Why Do Leaves Change Color?

KATIE GRANT

Katie Grant is a publications supervisor in the DNR’s Office of Communications. Activity courtesy of Malia Hollowell, a lesson planner and curriculum designer. Her blog, PlaydoughToPlato.com, is a resource for pre-K through first-grade teachers to save time, stay inspired and give every student bigger results.

Ever wonder why leaves change color in the fall?

Leaves need sunlight, air, water and chlorophyll (green pigment) to make food for a tree. Since chlorophyll is the dominant color during the spring and summer as leaves absorb as much sunlight as they can, the green color hides all the other colors in the leaf.

As autumn rolls around, the days are shorter, the nights are longer and temperatures start to get cooler.

When this happens, trees start to produce less chlorophyll, eventually producing none at all. As the chlorophyll fades, other colors such as red, orange and yellow — which have been there all along — start to show.

Want to experiment at home? Try this simple chromatography activity so you can see just what gives leaves their amazing fall colors.

• Leaves

• Mortar and pestle (or a spoon)

• Glasses or jars (one for each leaf color)

• Rubbing alcohol

• Large pan or heatproof dish to hold the glasses/jars

• White coffee filters

1. Tear up a leaf and place it into a mortar, crushing it with the pestle to release the leaf’s juices. Transfer the leaf pieces and any liquid into a glass. If you don’t have a mortar and pestle, put the pieces into a glass and crush them with the back of a spoon.

2. Repeat this process with all your leaves, placing each one in its own glass.

3. Carefully pour 1-2 tablespoons of rubbing alcohol into each glass until the leaf pieces are covered.

4. Have an adult help you boil water. While it’s heating, set the glasses in your pan. Pour the water into the pan or heatproof dish so the water is surrounding the glasses but not

in the glasses. The goal of this is to warm up the rubbing alcohol mixture in each glass. 5. Let sit for at least 30 minutes. 6. Cut the coffee filter into strips (approximately 1 inch by 5 inches). Place one end in the rubbing alcohol mixture and drape the other over the edge of the glass or jar and outside the dish, being careful to keep it from touching the water in the dish.

7. Patiently wait at least 1-2 hours, or overnight.

8. Pull out the filter strips to see what happened with each one. The alcohol will carry the pigments from the leaves and up the paper, separating them into bands of color.

What colors did you end up with?

Did the leaves have just one pigment in them or several?

Let us know what you find by emailing your results to dnrmagazine@ wisconsin.gov.