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Have you ever wondered why leaves change their colors in the fall?
Different cultures have answered this question in their own way.
One folk tale is that Jack Frost leaves beautiful patterns on the autumn leaves to mark his passing.
American Indian legends attribute the autumn leaf color to when the sprit hunters in the sky who slew the constellation “Great Bear.” The Great Bear was killed in the autumn, and his blood rained from the sky covering the forest changing its leaves to red.
Now we know through science that neither tale is true, but it is no less as magical that many trees change colors in autumn to create a visual tapestry across our land.
To understand what happens in the fall, we must look at the spring and summer when leaves make food for the tree through photosynthesis. This takes place in the leaf cells that contain the green pigment called chlorophyll.
Chlorophyll makes the leaves look green, and it does most of the work to turn sunlight into sugars.
During the warm temperatures and the long days many of our plants are green. So now we know why they are green, but what causes the different colors in the fall?
Because of changes in daylight and temperature in the fall, chlorophyll breaks down, and the green color disappears, replaced by other pigments. The yellows, reds, oranges or browns come from pigments called carotene.
The bright yellow of daffodils, orange of carrots and the red of tomatoes are from carotene.
Leaves that are red, wine-red, purple or blue come from pigments called anthocyanins, which make cherries red and cabbage purple. These pigments determine the shades of autumn color.
Shorter days and cooler nights truly create a magical time when trees receive nature’s messages to stop producing food.
Sugars that are left the tree draw back through the leaves to the stems and on through to the roots. This is how trees economize their food resources during the winter.
In the last act of its spectacular play, we finally find out how leaves change their color. As the last of the chlorophyll degrades, and the green color begins to fade, the leaf slowly prepares to let go of the limb, which triggers the veins in the leaf to narrow, trapping the last bit of sugars and pigments in the leaf and changing the leaves to autumn colors.
With all of that going on in a simple leaf, you would think the colors would be the same every year but they’re not.
As with all plants color is affected by soil moisture, day and night temperatures, sunlight and rain. Oh and don’t forget that each variety can react differently to each change.
One plant may have more color with more rain; another may have less. A warm, wet summer may delay fall for weeks, or as we have seen many times in our area, a hot dry summer can make the leaves change and drop early.
Some of you may look at fall leaves as a back-breaking chore to bag and put on the curb, but this year think of the miracle that leaf gave you this fall and thank it by creating a compost pile or using a mulching lawn mower to feed your trees so they can use those leaves as fertilizer to begin the whole process over in the spring.
For more information on this or any gardening subject contact the Johnson County Master Gardener Association www.jcmga.org or Pat Kriener 817-793-4625
Pat Kriener of Crowley is a Johnson County Master
Gardener and a
Wildbunch Writer.
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