It's Autumn, What's goin' On?
Well, I'm glad you asked that question!
But, in order to answer it we need to get just a bit technical here.
There are basically 3 things that cause leaves to change color in autumn: leaf pigments ( colors inside ), the length of night and weather.
When trees and other plants are actively growing in spring and summer their leaves are a nice color of green. This green color is known as "chlorophyll" and is produced during the process known as photosynthesis. This is the process whereby the tree takes in all this sunlight (together with adequate moisture) and produces sugars to feed itself. As the length of daylight shortens and the nights become longer (autumn) the trees and plants can no longer produce the same amount of chlorophyll (the green stuff) because there is less sunlight and therefore less photosynthesis going on. So they start thinkin' that they better be gettin' all of the sugar ( sap ) they can out of their leaves and branches etc. and down to their roots so they can make it through the winter.
Now, besides the green pigment being produced in the leaves there are also yellow pigments called "carotenes" which are busily at play throughout the year with the green chlorophyll. These carotene pigments are also the same yellow and orange colors that make vegetables like "carrots", corn, and bananas so yummy looking. Did I just say bananas were vegetables? Hmmm. Anyway, as the amount of the green stuff ( chlorophyll ) begins to decrease the other hidden colors of yellow ( carotene ) begin to emerge. It's kinda like dying your hair. If you cease putting on the same amount of color than the one or ones ( haha) underneath will start showing through.
In short, these hidden yellow colors begin to appear on trees such as Ginkgo, Redbud, Hickory, Birch and Tulip Poplar to mention a few.
So, what about the beautiful red and purple colors of the Red Maples and Dogwoods, the Red Oaks and Black Gum? Well, these particular trees also have other pigments called "anthocyanins" ( pronounced AN-THO-CY-AN-INS ) which are red and purple colors and hide the more subtle yellows. These anthocyanins also give the color to fruits such as cranberries, blueberries, strawberries, plums and red apples. The more sugar that is produced in a leaf the more anthocyanin that is produced. An autumn season with a bunch of bright, sunny days and cool nights will increase the production of the red/purple colors creating an even more spectacular fall display.
As for the tans and brown colors of some of the Oak trees. These hardwood trees produce higher levels of "tannins" ( brown in color )which kinda pile up in the leaves as the chlorophyll goes away. Tannins are a natural chemical found in tree bark, wood and tea and is used in the "tanning" process of animal hides turning them into leather. For you wine connoisseurs out there, it is also found in the seeds, stems and skins of many grapes especially those used in the production of red wines. The tannic acid is what makes you kinda pucker when you drink it or may even give you a headache.
Enough chatter about leather and wine. Did I say leather and wine? Hmmm!...Back to the trees! As for the spectacular fall colors it is also important to note that all of these yellow, red, purple, and orange displays will cease once ol' Jack Frost gets in the picture.
The leaves will then start to drop from the trees as the sugars make a drastic, last ditch retreat to the safety of their winter roots. Did I say "winter"? Hmmmm....I'd better get Ava to haul more wood up to the house.....hahaha...like that'll happen!
Anyway, that is pretty much how and why tree leaves turn their awesome colors. I hope this was not too technical and you were able to stay awake long enough to read it.
So, get out of the house, take a walk, or take a drive and enjoy Mother Nature's magnificent fall display while it lasts!
Ken
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