So here come so catching up posts from the autumn. I'll try to do better!
Ontario Ministry of Natural Resources and Forestry
Leaves don’t “turn” orange or yellow. These colours are in the leaves all along. When plants shut down in fall, they stop photosynthesizing, and the green fades, letting the orange and yellow shine through. The orange is produced by chemicals called carotenes, which also make carrots orange.
So what about red and purple leaves? Some trees and other plants, such as red maple and sumac, produce chemicals called anthocyanins that produce vibrant red or purple leaves in response to weather cues in fall. These chemicals are the same ones that give colour to red apples, purple grapes, and blueberries!
Orange leaves can also be caused by carotenes and anthocyanins mixing it up. In some sugar maples, you can see a range of colour from yellow to brilliant orange to red in the same tree, depending on how much sunlight the leaves received, which affects how much anthocyanin they produce.