of open-ended questions spark imagination and reinforce comprehension.

Why it matters

Learning about why leaves change color teaches more than science. It encourages students to observe, ask questions, and notice the world around them. It’s a perfect fall topic that connects to weather, seasons, plant life cycles, and even emotions (change, letting go, resting).

And for substitute teachers? It’s a seasonal hit — easy to teach, fun to discuss, and guaranteed to engage the room.

The next time a child picks up a red or yellow leaf, they’ll know there’s science behind the beauty — and that’s the power of good teaching. Whether you’re reading a book, taking a walk, or doing an art project, explaining why leaves change color turns a simple fall day into a hands-on science lesson.