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.
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.
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:
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!
Lifts a concrete block(40 lbs) with very little strain.
Lifts two concrete blocks with considerable strain, too much imho.
All but the gearmotor and $15 of hardware/cable is stuff I grabbed from the scrap pile at work. None of it accept the gearmotor is permanent but it lets me know that my guess-timations for power/dimensions/speed etc are all good to go and the motor will work. My limit for EMT conduit that will be the frames for the drop down sides is 3/4" which will weigh 36.8 lbs. Call it 40 lbs with plastic film and hardware. One inch EMT would be 53.6 lbs plus and would probably work but I'd rather not load the motor any more than I need to.
An observation I had is that the gearmotor spins a little after power is cut off and it pulls another 1/2" to 3/4" of cable in. I'm going to have a limit switch to cut power when the side is all the way closed. Rather than try to time things just right for that 1/2" to 3/4" run-on, I'll add an extension spring to the cable.
$25 per gearmotor plus cable, different spool/drum setup, springs and bearings and I'll have about $350 into the sides when all's said and done. Motorized and automated.
Got a question…..
My Brussel Sprouts have not yet got sprouts. NOTHING on any of them.
What could be causing that?
I do have them covered with netting to keep those danged butterflies off them or the caterpillars decimate, and worse, the crop, but other than that, I can’t think of anything else.
It has been a very wet year, too.
FWIW, my bucket potato crop is fantastic. The onions did not do well and probably won’t store well, but the garlic and potatoes did great.