WORLD Radio - Autumn aesthetics
What’s behind the season’s changing colors?
NICK EICHER, HOST: Today is Tuesday, September 28th. Thank you for turning to WORLD Radio to help start your day.
Good morning. I’m Nick Eicher.
MARY REICHARD, HOST: And I’m Mary Reichard. Coming next on The World and Everything in It: it’s fall!
Last week marked the official start of autumn: for many of us that means it’s time to get out the sweaters, attend high school or college football games, and perhaps visit an apple orchard or pumpkin patch.
EICHER: Reporter Lillian Hamman stopped by a North Carolina orchard this weekend and found some real enthusiasm for autumn.
MONTAGE: WHAT DO YOU LIKE ABOUT FALL?
And of course nearly everyone mentioned fall colors—when the leaves change from green to bright yellow, red, and orange. WORLD’s Paul Butler caught up with a botanist to help us understand what’s going on to make this time of year as beautiful as it is.
PAUL BUTLER, REPORTER: According to the 2021 Fall Foliage Map, this week marks peak color across the northernmost states as well as in the higher elevations of the Rocky and Appalachian Mountains. But in less than a month's time, most of the country will be ablaze in yellows, oranges, reds, and a whole range of golden browns. This time of year, even Crayola has a difficult time keeping up.
PARIS: I'm Bob Paris, and I'm an associate professor at Cedarville University. I teach biology...
For most of the year, leaves kind of blend into the background. We don’t usually think much about them. But as Bob Paris points out, they’re a crucial part of our ecosystem.
PARIS: Well, a leaf is...we could think of it as a very highly technical solar panel. So the leaf is going to be the site where the plant converts sunlight into energy that the plant can use. And it does that by taking air, water and sunlight and makes sugar...producing energy not only for the plant, but really for most of life on the planet...
As you may remember from junior high science class, throughout the spring and summer, chlorophyll is the predominant pigment in the leaf. It makes photosynthesis possible and it’s what makes leaves bright green. But, there are usually other pigments also present—we just can’t see them due to the amount of chlorophyll.
PARIS: So as we approach this time of year in the fall, the natural process...start to disassemble those chlorophyll molecules as the chlorophyll decreases in the leaf, then we start to see some of those background colors pop out.
Those other pigments include carotenoids [carrot-noids] and xanthophylls [zanth-a-phills] —which we perceive as oranges and yellows. So as the days get shorter, and the sun less intense, the green chlorophyll begins to break down, and the background pigments reveal themselves.
But some leaves are designed with a very a different chemical process:
PARIS: There are also a few other compounds that begin to be manufactured in the fall. And that would be some of the anthocyanins compounds that would cause the leaves to have a red or maybe more of a purplish color. And those are being manufactured at this time of year.
However the leaves change color, at the Skytop Orchard, in Flatrock, North Carolina, there are many opinions on which fall colors are the best, as Lilian Hamman found out:
As for Bob Paris, he’s got a definite favorite too:
PARIS: Oh, yeah, do I really, I really enjoy the sugar maple and...certain trees are marked more colorful than others, but it tends to have a really bright kind of, almost fiery orange, red color to it. And on a sunny day just against the blue sky, it's a pretty, pretty amazing picture. So that's probably my favorite.
The intensity of fall colors is directly related to the weather conditions throughout the year, not just in the autumn.
PARIS: So probably the biggest factor is moisture. We need plenty of moisture to keep the leaves growing and healthy and, and productive so that they kind of go through what we would consider a normal fall decline in their in their growth.
Areas experiencing drought may still have colorful displays, but the leaves usually turn earlier than usual, and inconsistently. And the leaves drop much faster as well: All signs that the trees and plants are under stress.
If the fall is particularly wet, and without a lot of sunshine, the colors will be muted.
PARIS: We also need sunlight to kind of keep them growing...So typically in the fall, as well in the summer, we need nice, even rainfall—and then in the fall we like to have cool nights with bright sunny days and that helps kind of push the leaves along their normal route which then results in all of these vibrant colors we see.
Of course one major downside to the beautiful fall display is when that color moves from the trees...to the ground. Paris encourages people to look differently at this valuable natural resource. Don’t burn them, or bag them up. Compost them if you can.
PARIS: Composting really, I think, can become a valuable way to do that because it provides a nutrient rich media in the spring for gardening. So it's kind of a win win situation we can use it for for weed control, we can use it for sort of a organic fertilizer application.
And if you don’t have room to compost, then Paris says the next best thing is to get the mower out, mulch them into small pieces, and let them fertilize your lawn and garden.
PARIS: Of course you don't want to concentrate all of those leaf clippings in one spot but if they're spread out, they can be a very helpful source of nutrients. So really my favorite way to to handle it is the compost and really, it kind of saves you in the spring from having to purchase other inputs that you might normally have for your garden.
Reporting for WORLD, I’m Paul Butler.
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