Posted on 09/30/2023 5:32:13 AM PDT by Diana in Wisconsin
The Science of Fall Colors
For years, scientists have worked to understand the changes that occur in trees and shrubs during autumn. Although we don’t know all the details, we do know enough to explain the basics to help you enjoy nature’s multicolored display. Three factors influence autumn leaf color:
leaf pigments
length of night
weather
The timing of color changes and the onset of falling leaves is primarily regulated by the calendar as nights become longer. None of the other environmental influences – such as temperature, rainfall, food supply – are as unvarying as the steadily increasing length of night during autumn. As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Nature’s autumn palette.
Leaf Pigments
A color palette needs pigments, and there are three types that are involved in autumn color:
Carotenoids: Produces yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.
Anthocyanin: Gives 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.
Chlorophyll: Gives leaves a basic green color. It is necessary for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture sugars for food.
Trees in the temperate zones store these sugars for the winter dormant period.
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. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanin that are present in the leaf are then unmasked and show their colors.
Certain colors are characteristic of particular species:
Oaks: red, brown, or russet
Hickories: golden bronze
Aspen and yellow-poplar: golden yellow
Dogwood: purplish red
Beech: light tan
Sourwood and black tupelo: crimson
The color of maples leaves differ species by species:
Red maple: brilliant scarlet
Sugar maple: orange-red
Black maple: glowing yellow
Striped maple: almost colorless
Some leaves of some species, such as the elms simply shrivel up and fall, exhibiting little color other than drab brown.
The timing of the color change also varies by species. For example, 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.
Length of Night
In early autumn, in response to the shortening days and declining intensity of sunlight, leaves begin the processes leading up to their fall. The veins that carry fluids into and out of the leaf gradually close off as a layer of cells forms at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanin. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.
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. 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 – lots of sugar and 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 will 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.
Continues at link: https://www.fs.usda.gov/visit/fall-colors/science-of-fall-colors
Hey lady. We are just starting to see a few leaves turn here in west Michigan. Yanking plants in the garden today. Fall raspberries have been plentiful. Making some preserves today.
Been cleaning out garden beds, myself. Looks like a nice weekend for more of that. Otherwise, dealing with my ABUNDANCE of apples this season. More pies and pie filling are in the works for the weekend. Apple sauce, butters and jams are all done! :)
Beau will be back from Bear Camp on Monday, so I have kennels to prep for the dogs’ return and I’ll TRY to get some housework done before they all get back, but I’m not making any promises. ;)
I finally got the last of the storage crops dealt with. Spuds are in the root cellar. Tomatoes are ripening on shelves under lights and being processed into marinara, juice, or dried. Of course we are enjoying BLT’s with the ripe tomatoes and home cured and smoked bacon. Carrots and cabbages are in big coolers going out on the deck in the day and in the house at night while the root cellar cools down. It won’t be long, it is about 42 down there. The green beans are canned up, and the peas are in the freezer. It is running around 25 in the mornings. I got all the dahlia and lily bulbs out of the pots and am waiting for them to dry a bit before storing them in the root cellar. The wheel of seasons keeps turning no matter what else happens. Comforting, that.
“The wheel of seasons keeps turning no matter what else happens. Comforting, that.”
I love that! :)
Sounds like you’re all set for the winter. Jealous of your home-cured bacon! We are getting 1/2 a hog raised by a neighbor this month. Can’t wait! :)
Our maples around the driveway are starting to turn.
Company coming tomorrow - big bathroom project 95% done (all the hard stuff). Grass will get mowed this afternoon - picked up Ophelia debris yesterday afternoon & so did mom, got a trailer full - lots of small branches down.
I won’t be able to get in the garden to repair the landscape fabric damaged by the stray horses & work on clearing out the beds until Monday. Another relative wanted to visit Wednesday, but mom will be out of town. There is a possibility this cousin can change their schedule & come either Tuesday or Thursday. I really want to get the garden squared away.
Weather is supposed to be beautiful this week, then not so good over the next weekend again (we have another trip planned over that weekend).
At the moment, trying to figure out how to store my canned goods in an orderly fashion that makes sense - everything is on the fireplace hearth & the dining room table!
My beautiful Silk Floss tree has started to bloom, the flowers look like orchids:
Also, the roses are making their fall comeback, blooms are always much smaller in the fall.
Deserves a rest after catching three more tree rats this week:
Just starting here in the Boston Area.
Good morning...looks like we will have a glorius Fall week. Got rain this past week. Found a fat Armenian Cuke among the vines I was ripping out. Grey diggers missed one!
The trees are just beginning to change here in NH.
It’s been wetter than wet so unlike the last few years where it was so dry the leaves just turned brown before they fell, we should have a good show.
The trees are just beginning to change here in NH.
It’s been wetter than wet so unlike the last few years where it was so dry the leaves just turned brown before they fell, we should have a good show.
Sorry for the double post.
My son also told me about this guy and his forecast for the upcoming winter.
It’s a 9 minute video but explains the weather forecast for this winter well and why he thinks it’s going to be milder and snowier than usual in the east.
Here’s When You’ll See Snow This Year…
https://www.youtube.com/watch?v=Ndp8nrMQq3o
We are supposed to get snow this weekend.
“At the moment, trying to figure out how to store my canned goods in an orderly fashion that makes sense - everything is on the fireplace hearth & the dining room table!”
That’s on my ‘To-Do’ list too, but it includes emptying out the ENTIRE Pantry under the steps..and I’m just not willing to do that yet! It always takes a special kind of motivation - usually colder weather - to talk me into it. ;)
Mid-to-low 80’s for a week, then rain then 60’s and 50’s, which I LOVE. :)
Making good progress on cleaning out garden beds - lots of flowers still going strong and the Dahlias are leading the pack. SO GORGEOUS this season. Must be the ‘Ithaca Grow’ that went into the beds this spring. ;)
That is one efficient killing machine you’ve got there. Good Kitty!
It’s always best to leave the housework for last. This strategy has worked well for me. But then I live alone . . .
https://www.cbsnews.com/boston/weather/
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