Fall (Autumn) provides a welcomed relief from the heat of summer with cooler days and nights, plus autumn gives us something no other season does- a change in tree foliage colors. Many people plant a maple tree with hopes of watching it turn red in autumn. It’s very disappointing when the leaves don’t turn red.
Most of the time it is not your fault if the leaves of your maple tree don’t turn red. The foliage color in autumn, or lack thereof, is at the mercy of the weather.
Leaf Color Change Process
A tree’s leaves are green throughout the spring and summer because of chlorophyll. This substance is bright green and hides the molecule colors that also are present in the leaves. In autumn, deciduous trees like maples break down the chlorophyll into smaller molecules. Then they send these molecules to the roots for storage until spring.
As the chlorophyll molecules exit the leaves, the leaf color changes. When new leaves emerge in spring the chlorophyll is reconstituted and sent back up the tree and into the leaves.
The red leaf color of the maple tree comes from anthocyanins which are manufactured as the chlorophyll is begins to break down in early autumn.
Weather Impact
Rainy, overcast days during autumn cause the chlorophyll to break down more quickly and increase the yellow and orange leaf colors.
Early frosts reduce the amount of red pigmentation. A sudden cold snap can turn the maple leaves brown overnight. Also, overly warm autumn weather will delay the foliage color change and cause the red pigmentation to be dull and pale.
Stress will also prevent the leaves from turning red. Lack of nutrients, not enough moisture, or injury will cause the tree stress. Feed maple trees in the spring and water them during times of drought in the summer.
The best weather for leaf color is cold nights and bright, sunny days. Normal rainfall also stimulates the production of the red-pigmented anthocyanins.
Incorrectly Labeled
Red maples (Acer rubrum) are prized for their spectacular red foliage color in autumn. But if the leaves of your maple tree have never turned red in autumn, then there’s a good chance the tree was mislabeled at the tree farm or nursery.
Red maples have numerous cultivars, many of which feature yellow foliage even though they are called red maples. If your red maple turns bright yellow in autumn, it was probably incorrectly labeled and is one of the many golden cultivars. There’s no changing the leaf color, just learn to love yellow.
Check out my other article on autumnal colors here.
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