Why do fall leaves turn color?

Why do fall leaves turn color from bright green in the spring to rich reds and yellows in autumn? There are a few reasons that plants change ranging from day length to temperature signals that trigger trees and shrubs to slow production, drop weather-vulnerable leaves, and hunker down for winter.

In the spring, trees and shrubs grow new leaves filled with bright green chlorophyll that capture sunlight and feed plants with energy. When days grow shorter, these plants instinctively know colder weather is coming. They’ll shed their leaves to protect their branches from harsh weather ahead.

Understanding fall leaf color changes:

Day Length
- Shorter days signal to plants that a weather change is coming.
Plants Prepare by slowing chlorophyll production
- Green to Yellow: During the growing season, chlorophyll, the pigment responsible for the green color, dominates the leaves. As temperatures drop and daylight shortens in autumn, chlorophyll production slows and eventually stops. This allows other pigments in the leaves to shine.
- Carotenoids: These pigments produce yellow and orange colors. They are always present in leaves but are masked by chlorophyll until it fades.
Production of Anthocyanins:
- Red and Purple Colors: As chlorophyll breaks down, some leaves produce anthocyanins, pigments that create red and purple hues. This production is influenced by factors such as day length, temperature, and the presence of sugars in the leaves.
Temperature and Weather Impact:
- Cool Nights: Cool temperatures, especially during the night, can enhance the production of anthocyanins and intensify red colors.
- Warm Days: Sunny, warm days can lead to more vibrant colors as they increase sugar concentration in leaves, contributing to the red and purple hues.
Dry Weather
- Dry weather enhances fall colors.
Tree Species Differences:
- Maples: Known for their brilliant reds and oranges.
- Oaks: Typically show rich red, brown, or russet colors.
- Aspens: Offer a blast of clear yellow