Why do leaves change color?
Why Fall Leaves Change Color Plus An Experiment For You!
Okay, give me 3 reasons why leaves change color in the fall?
C’mon, real quick and no Googling it!
I remember in grade school learning something about how the shorter days of light in the fall was the reason and heard the stories about colder temperatures. Each year, we speculate on when the leaves will begin changing and will it be a good season of color or not – exactly what does influence that?
Here, is another thing that has stumped me, what trees give out what color?
And, is there an experiment you can do in the summer to determine what their color will be in the fall? That sounds like a fun workshop we should do for families staying with us!
Turns out you can!
So in believing that blogs should be this journey where we explore together, I decided to investigate this. If you have info on why leaves change color or know of on-line resources let us know!
As I was doing research, I came across a resource I was familiar with during my days working on sustainable development in the Park. “SUNY ESF” short for the state college system in New York, this one for Environmental Science and Forestry.
In an article entitled, appropriately enough, “Why Leaves Change Color,” (https://www.esf.edu/pubprog/brochure/leaves/leaves.htm.
Text prepared by Carl E. Palm, Jr. ), it turns out my memory was correct, and light and temperature do play a role. Calling the spring and summer a food “factory” produced through a tree’s leaves, they are green due to chlorophyll. We have all heard about the importance of mother nature absorbing our carbon dioxide.
Does it happen to you too where subjects you found boring in high school, are now fascinating? Is that a sign of maturity or old age when things right in front of you, that have been going on since you were a kid, suddenly become interesting, even mysterious and glorious?
Maybe it is not a an old age thing, as I am amazed at all the texts my kids do with each other all day about simple stuff like driving conditions, the weather and yet they are stumped when I ask them why do leaves turn color or, do they know each other’s class schedule? How am I supposed to plan Thanksgiving?
According to the ESF article, the fall colors we see now, are already in the leaves in pigments called “carotenes” and “xanthophyll” which “give the orange color to a carrot.” Carotenes and “carrots?” Is there a word connection there?!
Anyways, they are dominated by the green producing chlorophyll cells of a leaf. In the fall as the days get shorter and colder, the food factory “leaves” (okay, bad pun) or shuts down. You know, sort of what happens this time of year when the Northeast population “leaves” to sunny Florida.
As this cycle breaks down, all the colors get mixed up. It’s like Chef Cathy’s blender with her fall blueberries found on the property that she mixes in with her famous muffins to create different shades of hues. Depending on the tree, different blender action gives off various colors. Some I do know, like sugar maple is orange, birch a yellow, oak is brown.
Here is what I didn’t know.
There is a whole lot more going on. For example the ESF article points out why do leaves eventually “fall” (I can’t help myself)? Additional cells arrive on the scene and “gradually severs the tissues that support the leaf” causing it to…you got it, “fall.”
The magic isn’t done, as the tree performs surgery on itself, covering up the area where the leaf was attached as it awaits the cold winter before it begins the cycle again. Talk about turning over a new leaf.
And yes, you can predict how the foliage season will come to light (I couldn’t resist that one either). Weather does play a role on what you will see and how spectacular it is. In an article, “Using Indicators Determining Great Autumn Tree Color” by Steve Nix (https://www.thoughtco.com/predicting-fall-color-autumn-leaf-display-1342825 Predicting Fall Color and Autumn Leaf Display), too much of a good thing is bad. “The more leaves attached to trees entering the color season means more to look at. Droughty summer weather conditions can limit that volume but a wet summer can set up disease and insects.”
The ESF article points out that frost brings out the color but if it happens too early, it dampens the parade. Rain, as it does for the vibrance of our gardens (as long as it is not too much!) brings out their true colors. Perhaps nature’s way of reminding us when things are rainy, true character comes out.
But, here is a cool thing and I want to do this next summer as a fun workshop. During the height of the green colors, you can tell what color they will be in the fall – and even what kind of a foliage season it will be! In a process called chromatography, you can break down or separate the pigments in a leaf like nature does in the fall.
Now, I don’t want to give it all away now, so as to save the surprise for your summer visit, but it is amazing on how simple it seems to be. I haven’t done it either but looking forward to trying. In the meantime, you might want to get some kind of glass container, rubbing alcohol and filter paper! And then you can be in our summer newsletter telling folks about your fall foliage predictions!
SUNY College of Environmental Science and Forestry
https://www.esf.edu/pubprog/brochure/leaves/leaves.htm Why Leaves Change Color
...as featured on weather.com The Splendor of Autumn very autumn we revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter. During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.
Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are masked by great amounts of green coloring.
Chlorophyll Breaks Down
But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.
At the same time other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.
The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.
Other Changes Take Place
As the fall colors appear, other changes are taking place. At the point where the stem of the leaf is attached to the tree, a special layer of cells develops and gradually severs the tissues that support the leaf. At the same time, the tree seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight, it leaves behind a leaf scar. Most of the broad-leaved trees in the North shed their leaves in the fall. However, the dead brown leaves of the oaks and a few other species may stay on the tree until growth starts again in the spring. In the South, where the winters are mild, some of the broad-leaved trees are evergreen; that is, the leaves stay on the trees during winter and keep their green color.
Only Some Trees Lose Leaves
Most of the conifers - pines, spruces, firs, hemlocks, cedars, etc. - are evergreen in both the North and South. The needle- or scale-like leaves remain green or greenish the year round, and individual leaves may stay on for two to four or more years.
Weather Affects Color Intensity
Temperature, light, and water supply have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. The best time to enjoy the autumn color would be on a clear, dry, and cool (not freezing) day.
Enjoy the color, it only occurs for a brief period each fall.
Text prepared by Carl E. Palm, Jr.
What causes good fall color?
“Anthocyanins” are the pigments responsible for red and purple fall leaf colors. These are only produced in the fall when sugars are trapped in the leaves. They function similar to the carotenoids, and help the leaf use up any remaining energy as chlorophyll disappears.
How could you predict the color of a tree leaves will turn in fall?
In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. ... This project will expose the hidden colors in a green leaf and predict what color it will be in the fall!
Chromatography with Leaves: A Nature Study Experiment What is chromatography?
It’s simply a big name that means separating mixtures. Or, in this case separating pigments. As complicated as the word sounds, experimenting with chromatography is very easy.
https://www.thoughtco.com/predicting-fall-color-autumn-leaf-display-1342825 Predicting Fall Color and Autumn Leaf Display
Using Indicators Determining Great Autumn Tree Color by
Updated April 21, 2017
University of Georgia silvics professor, Dr. Kim Coder, suggests there are ways to predict how beautiful a fall color and autumn leaf display will be. Key predictors are used along with a good mix of common sense and can forecast the quality of a viewing season with surprising accuracy.
The fall season should start with substantial leaf volume. The more leaves attached to trees entering the color season means more to look at. Droughty summer weather conditions can limit that volume but a wet summer can set up disease and insects. You hope for a moderately dry summer. Health
Healthy leaves not only present quality viewable leaf surfaces to look at but vigorous leaves stay attached to trees longer. Pest and environmental problems can damage and disrupt leaf surfaces so much that they can actually detract from a quality viewing season. Increased pests can be a factor of both weather and temperature during the summer growing season.
Temperature and Precipitation
Cool night temperatures with no freezes or frosts and cool, bright, unclouded sunny days will enhance the leaf color change. Slightly dry conditions in the last half of the growing season and on into the fall have a positive effect.
Here are the conditions Dr. Coder says contribute to a poor season:
"Fall rain fronts and long overcast periods diminish color presentation. So do strong wind storms that blow the leaves from the trees. Wet and humid growing seasons lead to many leaf infections and premature leaf abscission. Freezing temperature and hard frosts stop color formation dead."
A true leaf-peeper will keep accurate annual records of peak color days over the past decade. Peak color day dates tend to repeat themselves over time.
Home Science Tools Improved Learning: LEAF CHROMATOGRAPHY EXPERIMENT Leaves contain different pigments, which give them their color. Green chlorophyll is the most common type of pigment, but there are also carotenoids (yellow, orange) and anthocyanins (red). Chlorophyll, which is essential for photosynthesis, usually hides the other pigments, except when autumn comes along and it begins to break down. This is why leaves turn different colors in the fall.
Do this project to see the hidden colors in a green leaf and predict what color it will be in the fall! (Adult supervision recommended.)
What You Need:
Green leaves from several different trees (Trees with a dramatic color change, like maples, work best)
Beaker or drinking glass
Isopropyl (rubbing) alcohol
Chromatography or filter paper (you can use coffee filters)
What You Do:
Keep leaves from different trees separate and follow the steps below for each set of leaves, so you can compare results.
Tear the leaves into several pieces and place them in a beaker or glass, then add just enough rubbing alcohol to cover them. Cover the beaker with plastic wrap to keep the alcohol from evaporating.
Put the beaker in a dish of hot tap water for about 30 minutes, until the alcohol turns green as the pigments from the leaves are absorbed into it.
Cut a strip of filter paper about a half inch wide and tape it to a pencil. Suspend the pencil across the beaker and let the strip just barely touch the alcohol and pigment mixture.
A bit of the mixture will travel slowly up the paper. After about 30-90 minutes you should be able to see the “green” color break up into several different colors as the different pigments begin to separate. You’ll see different shades of green, and perhaps other colors as well. Which leaves had the most colorful pigments? Based on your experiment, which trees’ leaves do you think will turn the brightest and least brightest colors this fall?