Welcoming In A Beautiful Oklahoma Fall! Autumn Trees & Shrubs Showing Their True Colors!

Welcome to autumn in Oklahoma with beautiful warm afternoons and crisp cool mornings.  We are about two weeks away from the average date for our first light freeze in central Oklahoma.  Enjoy these last days with your annuals, snap pictures and capture memories of the bright colorful flowers and vegetables you want to remember as you plan your future landscapes and container gardens.  We often end up with some “Indian Summer” weather after the first light freezes and tender plants in protected areas or that you cover and protect with row cover, sheets or boxes may survive these first bouts of cold weather and still perform for up to another four to eight weeks until we get really hard freezes down in the low to mid twenties.  Your cool season veggies like broccoli, cauliflower, kale, cabbage, some root crops and leafy green crops and many cool season flowers like pansies, and viola will  keep growing and flowering for many weeks or even though most of winter depending on the weather ahead.

The star of fall gardening is the show of color from our deciduous trees and shrubs as they change color and then fall to the ground ready to become compost.  Some trees are certainly more exciting to watch than others and conditions vary from year to year depending on the soil moisture, humidity, daytime and nighttime temperatures and sunny days versus cloud cover days leading up to fall color season.  Day length is the main trigger for leaf color and leaf drop as the trees and shrubs sense the shorter days and lower intensity of sun for fewer hours each day.  These light signals trigger the tree to start storing sugars and carbohydrates for winter and to start reducing photosynthesis or food production activities.  Photosynthesis is powered by the sun but chlorophyll is the secret sauce that powers the conversion of solar energy, water and nutrients, inside the plant cells to produce sugars.  As the basic green of the chlorophyll is removed from the leaf, the other colors become visible.  Carotenoids product the yellow, orange and brown colors we see in fall leaves.  These are the same colors we see regularly in corn, carrots, bananas, marigolds and daffodils.  Anthocyanin is the plant pigment that results in red, blue and purple color tones.  We regularly see anthocyanin at work in red apples, cranberries, blueberries, strawberries, plums and grapes.  Anthocyanin is generally produced in the fall in response to excess sugars within the leaf cells and is water soluble and is actually in the liquid of leaf cells.  Chlorophyll and carotenoids are present throughout the whole growing season but the green color of chlorophyll dominates or hides the yellow carotenoids until the long nights of fall as the chlorophyll wraps up its work for the season.

In our region, poplars produce the most yellow fall foliage while oaks produce red, brown or russet colors, some maples with higher sugar levels like red maple, Caddo maple or sugar maple produce orange red or even scarlet foliage.

The veins that carry fluids from the roots into and out of the leaf gradually close off as the days get shorter and a layer of cells form at the base of each leaf that leads to falling leaves. These clogged or stopped off veins trap sugars in the leaf and the amount and type of those sugars and pigments determines the fall leaf colors.  If there are enough sugars trapped, that will promote production of the anthocyanin and the more dazzling orange and red colors.  We get the best color with warm sunny days and cool, crisp but non-freezing nights as the chlorophyll winds up its work for another growing year.

Enjoy the fall color in your yard and neighborhood, local parks like Will Rogers Arboretum in Oklahoma City or plan a family trip to forested areas like the ever popular Talimena National Scenic Drive though the Ouachita National Forest of Southeast Oklahoma.

Don’t forget to be buying and planting pansies and violas to enjoy all winter and spring flowering bulbs like daffodils, tulips, hyacinths and crocus so you can enjoy their color early next spring.


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