Autumn colors brighten our landscape
Gold and orange, purple and crimson, some pinks and salmon and deep maroon. These are all colors we see each fall in parts of the country. As the season winds down, we are treated to an explosion of intense and radiant hues that shine like the most vivid sunset. How do the leaves know when to change and what gives each species the distinctive color it is known for? Autumn has definitely arrived and here in west Kentucky we're just starting to see the leaf show, when north of here the show is well underway and possibly over for those even further north. In warmer parts of the country, the show may not be as intense or even non existent. So, what happens and why do some leaves change color and others do not? Why are some years breathtaking and other years nothing to get excited about? It all comes down to chemistry.
What makes leaves change colors each fall?
The purpose of a leaf is to absorb sunlight to transform carbon dioxide and water to sugars which feeds the plant. This process is called photosynthesis and chlorophyll is the substance that allows the plant to absorb energy from light. And we all know that chlorophyll is the substance makes green leaves, however many people do not know that underneath all of that green, the autumn colors are already there. Carotenoids are what gives leaves the gold and yellow colors, just like fruits and vegetables. And just like fruits and vegetables, some species produce more. Maple trees, hickory trees and poplars have an abundance of carotenoids and that is why they have the deep golden and yellow leaves that shine so brilliantly. When the temperatures change and the direction and intensity of the sunlight shifts in autumn, the plants quit producing chlorophyll and the bright colors emerge as the green fades. Since the tree doesn't need to support the leaves once winter comes and it goes dormant, the leaves undergo a process where a small callus forms where they attach to the branch and they fall to the ground without causing harm to the tree. The nutrients left in the leaves enrich the soil, feeding the tree so it can produce more leaves in the spring.
Red autumn color depends on the weather
The red color, which gives us the brilliant scarlets, oranges and maroons is a bit different. The red family of colors depends on the weather for them to be at their best. Warm, sunny days and cool nights help the leaves produce flavonoids which are responsible for the reds and maroons. Moisture and temperature affect the intensity and early hard frosts will keep the show from being as bright. That has happened here in west Kentucky this year. We had a couple of very early frosts and the red colors are not as intense. Anthocyanins are produced when the sugars left in the leaves react with the sap and the results are the reds, purples and maroons. The intensity of each color is dependent on the acidity in the soil where the tree grows, so that is why colors are different depending on the location. The anthocyanins also blend with the carotenoids and we get a whole mixture of colors on the same tree and we see yellows, orange, purple and red sometimes on the same leaf. Some species produce more anthocyanins than others as well. The brilliant scarlet of the sumac and deep maroon of the dogwood are two good examples.
Go leaf peeping this autumn
Leaf peeping is a term used to describe the activity of traveling to locations known for glorious fall colors and the practice is one that people world-wide enjoy. New England is probably the most famous area to leaf peep, however, the upper mid-west, Canada and even Japan and parts of Asia have thousands of leaf peepers each autumn. The leaves in Europe change as well, however for some unknown reason, they are only yellow and gold with no reds or purples. We have wonderful color here in west Kentucky too, so the upper South is a great place to consider as well. We are about two weeks from full fall color, however the show is definitely starting. As long as you live in an area where the seasons change with the cool autumn nights, there is probably a leaf peeping opportunity. This is a great activity that families can do while staying out of crowds. There are a number of maps and graphs posted on the Internet showing where the colors are at their best. You can check them to see when the best time to visit would be. The autumn colors are a wonderful backdrop for family photos and it is even a great educational opportunity for those in an at-home learning situation. Enjoy the season and soak up some of the last rays of sunshine this autumn with a leaf peeping day for you and your family.
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