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Leaves Changing Color

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Friday, November 15, 2019 - 7:00am

Announcer: Farm and Family is a production of the Mississippi State University Extension Service.

Amy Myers:  Today we're talking about why leaves change color in the fall. Hello, I'm Amy Myers, and welcome to Farm and Family. Today we're speaking with John Kushla, Mississippi State University Extension Forestry Specialist. John, why do leaves fall off of the trees this time of year?

John Kushla:  Amy, deciduous plants are those perennials that drop their leaves in the autumn, giving us the nickname fall for this time of year. These plants have what we call expendable leaves. They are broad and thin and succulent, but, because of this, they do not resist freezing. Evergreens, on the other hand, have very well made leaves that endure through the winter. Many have needle-like shape and waxy coatings and fluids that resist freezing. Some may even be retained for more than a year, such as with pine or Southern Magnolia.

Amy Myers:  Why do leaves turn color?

John Kushla:  Chlorophyll is the molecule that enables plants to combine water and carbon dioxide to make sugars through photosynthesis. Chlorophyll absorbs light in the red and blue range, and so green light is reflected and the leaves appear green. In the fall, though, deciduous plants start preparing for dormancy. To reduce moisture loss, deciduous plants form an abscission layer at the base of the petiole or stem of the leaf. This reduction in water flow to the leaf stops chlorophyll production and sunny weather further reduces the amount of remaining chlorophyll by breaking it down. Consequently, of all of this, we begin to see other leaf pigments, carotenoids, which are yellow to orange; anthocyanins are sugars with red to purplish color; and tannins, which are Brown in color.

Amy Myers:  What triggers the leaf color change?

John Kushla:  Although we respond to the cooler temperatures this time of year, plants are responding to shorter day length. The shorter days initiate the physiological changes preparing plants for dormancy during winter. To a plant, the cooler temperatures are a coincidence, but not the cause.

Amy Myers:  What conditions help produce brilliant fall colors?

John Kushla:  Warm, sunny, dry weather and cool nights will produce the most brilliant fall colors. This enhances sugar production, but the cool nights restrict sugar flow out of the leaf. On the other hand, cloudy, rainy fall weather tends to reduce color intensity. Summer droughts can affect soil moisture, which can delay fall coloration in general.

Amy Myers:  What else accounts for the different colors in fall?

John Kushla:  Beside the physiological changes going on within every plant, each species has its own particular fall coloration pattern. Black gum, dogwoods, sourwood, and sumac are usually among the first species to turn color, whereas okas tend to turn later. Cottonwood, hickories, and yellow poplar turn a golden yellow. Dogwood and red maple become brilliant crimson or Scarlet. Oak trees turn russet or maroon and eventually brown, whereas sweet gum turns very [inaudible 00:03:36] colors from golden yellow to russet to maroon.

Amy Myers:  Now, where and when is the best viewing of fall colors in Mississippi?

John Kushla:  Go where there are mixed hardwood forests. These would include hickories, maples, and sweet gum, which have vibrant colors that last, whereas oaks tend to turn color briefly before becoming brown. All along the Natchez Trace Parkway or Tenn-Tom Waterway are good viewing sites as well as Tishomingo County on the edge of the Appalachians. A greater predominance of hickories and other hardwoods are found there.

Late October through mid-November fall's colors begin in Northern Mississippi and gradually progress southward. If you have any questions, call your local county extension office or me at 662-566-8013.

Amy Myers:  All right, thank you so much, John, glad to know why all of this happens. Today we've been speaking with Dr. John Kushla, Mississippi State University Extension Forestry Specialist. I'm Amy Myers and this has been Farm and Family. Have a great day.

Announcer: Farm and Family is a production of the Mississippi State University Extension Service.

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