Why Does a Maple Tree Start Turning Color & Losing Its Leaves in Early August?
Maple trees (Acer spp.), a lovely addition to yards and gardens, thrive in U.S. Department of Agriculture plant hardiness zones 5 through 9. Specific hardiness zones vary for different varieties of maple trees. Maple trees contribute to beautiful fall foliage displays. If you see a maple tree turning red in summer, it may be experiencing stress.
If a maple tree turns color and loses its leaves in summer rather than fall, it could be a sign of stress due to heat, drought, disease/pests, or damage caused by any of the former.
Photosynthesis and Maple Trees
Generally, plant cells produce chlorophyll, which is a pigment necessary for plant food production through photosynthesis. However, this process requires warmer temperatures. Fall's lower temperatures and reduced amount of daylight mean that deciduous trees must rely on secondary pigments, such as xanthophylls and carotenoids, Scientific American reports, to conduct photosynthesis. While chlorophyll is green, these other pigments give leaves yellow and orange hues.
Many kinds of maple trees exist, including sugar maple (Acer saccharum), red maple (Acer rubrum) and silver maples (Acer saccharinum), among others, the University of Vermont Extension notes. Maple trees – especially red maple trees, the National Wildlife Foundation says – are known for their vibrant red autumn leaves. According to Cool Green Science, maple leaves turn red because of anthocyanin production. In fall, when the connection between the stems of maple leaves and the tree’s branches is discontinued, leftover glucose (a simple sugar) gets trapped in the leaves and promotes anthocyanin production. The production of this pigment may offer the tree a few different benefits, including frost protection and sugar provision, before and during its winter dormancy.
Maple Trees Turning Color Early
If a maple tree starts turning color and losing its leaves before fall, it may be a sign of stress. According to the Michigan State University Extension, stressed maple trees will turn color and lose their leaves early. Spider mites can cause stress in maple trees, which can be a particular problem for trees planted near sidewalks, driveways or walls, which are exposed to significant reflected heat (hot conditions invite mite infestations).
Damage to the trunks of maple trees from mowing, animals or disease also can inhibit the transport of water and nutrients throughout the tree, causing stress and premature leaf color changing and dropping. Stress from drought can also cause a maple tree to turn red in summer. Watering and mulching heat- or drought-stressed maple trees can sometimes remedy the issue. Trees significantly harmed by drought may take one or a few years to recover, or, if severely affected, they may not recover at all.
Year-Round and Springtime Red Leaves
In addition to maple leaves turning red in summer, you may notice the leaves turning red in spring, which is usually normal. Maple trees are a type of hardwood tree, and, as Northern Woodlands describes, hardwood leaves are typically red-hued when they first emerge in spring. After emerging, the leaves gradually become greener as they produce chlorophyll, which requires sunlight and warmth. If new leaves experience a cold snap or extended cloudy days, chlorophyll production will stall and the leaves may stay redder longer.
Some maple trees leaves are colors other than green, not only in autumn. According to the Arbor Day Foundation, summer red maple trees (Acer rubrum ‘HOSR’) produce burgundy-red leaves in spring that become dark purplish-green at maturity. They change to shades of orange, yellow and purple in the fall. Crimson king Norway maple trees (Acer platanoides ‘Crimson King’) have purple-green foliage during the summer months that turn brown, bronze or dark maroon in the fall, the Forest Service Department of Agriculture notes.
- Scientific American: Find the Hidden Colors of Autumn Leaves
- National Wildlife Foundation: Red Maple
- Cool Green Science: Fall Foliage - When, Why & How Vibrant Will Maple Leaves Be?
- Michigan State University Extension: Early fall color in trees and shrubs may be a sign of stress
- Northern Woodlands: Why Do Leaves in Spring Sometimes Appear More Red Than Green?
- The Arbor Day Foundation: Summer Red Maple
Elizabeth Perry is a writer and editor. She graduated with honors from Vassar College in 2013, earning her BA in English and specializing in literature and literary theory. She is a lover of sustainable agriculture and self-reliance, and has experience gardening and farming, including on a flower farm. She has contributed creative writing, arts journalism, and literary criticism to a variety of publications, both in print and online.