Tuesday, October 11, 2011
The Joy of Autumn!
Hi everyone! I feel so lucky to live here on the east coast of the US for several reasons, but my number one reason is the changing of the seasons that we enjoy here in Delaware. The burst of colors and growth in the spring, the bright, vibrant colors of the summer, and yes, even the snowy days of winter make living here so wonderful, but my favorite season of the year must be autumn when the landscape around us is getting ready for a long winter sleep so we can have that gorgeous green of spring each year. Why is autumn my favorite season, you ask? First and foremost is the knowledge that this is the time that plants begin to shut down and ready themselves for the long winter ahead. Perennial plants die back to their roots, annuals spread their seeds in anticipation of a new generation before dying, and trees and shrubs show off their wonderful colors that lurk under all that green produced by their chloroplasts. Yes, I know, this is a magical time of year but what is even more magical is what really happens when the reds, yellow, oranges and browns of autumn make our forests and fields so beautiful that people will actually take vacations to go 'leaf peeping'.
But what 'makes' the trees turn color? What happens to the leaves to make them 'turn colors'? How does this happen? All good questions and I hope I can answer a few of them today!
Why do trees and shrubs turn colors? Have you ever noticed that no matter what weather does in the fall, the leaves of trees and shrubs start to turn colors and fall off always around the same time each year? September and October temperatures can be in the 80s but the leaves always begin to change color or fall off the trees. Is it so the 'leaf peepers' can book their vacations for the same week year after year? Does the amount of rain in the spring and summer affect the timing of this change? Well, the actual ways and means of color change in trees and shrubs, and some perennial plants, are complicated and include many chemical and biological processes inside the plant. The actual processes and cycles are not important to those of us who love to watch the leave turn colors and simply put, most deciduous plants follow a biological timeline that is based on day length. Long days and short nights help plants to grow while short days and long nights cause plants to begin to shut down growth and ready themselves for a long winter sleep. The green that you see in plant leaves is a result of the huge amounts of chlorophyll being produced during the spring and summer by the chloroplasts that are present in all growing plant cells. There is so much chlorophyll being produced that it masks the other colors that are always present in all plant cells.
Carotenoids are present in the chloroplasts along with chlorophyll and produce the yellow, orange, brown colors in fruits and flowers like bananas, daffodils, corn, and carrots. These colors can be readily seen in fruits and flowers because they are part of the reproductive system and not the vegetative system, and don't produce chlorophyll in their cells.
Anthocyanins, flavonoids that give red apples, cranberries, blueberries and plums their blue/red colors are found in all plant cells but increase dramatically in leaves during the fall months in response to large amounts of stored sugar in the leaves and the bright light of fall.
So, as the days get shorter and the nights get longer, chlorophyll production is reduced and the sugar that accumulates in the leaves begin their trip down to the roots for winter storage. Leaf veins begin to close up and the overload of sugar eventually becomes 'stuck' in the leaves as the veins shut down. This over-abundance of sugars in the dying leaves causes the anthocyanins to go into overtime production and suddenly leaves begin to turn red, crimson, and purplish/red. As chlorophyll production decreases, the colors of carotenoids become apparent and suddenly trees and shrubs are covered in bright reds, yellows, oranges and every color in-between.
Other conditions must be present for good fall color, including good rainfall in the summer and early fall. This allows for excellent sugar production and increases the red and purple colors of fall foliage. Good sunlight and cool nights can help the increase of yellows and oranges, but daylight length is number one in the production of this wonderful show that Mother Nature puts on every fall.
So...the next time you look at those wonderful fall leaves or pick up a bright red maple leaf or wonder at the beauty of a yellow hickory leaf - remember how those wonderful colors were produced - and realize how magical a plant really is to the planet. Not because of the colors of the leaves or how it looks in our landscape, but how it keeps us alive by producing all of that sugar and oxygen that keeps us eating and breathing every day.
Magic is magic even when you know how it happens!
Until next time - get out there and enjoy the world around you!