After posting last week’s beauty/fluffy blog on October, I started looking around and wondering why some trees of the same genus (i.e.: maples, oaks, aspen...) are still green while others are already fully clothed in their colorful splendor. I’ve probably thought about this every autumn over the years, but since we can look up everything under the sun now – and over it – I did.
Except for the differences between the different types of trees, I never found an answer to my question. So I’ve decided to go with logic and guess that perhaps the young trees or less strong trees may turn the earliest. The stable trees may be able to withstand the key environmental changes longer. This is somewhat logical if you think about how perennial plants, including deciduous trees, survive winter temperatures. Plants have learned to survive by either toughening up or by shedding their tender leaves and sealing their ends. (Huh. I wonder if there is some wisdom in this for us peoples...)
I’ll share a few of the informational tidbits I did come across for a better understanding of why the leaves change – and perhaps we'll find some more logic along the way.
Three factors influence the autumn leaf colors: leaf pigments, the length of night (declining intensity of sunlight) and weather. According to the Forest Service/U.S. Department of Agriculture, the leaf colors change primarily because nights become longer and colder, causing a biochemical process.
Chlorophyll enables plants to use sunlight to create their own food and makes their leaves green. In autumn, Chlorophyll production slows to a stop as the days become shorter and temperatures drop, allowing the other pigments in the leaves to show. There are two primary pigments. First are carotenoids. Sound like a carrot? That’s because this pigment produces orange, yellow, and brown colors. Anthocyanin pigments create the reds.
The carotenoids (orange pigments) are present in leaves year-round, so their color changes in the fall are predictable. Whereas, the anthocyanins (red pigments) are created in the fall in response to light, plant chemical changes, temperature, and water supply. These are the trees that influence the brilliance of the fall color display based on the weather. The best weather for fall foliage colors is a chain of warm, sunny days and cool, crisp, but not freezing, nights.
Moisture can also affect the colors. A late spring or a severe summer drought can suspend the onset of fall colors. A warm, wet spring, normal seasonal summer, and a warm, sunny fall with cool nights should cause the most brilliant colors.
Dropping their leaves causes them to seal up their ends, so the cold doesn’t destroy them. That’s why our fruit farmers dread a too-early spring. If the buds come out before winter or hard frosts are done, they can lose entire orchards.
Then the really big question: why don’t evergreen trees change color and drop their leaves/needles? It’s because they were established and brought in from colder climate areas that gave them the shape and texture of their needles. These needles allow them to hold maximum moisture and nutrients in order to survive the winter months.
I’ll be keeping an eye on the red trees to see if they are the trees that I have noticed are inconsistent with their turning timing. Anthocyanin pigments (reds) could be the culprit! I may have gotten my answer after all.
Happy trolling along on your color tours!!
Forest Service/U.S. Department of Agriculture; Gardenista; North America Tree Service
These pictures were taken on the same day about a week ago. (Posted:10/21/22)
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