Enjoy All The Colors of Autumn and Fall!

It is sinking in that fall is here and all around us.  A few pretty cool nights make it clear that the first freeze for central Oklahoma could be close at hand.  Our friends at Woodward and throughout the Oklahoma Panhandle got a light freeze earlier this week so our time is coming.  It could be in the next week or it could be a month but the clock is ticking on all of our pretty annuals, the warm season vegetables and the foliage on our deciduous trees.  This is one of my favorite times of year as we enjoy the last hurrah of the warm season crops and their flower colors get more intense with the cool night temperatures.  We enjoy the fall decorations of hardy mums, pumpkins, hay bales and corn stalks.  We enjoy the colors of the fall and winter crops that can be planted now including ornamental kale, ornamental cabbage and the charming pansies, which are the leading stars of the Oklahoma winter garden.  This is the season to sow your tall fescue or ryegrass seed if you want a green winter lawn.

One of the best things about fall that complements the football games, time by the crackling fire pit and the pretty fall flower shows is the annual dance of fall color on our deciduous trees and shrubs.  This show is never the same from year to year because it depends on the temperature and weather patterns, day length and moisture in the ground.  The fall color is triggered by day length as the days get shorter and the sunlight less intense so that the deciduous trees and shrubs know that winter is coming and start to prepare for winter hibernation.  The timing and amount of color and intensity of fall color all depend on the weather patterns – how early we get cold fronts, how cold, for how long and by how much moisture is in the root zone.  Fall color will be different in a drought year than in a year with good moisture.  If we get a really hard freeze early we will jump to leaf drop and miss much of the fall color show which is best in years with good sunlight, decent soil moisture and gradually declining night temperatures which allow the symphony of leaf color change to go through their full fall song and dance.

As autumn progresses the trees start pulling extra sugars and carbohydrates down into the branches and roots to store for winter.  Three pigments are involved in autumn color.  Chlorophyll is the green color we see throughout the growing season and it is the building block that converts sunlight and water into sugars for food for our plants.  Carotenoids are pigments that produce the yellow, orange and brown tones we see in carrots, corn, bananas and daffodils and are present in all plant cells all year but are concealed or masked by chlorophyll for most of the year.  Anthocyanins produce the reds and blues we see in grapes, red apples, blueberries, cherries, plums and strawberries.  They are produced in most plant cells only in the cooler weather of fall by the excess plant sugars in the leaf cells and bright fall sunlight.  Chlorophyll production slows down and then stops as fall progresses.  As the green chlorophyll disappears from the leaf we get to see the carotenoids or anthocyanins that are still in the leaf cells and give us the yellow, orange and red colors that announce autumn to us.   Poplar trees give us bright yellow leaves before they drop and Oaks give us red leaves and brown colored leaves.  Maples give us yellow, orange – red or brilliant red depending on the species. These leaves will eventually fall where they can provide natural mulch to your yard, be collected and composted to add to your soil and help continue the circle of life.  We hope the hard freezes are delayed and we get to enjoy a long and colorful fall.

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