Why Are New Leaves a Lighter Color?

Why Are New Leaves a Lighter Color?
By Marcy Reynolds

Spring is a time of new growth at the Garden. While dazzling displays of colorful flowers easily catch the eye, I love seeing so many different shades of green on the trees and shrubs. Some of them almost look like they are glowing green! But why? With more sunshine and rain, plants grow, but why is the new growth light in color, while the existing leaves or needles look darker?

First, young leaves, or leaflets, are thinner than older leaves, allowing more light to shine through.

Second, young leaves are still developing. They glow green from the chlorophyll inside. Chlorophyll reflects green light, absorbing red and blue light. Older leaves also have chlorophyll, but as leaves mature they develop new pigments. This is what allows some mature or “adult” leaves to turn red, yellow and orange in the fall.

The new growth on some trees is not green. Some maples have red leaflets, for example. High levels of sugar cause this red or purple appearing color in the spring. The plant uses all the sugar to fuel new growth, causing the new growth to look red, while older leaves look green.

Now that you have learned about new and old growth on plants, challenge yourself to find the new growth on the plants in this photo series! Something fun I like to do this time of year is go out on a scavenger hunt to find new growth on plants at the Garden or in my neighborhood. I hope you can share what you have learned on your next walk!

To learn more, check out these links:

https://www.insidescience.org/news/spring-green-why-do-new-leaves-have-lighter-color

https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-light-dependent-reactions-of-photosynthesis/a/light-and-photosynthetic-pigments