|Back to Back Issues Page|
Why leaves Change Colors
October 19, 2015
Growing season is officially over in southwest Michigan.
We woke to a hard frost and freezing Sunday morning.
Still, we were blessed with a later than normal growing season.
There are enough green tomatoes for a couple batches of green fried maters.
Another mess or two of pepper poppers as well.
I've been cutting back perennials so I'm not totally overwhelmed.
Now comes the task of cutting and pulling all of the annuals.
This is always a somber time for me as the landscape is barren, or seems so.
Lord willing, I have next growing season to plan and prepare for over the next few months.
When cutting back and pulling out plants remember this
Any plants or foliage that are sick or diseased need to be bagged and put into the trash, landfill, etc.
By leaving them to decompose in your gardens and flowerbeds, you are spreading the sickness.
Same goes for compost piles, they don't get hot enough to kill off everything.
Any mildew, blackspot, rust.
Any form of wilt, or scab.
All foliage and plant parts must be removed.
This isn't a guarantee you will be trouble free next year.
It simply give you a leg up on the problems that will occur.
Fungus winter over.
Viruses like Verticillium wilt and Apple Scab are there for the duration.
You can pretty much prevent fungus from reappearing.
Viruses like apple scab, you must treat to keep them under control.
Verticillium wilt, you will need to plant elsewhere next year.
I can get long winded at times, however if I can help just one gardener, then I have done my job.
Fall colors are 10 - 14 days behind a normal Autumn.
Normally we have hit peak colors around here, we still have some time to go.
Oh, there are a few trees that are simply breathtaking, but the landscape at a whole is a bit off.
Our late spring has a lot to do with this.
I have been asked by a couple of readers on why leaves change colors.
This is a topic I write on every few years, we are due.
For some of you, this will be a refresher course.
Still for others, you are going into a new world of Creator/science.
Yes, you can't have one without the other.
It starts with a whisper.
A lonely leaf.
Maybe a single branch.
Possibly a lone tree along the street or in a field.
Slowly a crescendo of colors builds to a fiery pitch, where the hills and valleys scream out.
Look At Me........
Here I am..........
Come, and enjoy Nature's show.
Timing can be everything.
It doesn't last.
"A Touch of the Master's Hand".
In awe and cognizant of His presence.
Still, Timing is Key.
Hop in the car or go for a walk.
Take a road trip or make it a long weekend.
Catch the show before it passes for the year.
Days continue to grow shorter and cooler.
Gardens are pretty well done growing for most of us.
Like the Grand Finally of a fireworks display, Nature offers us one last hurrah.
A Grand Finally before she goes to sleep for the winter.
The end of another wonderful growing season.
A reminder to us all, that God is indeed in control.
(You don't think all of these wonderful orchestrated events just happens do you?)
For years, scientists have worked to understand the changes that happen to trees and shrubs in the autumn.
Although all the details aren't known, there is enough knowledge and know how to explain the basics and help you to enjoy more fully ' Nature's ' multicolored, autumn farewell.
Three factors influence autumn leaf color.
Leaf pigments, length of night, and weather, but not quite in the way we think.
The timing of color change and leaf fall are primarily regulated by the calendar, that is, the increasing length of night.
Length of day is the one constant year after year.
None of the other environmental influences ...........
Temperature, rainfall, food supply, and so on, are as unvarying from year to year.
As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Autumn's palette.
Why Do Leaves Change?
Leaves are nature's food factories.
Plants take water and oxygen from the ground through their roots.
They take a gas called carbon dioxide from the air.
Plants then use sunlight to turn water and carbon dioxide into glucose.
Plants use glucose ( a kind of sugar) as food for energy and as a building block for growing.
The way plants turn water and carbon dioxide into sugar is called 'Photosynthesis'.
That 'word' we all learned about at one time or another.
It means 'putting together with light.'
A chemical called chlorophyll helps make 'Photosynthesis' happen.
You all know that chlorophyll is what gives plants their green color.
Where do the Autumn Colors Come From?
A color palette needs pigments, and there are three types that are involved in Autumn color.
The quiet green of summer foliage is transformed into the vivid autumn reds, oranges, yellows, golds, and browns before the leaves fall off the trees.
On years like this one, the colors are truly breathtaking.
Chlorophyll, which gives leaves their basic green color.
It is necessary for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture sugars for their food.
Trees in the temperate zones store these sugars for their winter dormant period.
Carotenoids, which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.
Anthocyanins, which give color to such familiar things as cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums.
They are water soluble and appear in the watery liquid of leaf cells.
Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season.
Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.
During the growing season, chlorophyll is continually being produced and broken down and leaves appear green.
Phosphate is at a high level.
Phosphate has a vital role in the breakdown of the sugars manufactured by chlorophyll.
But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant.
When this happens, the sugar-breakdown process changes, leading to the production of anthocyanin pigments.
As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed.
The brighter the light (more sunny days) during this period, the greater the production of anthocyanins and the more brilliant the resulting color display that we see.
When the days of autumn are bright and cool, and the nights are chilly but not freezing, the brightest colorations usually develop.
The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.
The carotenoids occur, along with the chlorophyll pigments, in tiny structures called 'plastids' within the cells of leaves.
Sometimes they are in such abundance in the leaf that they give a plant a yellow-green color, even during the summer.
But usually we become aware of their presence for the first time in autumn, when the leaves begin to lose their chlorophyll.
Certain colors are characteristic of particular species.
Oaks turn red, brown, or russet;
Hickories turn golden bronze;
Ash species (those that are still alive) turn yellow or purple.
Aspen and yellow-poplar, are a golden yellow.
Dogwood turn purplish red;
Beech, light tan.
Sourwood and black Tupelo turn crimson.
Maples differ species by species-red maple turns brilliant scarlet.
Sugar maple, orange-red; and black maple, glowing yellow.
Striped maple becomes almost colorless.
Leaves of some species such as the elms simply shrivel up and fall, exhibiting little color other than drab brown.
Are you getting them idea here?
The timing of the color change also varies by species.
Sourwood in southern forests can become vividly colorful in late summer while all other species are still vigorously green.
Oaks put on their colors long after other species have already shed their leaves.
These differences in timing among species seem to be genetically inherited.
For a particular species at the same latitude will show the same coloration in the cool temperatures of high mountain elevations at about the same time as it does in warmer lowlands.
How does weather affect autumn color?
The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is dwindling.
The best places in the world for viewing fall colors is probably the Eastern United States and Michigan's Upper Peninsula.
This is because of the climate there, and the wide variety of deciduous trees.
The brightest colors are seen when late summer is dry, and autumn has bright sunny days and cool (low 40's Fahrenheit) nights.
Then trees make a lot of anthocyanin pigments.
A fall with cloudy days and warm nights brings drab colors. And an early frost quickly ends the colorful display.
Temperature and moisture are the main influences.
A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays.
During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out.
These conditions offer lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson.
Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.
The amount of moisture in the soil also affects autumn colors.
Like the weather, soil moisture varies greatly from year to year.
The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike.
A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks.
A warm period during fall can also lower the intensity of autumn colors.
A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.
What triggers leaf fall?
In early autumn, in response to the shortening days and declining intensity of sunlight, leaves begin the processes leading up to their fall.
In late summer the veins that carry fluids into and out of the leaf are gradually closed off as a layer of special cork cells forms at the base of each leaf.
As this cork layer develops, water and mineral intake into the leaf is reduced, slowly at first, and then more rapidly.
It is during this time that the chlorophyll begins to decrease.
Often the veins will still be green after the tissues between them have almost completely change color.
These clogged veins trap sugars in the leaf and promote production of anthocyanins.
Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.
What does all this do for the tree?
Winter is a certainty that all vegetation in the temperate zones must face each year.
Perennial plants, including trees, must have some sort of protection to survive freezing temperatures and other harsh wintertime influences.
Stems, twigs, and buds are equipped to survive extreme cold so that they can reawaken when spring heralds the start of another growing season.
Tender leaf tissues, however, would freeze in winter, so plants must either toughen up and protect their leaves or dispose of them.
Plant native or zone hardy.
I'm sure you got more than you bargained for today.
In God's work you will find science.
After all, he is the great scientist, the Great Creator.
Well, it's time to fly for now.
Before I go, here is your positive thought for the day.
“Patience is waiting.
Not passively waiting.
That is laziness.
But to keep going when the going is hard and slow
- that is patience.”
The Holy word teaches on patience.
Here is a sampling.
Be completely humble and gentle;
Whoever is patient has great understanding,
Be joyful in hope, patient in affliction, faithful in prayer.
"Treat the earth well:
It was not given to you by your parents,
It was loaned to you by your children.
We do not inherit the Earth from our
Ancestors, we borrow it from our Children."
Ancient Indian Proverb
Your friend indeed,
Better yet, have them sign up so they can receive their own letters.
|Back to Back Issues Page|