Graphical Headline Archive pick
September 23, 2002
The Time of the Seasons
Did you feel it this morning — the way the air was crisp and cool, not hot and humid? Or did you notice that the color of the leaves on the trees has really started to change? Or maybe you saw another large, V-shaped flock of Canadian geese flying overhead, off on its journey south. It doesn't take a rocket scientist or a meteorologist to know what's going on. Fall is finally here.

The official autumnal equinox occurred earlier today, September 23, at 12:55 a.m. This marks the official beginning of fall in the Northern Hemisphere. (If you were living in the Southern Hemisphere, today would be the vernal equinox and would mark the beginning of your spring!) On the equinox, there are 12 hours of daylight and 12 hours of night at all locations on Earth. The word equinox means "equal night."

From now until the winter solstice on December 21, the days get will shorter. Temperatures will drop because the Northern Hemisphere is tilted away from the Sun, and thereby receives less of its solar energy.

The Fall Palette
In many places in the United States, the changing colors of the leaves marks the visible arrival of fall. This transformation is a phase in the process of photosynthesis. In photosynthesis, plants use water and carbon dioxide to produce oxygen and sugars. Photosynthesis takes place inside specialized plant cells called chloroplasts and enables plants to build new tissue for growth.

Sunlight must be present in order for photosynthesis to occur. As the days get shorter and the amount of sunlight is reduced, the chloroplasts in the leaves gradually shut down the food-making operation. As a result, chlorophyll, the pigment that gives green plants their color, begins to disappear from the leaves, making way for yellows, oranges, and browns. These more colorful pigments — orange carotene and yellow xanthophyll — are always present in leaves but aren't visible in the summer because of the abundance of green chlorophyll. Brighter oranges and fiery reds are found in the leaves of trees that are able to take carbohydrates out of the leaves and turn them into red pigments called anthcyanins.

The best conditions for producing colorful fall foliage are clear days followed by cool nights. Too much rain, or early frosts and freezing temperatures, diminish the colors. Too little rain can kill the leaves before they even have a chance to change color; instead of yellows and reds, the leaves quickly turn brown. However, "leaf peepers" and other experts generally agree that it is a combination of variables that produces vibrant fall colors.

Fall is everywhere. From the Northeast to the Plains, landscapes come to life with autumn's brilliant colors. Even coastal salt marsh grasses change color from green to golden in autumn. Mid-September to the beginning of November marks the best time to see this annual autumn phenomenon, depending on where you live, weather, and other conditions. But weather forecasters and amateur tree specialists alike admit that predicting peak viewing time is not an exact science.

In New England, viewing fall foliage is an $8 billion business. About 400,000 tourists travel to Maine annually just to see the spectacular scenery. So it's no surprise that Vermont and other New England states have fall foliage "hot lines" and Web sites where potential tourists can track the trees' changing colors on maps or see the color status on live Web cams. The U.S. Department of Agriculture has its own Fall Color Hotline and Web page with links to regional sites around the country.

Be A Leaf Peeper
If you live in New England, you already have the fall spectacular right in your backyard. However, if you and your family are looking for a weekend road trip to see more of fall's finery, check out the site from Yankee Magazine. While you're there, check out the nifty Leaf Identification Chart, which shows leaf names, shapes, and what colors they change to and when.

Some say the best way to preserve the fall colors is with a camera or a set of watercolors. But if you want to save the actual leaves themselves, you can. Read how in this article by Marianne Ophardt.

Sunscreen for Trees
Researchers at the University of Wisconsin-Madison announced a theory in 2001 that the red pigments — the anthocyanins — in trees such as maples and oaks act as a natural sunscreen, protecting the leaves from sunlight while the tree reabsorbs nutrients from the leaves. Read more about the theory at Science Daily.

Getting Ready for Winter
It isn't only the trees that prepare for winter. Animals such as woodchucks eat throughout the fall in a deliberate effort to gain weight. The extra weight and stored fat help the animals survive hibernation. A "true hibernator," the woodchuck remains dormant all winter and emerges, thin and hungry, in March.

Chipmunks and squirrels collect nuts and seeds throughout the fall, then stash them underground. These rodents are "winter sleepers," meaning they don't hibernate completely, but will sleep for long periods and wake on occasion to eat from their buried food supplies.

Dwindling food supplies cause birds to migrate to warmer climates in fall. According to some estimates, more than 5 billion birds migrate across North America every autumn. As the days shorten, hormonal changes signal the birds to prepare for their journey south. Birds also accumulate fat, which they use during migration when they fly for long uninterrupted periods.

Of course, people also start our winter preparations in fall. Chilly fall days call for sweaters, scarves, and gloves. Fall is a good time to check heating, electrical, and plumbing systems, clean fireplaces, stock wood for wood-burning stoves, and check heating oil supplies. But don't be in too much of a hurry for winter to get here. You don't want to miss apple pies, jumping in leaf piles, or Halloween.

The Language of Fall
Poets and writers often find inspiration in nature and the seasons. Autumn is no exception, though it sometimes seems the creative mind is more susceptible to negative images of what autumn means. Take D.H. Lawrence, for example. He wrote, "The autumn always gets me badly, as it breaks into colours. I want to go south, where there is no autumn, where the cold doesn't crouch over one like a snow leopard. The heart of the North is dead, and the fingers are corpse fingers."

Luckily, not all writers are quite so depressed by autumn as Lawrence! Read the following poems about fall and think about the poets' different reactions to this season of transition.

My November Guest
by Robert Frost

My Sorrow, when she's here with me,
Thinks these dark days of autumn rain
Are beautiful as days can be;
She loves the bare, the withered tree;
She walks the sodden pasture lane.

Her pleasure will not let me stay.
She talks and I am fain to list:
She's glad the birds are gone away,
She's glad her simple worsted grey
Is silver now with clinging mist.

The desolate deserted trees,
The faded earth, the heavy sky,
The beauties she so truly sees,
She thinks I have no eye for these,
And vexes me for reason why.

  • How do you think the speaker feels about autumn? Which words does the poet use to help convey the speaker's feelings?
  • Why will Sorrow's "pleasure not let me stay?"
  • Reread the last two lines of the poem. Why does Sorrow "vex" the speaker?

October's Party
by George Cooper

October gave a party;
The leaves by hundreds came-
The Chestnuts, Oaks, and Maples,
And leaves of every name.
The Sunshine spread a carpet,
And everything was grand,
Miss Weather led the dancing,
Professor Wind the band.

The Chestnuts came in yellow,
The Oaks in crimson dressed;
The lovely Misses Maple
In scarlet looked their best;
All balanced to their partners,
And gaily fluttered by;
The sight was like a rainbow
New fallen from the sky.

  • How does the poet bring October to life?
  • Which words or phrases provide clues as to the poet's feelings about October? How would you describe the mood of this poem?
  • Why do you think "Chestnuts, Oaks, and Maples" are written with initial capital letters?
  • How does the mood of this poem compare with the Frost poem?

How does autumn make you feel? For a fun, creative activity, consider keeping a special fall journal where you can jot down all of the changes you see over the next few weeks. Write down which trees changed colors first. What colors did you see and where? How quickly did the leaves change? Add drawings of leaves or descriptions of the weather, what the local wildlife is up to, the first house to decorate for Halloween, etc. Think of descriptive words and phrases and write your own autumn poem. Be creative! And have a great fall!

Related Activities
Overview of Photosynthesis
Learn more about leaves in this Middle School Science Gateways activity.
Photosynthesis & Plant...
Take an Internet field trip to discover why leaves change color.
The Monarch Migration
This is also the time of year for monarch butterflies to migrate to Mexico.