- Why do leaves change color in the fall season?
- When and where fall foliage colors will peak, in one map
- This Map Reveals When Fall Colors Will Peak Across the U.S. This Year
- Here’s The Scientific Reason Why Leaves Change Color In The Fall
- We marvel the world over at this beautiful yearly phenomenon, but why it happens in the first place is not so pretty.
- Photosynthesis Makes For Green Leaves
- Why Leaves Change Color
- Red Leaves Particular To Fall
- Why More Autumn Leaves Are Red In America And Yellow In Europe: New Theory
- The science behind why leaves change color in autumn
- What Month Do Leaves Change Color and Fall Off Trees?
- Fall Foliage Forecast (Northeast, Midwest, South, and West)
- How do trees change in the fall?
- What do they do have in common?
Why do leaves change color in the fall season?
In some areas of the world, the weather changes in the fall, making the air turn cold. During this time, many leaves also change colors. Why does this happen?
Deciduous trees drop their leaves in winter. Image by Paul Buckingham.
First let’s think about why some trees drop their leaves before winter. In the winter, it would take a lot of energy and water for plants to keep their leaves healthy. But winter is cold, dry, and usually there isn’t much sun (which helps give plants energy). So, instead of trying to keep their leaves, some plants drop their leaves and seal the spots on their branches where the leaves had been attached.
How is this related to what makes leaves colorful?
Leaves are colored by molecules called pigments. The pigment that causes leaves to be green is chlorophyll. Chlorophyll is important for plants to make food using sunlight. During spring and summer when there is plenty of sunlight, plants make a lot of chlorophyll.
In autumn when it starts to get cold, some plants stop making chlorophyll. Instead, those plants break down chlorophyll into smaller molecules. As chlorophyll goes away, other pigments start to show their colors. This is why leaves turn yellow or red in fall.
In fall, plants break down and reabsorb chlorophyll, letting the colors of other pigments show through. Image by Sander van der Wel.
The color change usually happens before the leaves fall off of the tree. Why might that be? It takes a lot of energy to make chlorophyll. If the plants break down the chlorophyll and move it out of their leaves before the leaves fall, plants save energy. The plants can reabsorb the molecules that make up chlorophyll. Then, when it’s warm and sunny enough to grow again, the plants can use those molecules to remake the chlorophyll. That way the plants don’t have to make chlorophyll from scratch.
There are other pigments in leaves called carotenoids. Carotenoids are yellow and orange. Anthocyanins are other plant pigments that are only made in the fall. These pigments cause red, pink, or purple colors. Anthocyanins also protect leaves from being eaten or getting sun burned.
So the different colors in leaves are caused by changes in the pigments. When the weather changes, some plants break down all the green pigment. This lets beautiful yellows, oranges, and reds come through in the fall.
To learn more about how plants grow, try this link.
- Snacking on Sunlight
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.
When and where fall foliage colors will peak, in one map
Labor Day is nearing, pumpkin spice is about to be pumped into countless hot beverages (and, for the first time, into Spam?!), and some grocery store shelves are already being stocked with Halloween candy. The autumn season brings many changes, but none are more spectacular than this: Billions of leaves will turn from green to auburn and gold.
When days begin to grow shorter, deciduous (green leafy) trees start signaling their leaves to stop producing chlorophyll, the green pigment responsible for the leaves’ color and photosynthesis.
Because the color change is more dependent on light than temperature, it takes place at basically the same time year after year, according to the US National Arboretum.
Temperature and weather conditions, though, can impact the intensity of fall colors and how long they linger. They can also subtly affect the timing of when the leaves start to change. And drought can change the rate at which the leaves turn.
Because of all the variables at play, it can be tough to predict precisely when fall colors will peak, and how long they’ll last, in a particular area. But here’s an admirable effort:
The website SmokyMountains.com (a site promoting Smoky Mountains tourism) created this interactive map to determine peak fall colors across the United States by county. You can slide the bar at the bottom of the map to see how the peak foliage spreads out across the country over the coming weeks. Use it to figure out the right time to do some leaf-peeping in your area or on a weekend trip.
The map pulls historical data and seasonal forecast predictions from the National Oceanic and Atmospheric Administration and makes a best guess about peak timing. “Although the scientific concept of how leaves change colors is fairly simple, predicting the precise moment the event will occur is extremely challenging,” Wes Melton, the chief technology officer of SmokyMountains.com, says in a press statement. So the predictions may not be 100 percent accurate. (Here’s another easy way to figure out whether the map is accurate for your home: Go outside!)
Why do the leaves turn red, orange, or yellow?
When the chlorophyll disappears from the leaves, the National Arboretum explains, other chemicals persist and show their colors:
Chlorophyll normally masks the yellow pigments known as xanthophylls and the orange pigments called carotenoids — both then become visible when the green chlorophyll is gone. These colors are present in the leaf throughout the growing season. Red and purple pigments come from anthocyanins. In the fall anthocyanins are manufactured from the sugars that are trapped in the leaf. In most plants anthocyanins are typically not present during the growing season.
Different trees will reveal different colors, as the US Forest Service describes on its website. The leaves of oak trees, for example, turn reddish brown or russet. Here are a few others:
– 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
This Map Reveals When Fall Colors Will Peak Across the U.S. This Year
No one wants to be the bearer of bad news, but summer is coming to a close. Sorry. Ritualistic discussion of the return of pumpkin-spice as though it’s a prophesized diety has already started. Halloween and back to school talk has infiltrated the planning of beach weekends over your favorite or most-tolerated hard seltzer.
Fortunately, autumn has its own charms, not least of which is fall foliage. Peak leaf-peeping season is coming, albeit a little later than usual. SmokyMountains.com has released its annual interactive fall foliage forecast map, predicting when and where leaves are going to be at their prime. Yes, it’s time to start planning your apple cider-rich drives through the leafy parts of the state.
Of course, there are a lot of factors impacting when leaves hit their peak, so no map projecting the changing of colors is going to be 100% accurate. A warm spell or a storm that strips the trees of their leaves is going to change the projections. Nonetheless, at the moment, these are the best projections available based on a number of factors, including peak observation trends, the National Oceanic and Atmospheric Administration (NOAA) historical temperatures, NOAA historical precipitation, NOAA forecast temperatures, NOAA forecast precipitation, and historical leaf peak trends.
“The predictive fall leaf map helps potential travelers, photographers, and leaf peepers determine the precise future date that the leaves will peak in each area of the continental United States,” said data scientist and SmokyMountains.com CTO Wes Melton. “By utilizing the date selector at the bottom of the map, the user can visually understand how fall will progress over a region.”
Here’s The Scientific Reason Why Leaves Change Color In The Fall
We marvel the world over at this beautiful yearly phenomenon, but why it happens in the first place is not so pretty.
With the autumn season comes the gorgeous display of fall foliage. After the summer heat subsides, trees transform from a luscious green into a fiery display of red, orange, and yellow hues. The color-changing process is simply magical. But as with most phenomena in the world, there is a thorough scientific explanation of this magic, and consequently as to why leaves change color in the fall.
While the leaves in their autumn hues are beautiful, the reason behind their transformation is anything but. We are, in essence, watching the leaves starve themselves and die.
But first, to understand why leaves change colors come fall, it’s important to understand why they’re green in the first place.
Photosynthesis Makes For Green Leaves
At one point or another, you’ve probably learned about the process of photosynthesis. If not, here’s a short explanation.
Photosynthesis, in plain English, means “putting together with light,” and that’s because plants literally put two ingredients together with sunlight in order to make the food it needs to survive.
Plants need three things to keep them alive — water, carbon dioxide, and sunlight. Water is absorbed by a tree or plant through its roots. Carbon dioxide is absorbed via tiny holes in plant’s leaves, flowers, branches, stems, as well as its roots.
Sunlight is absorbed by a chemical in the tree’s leaves known as chlorophyll. Chlorophyll absorbs red and blue light, which is why it looks green.
Once the sunlight has been absorbed, it reacts with the water and carbon dioxide that was also absorbed in order to produce sugars, which is essentially plant food. Those sugars are then transported throughout the plant as fuel.
Because chlorophyll needs sunlight and warmth in order for a plant to produce it, chlorophyll production begins to deteriorate when the colder months set in — and this is why leaves change color come fall.
Why Leaves Change Color
In addition to the green pigments of chlorophyll, a plant’s leaves also have yellow and orange pigments in them all the time. Yellow and orange colors are due to pigments called carotenoids, which are also responsible for the color in carrots and in corn.
But most of the year these other, warmer, colors are masked by the great amounts of chlorophyll in the plant. When temperatures begin to drop and chlorophyll production begins to decline, those other colors are revealed.
“The color of a leaf is subtractive, like crayons on a piece of paper,” David Lee, who has studied leaf color since 1973, explains of why leaves change color.
Red Leaves Particular To Fall
When leaves change color, another pigment becomes visible: flavonoids, which are responsible for the reds. These colors are particular to fall because their pigment is created only when the temperature drops.
Fall is often some combination of bright sunlight but cooler air, and it’s under these conditions that amber, red, and magenta hues in leaves can be produced. Consequently, autumns with a lot of sunny days and cold nights will actually have the brightest red colors. The intensity of the leaves will vary based on moisture and temperature, and sudden frost can stunt more brilliant colors from being revealed.
When leaves start to prepare to fall off the trees come winter, a layer of cells form along the base of its stalk. This formation effectively seals off the movement of sugar from leaf to tree, and when that leaf is blown off, it leaves behind a leaf scar. The remaining sugars are stored in the tree.
The sugars that are left in the leaf react with cell sap to produce anthocyanin, which is a flavonoid compound that presents itself in red, blue, purple, or magenta pigment. The hues of anthocyanin also depend on the plant’s soil acidity. This means that trees in different parts of the world will display different hues of red or magenta. Indeed, some species of trees even are subject to more brilliant reds than others, like maples, sweet gum, and dogwood.
Anthocyanins will also combine and blend with the other yellow and orange pigments in the leaf. Some tree leaves, then, will be multicolored and display different shades of yellow, orange, and red all in a single leaf.
These pigments too, though, will eventually degrade, and a dull brown will remain.
All told, as the leaf shuts down food production for the tree, its many pigments degrade from green to yellow, orange, red, and sometimes purple, until it is brown and dead.
Some scientists also think that why leaves change color has something to do with their evolution and is in fact not even that useful to the tree anymore. They posit that the color may once have been used to attract certain insects, some of which are now extinct:
“Because plants evolve very slowly, we still see the colors. So leaf color is a fossil memory, something that existed for a reason millions of years ago but that serves no purpose now,” suggests Bryan A. Hanson, professor of chemistry and biochemistry at DePauw University.
But as with all beautiful phenomena that we witness on this earth, science can only explain so much, and the rest is just pure magic.
After this look at why leaves change color, take a look at these 21 images from the thousand-year-old mid-autumn festival that’s celebrated all across Asia. Then, check out this research study that suggests the Earth’s vegetation may once have been purple, and not green.
Why More Autumn Leaves Are Red In America And Yellow In Europe: New Theory
A new theory provided by Prof. Simcha Lev-Yadun of the Department of Science Education- Biology at the University of Haifa-Oranim and Prof. Jarmo Holopainen of the University of Kuopio in Finland and published in the Journal New Phytologist proposes taking a step 35 million years back to solve the color mystery.
The green color of a tree’s leaves is mainly due to chlorophyll pigment. The change in color to red or yellow as autumn approaches is not the result of the leaves’ dying, but is rather the result of a series of processes – which differ between the red and yellow autumn leaves. When the green chlorophyll in leaves diminishes, the yellow pigments that already exist become dominant and give their color to the leaves. Red autumn leaves result from a different process: As the chlorophyll diminishes, a red pigment, anthocyanin, which was not previously present, is produced in the leaf. These facts were only recently discovered and led to a surge of research studies attempting to explain why trees expend resources on creating red pigments just as they are about to shed their leaves.
Explanations that have been offered vary and there is no agreement on this as of yet. Some research suggests that the red pigment is produced as a result of physiological functions that make the re-translocation of amino acids to the woody parts of the tree more efficient in setting up its protection against the potential damage of light and cold. Other explanations suggest that the red pigment is produced as part of the tree’s strategy for protecting itself against insects that thrive on the flow of amino acids. But whatever the answer is, these explanations do not help us understand why the process of creating anthocyanin, the red pigment, does not occur in Europe.
An evolutionary ecology approach infers that the strong autumn colors result from the long evolutionary war between the trees and the insects that use them as hosts. Insects tend to suck the amino acids from the leaves in the fall season, and later lay their eggs, to the detriment of the trees. Aphids are attracted to yellow leaves more than red ones. Trees that expend the energy to color their leaves red may benefit from fewer aphids and fewer aphid eggs. In this case too, the protective logic of red pigmentation may be sound, but why are there more yellow-leaved trees in fall in Europe, if red leaves are an advantage?
According to the theory provided by Prof. Lev-Yadun and Prof. Holopainen, until 35 million years ago, large areas of the globe were covered with evergreen jungles or forests composed of tropical trees. During this phase, a series of ice ages and dry spells transpired and many tree species evolved to become deciduous. Many of these trees also began an evolutionary process of producing red deciduous leaves in order to ward off insects. In North America, as in East Asia, north-to-south mountain chains enabled plant and animal ‘migration’ to the south or north with the advance and retreat of the ice according to the climatic fluctuations. And, of course, along with them migrated their insect ‘enemies’ too. Thus the war for survival continued there uninterrupted.
In Europe, on the other hand, the mountains – the Alps and their lateral branches – reach from east to west, and therefore no protected areas were created. Many tree species that did not survive the severe cold died, and with them the insects that depended on them for survival. At the end of the repeated ice ages, most tree species that had survived in Europe had no need to cope with many of the insects that had become extinct, and therefore no longer had to expend efforts on producing red warning leaves.
According to the scientists, evidence supporting this theory can be found in the dwarf shrubs that grow in Scandinavia, which still color their leaves red in autumn. Unlike trees, dwarf shrubs have managed to survive the ice ages under a layer of snow that covered them and protected them from the extreme condition above. Under the blanket of snow, the insects that fed off the shrubs were also protected – so the battle with insects continued in these plants, making it necessary for them to color their leaves red.
Recently we’ve discussed why leaves are green. Now the summer is over and soon the trees will change colors. Do you know why leaves turn yellow in autumn? This article is devoted to color change of green plants with change of seasons.
Deciduous trees in the temperate zones change their colors in autumn. Being green in summer, they turn orange, yellow, purple, red or even brown. This transformation is triggered by day shortening in September. The photoreceptor phytochromereacts to the change in the length of the day. When the days are shortening, plants green pigment chlorophyll starts to break down. Chlorophyll destruction unmasks accessory pigments, e.g. carotenoids that have yellow-orange colors.
The cause of initial degradation of chlorophylls is plants requirement of nitrogen, which is a part of the chlorophyll molecule. Plants reuse nitrogen from chlorophyll because reserves of this essential macro element are depleted in autumn. On the other hand, carotenoids are composed almost entirely of carbohydrates. They do not contain elements that are in short supply in autumn. At the same time, these accessory pigments continue to protect leaves against photooxidative damage after chlorophyll breakdown. Thus, plants that do not accumulate other accessory pigments besides of carotenoids have autumn leaves painted in orange and yellow colors.
Red-purple coloration of leaves is determined by another pigments anthocyanins. Anthocyaninsare newly synthesized by plants in autumn, contrary to carotenoids which preexist in chloroplasts along with chlorophylls. The most probable meaning of such synthesize is photoprotection of leaves from photo-oxidative damage, risk of which is especially high in autumn. Consequently, functional leaves enable a better resorption of nutrients, especially nitrogen and phosphorus.Also, the coevolution hypothesis is worth mentioning, according to which autumn coloration is a signal for insects that migrate to the trees in autumn.Alteration of green leaves colormight deter insects from occupying the soon-to-be-shed leaves. In such a waytrees can defend themselves from insects.
Brown coloration of the leaves usually indicates the deathof their cells. Besides, combined presence of anthocyanins and chlorophylls can also result in brown color of the leaves.
Recently we received the following question:
“hi! i wonder why leaves stop being green at autumn? i mean how do they know and why color are so different?”
In this section we did our best to answer it and discussed related concepts. Have your own interesting how-it-works questions? The next article may be devoted to one of them, so don’t hesitate to ask!
The science behind why leaves change color in autumn
Ah, autumn—the air is crisper and the trees are turning brilliant shades of gold, red, and brown. In the temperate areas of the world, it gets very cold in the winter and there is not much sunlight, which the trees need to feed themselves. Leaves are delicate and can’t survive the winter, so the tree prepares itself for the cold by taking all useful things from the leaves before they fall. This preparation process is what causes the leaves to display their striking autumn colors. There’s a good reason why different trees have leaves that turn different colors.
Preparing for winter
In the summer, most trees have green leaves because they contain the pigment chlorophyll. This pigment is also used to convert sunlight into energy for the tree. In summer, chlorophyll is constantly replaced in the leaves. When it gets cold, the plants stop making chlorophyll and it breaks down into smaller pieces. The trees can reuse the nitrogen that is in the chlorophyll molecule. This is why leaves change colors before they fall off of the tree; the important nutrients that can be reused are taken out of the leaf. The time when leaves start changing color is more dependent on light than on temperature so leaves start changing color at about the same time each year. When deciduous trees reach this light threshold, carbohydrates are transferred from the leaf to the branch and no new minerals are brought in. The trees prepare to separate with their leaves.
A rainbow of autumn colors
The green color of chlorophyll is so strong that it masks any other pigment. The absence of green in the fall lets the other colors come through. Leaves also contain the pigments called carotenoids; xanthophylls are yellow (such as in corn) and carotenes are orange (like in carrots). Anthocyanins (also found in blueberries, cherries) are pigments that are only produced in the fall when it is bright and cold. Because the trees cut off most contact with their leaves at this point, the trapped sugar in the leaves’ veins promotes the formation of anthocyanins, which are used for plant defense and create reddish colors.
However, trees in the fall aren’t just yellow and red: they are brown, golden bronze, golden yellow, purple-red, light tan, crimson, and orange-red. Different trees have different proportions of these pigments; the amount of chlorophyll left and the proportions of other pigments determine a leaf’s color. A combination of anthocyanin and chlorophyll makes a brown color, while anthocyanins plus carotenoids create orange leaves.
Low temperatures still above the freezing point help to produce anthocyanin, which produces a bright red color. An early frost weakens the color by destroying the creation of anthocyanins, however. Drought can also cause leaves to fall off without changing color. Where just a few tree species dominate, like in New England and Northeast Asia, color displays are intense but short. Diverse forests mean a longer display. Cloudy and warm falls like those in Europe cause dull colors.
Where the stem of the leaf attaches to the tree, a layer of cells forms that eventually cuts the tissue that attaches the leaf to the tree. There is a closed scar on the branch where the leaf was attached; the leaf is then free to fall when prompted by wind, gravity, rain, and so on. When the leaves die and the chloroplasts are completely broken down, leaves turn a boring brown.
And that is the science behind why the leaves that fall in the autumn are everything from red and yellow to orange and bronze to, finally, brown.
Click to enlarge
With autumn looming on the horizon, the leaves on some trees have already begun the transition towards the vibrant hues of autumn. Whilst this change may outwardly seem like a simple one, the many vivid colours are a result of a range of chemical compounds, a selection of which are detailed here.
Before discussing the different compounds that lead to the colours of autumn leaves, it’s worth discussing how the colours of these compounds originate in the first place. To do this we need to examine the chemical bonds they contain – these can be either single bonds, which consist of one shared pair of electrons between adjacent atoms, or double bonds, which consist of two shared pairs of electrons between adjacent atoms. The colour causing molecules in autumn leaves contain systems of alternating double and single bonds – this is referred to as conjugation. A large amount of conjugation in a molecule can lead to them being able to absorb wavelengths of light in the visible spectrum. This leads to the appearance of colour.
Chlorophyll is the chemical compound responsible for the usual, green colouration of most leaves. This chemical is contained within chloroplasts in the leaf cells, and is an essential component of the photosynthesis process via which plants use energy from the sun to convert carbon dioxide and water into sugars. For the production of chlorophyll, leaves require warm temperatures and sunlight – as summer begins to fade, so too does the amount of light, and thus chlorophyll production slows, and the existing chlorophyll decomposes. As a result of this, other compounds present in the leaves can come to the fore, and affect the perceived colouration.
Carotenoids & Flavonoids
Carotenoids and flavonoids are both large families of chemical compounds. These compounds are present in the leaves along with chlorophyll, but the high levels of chlorophyll present in the summer months usually masks their colours. As the chlorophyll degrades and disappears in autumn, their colours become more noticeable – both families of compounds contribute yellows, whilst carotenoids also contribute oranges and reds. These compounds do also degrade along with chlorophyll as autumn progresses, but do so at a much slower rate than chlorophyll, and so their colours become visible. Notable carotenoids include beta-carotene, the cause of the orange colour of carrots, lutein, which contributes to the yellow colour of egg yolks, and lycopene, which is also responsible for the red colour of tomatoes.
Anthocyanins, are also a member of the flavonoid class of compounds. Unlike carotenoids, anthocyanins aren’t commonly present in leaves year-round. As the days darken, their synthesis is initiated by increased concentration of sugars in the leaves, combined with sunlight. Their precise role in the leaf is still unclear – there has been some suggestion, however, that they may perform some kind of light-protective role, allowing the tree to protect its leaves from light damage and extend the amount of time before they are shed. In terms of their contribution to the colour of autumn leaves, they provide vivid red, purple, and magenta shades. Their colour is also affected by the acidity of tree sap, producing a range of hues.
The graphic in this article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. See the site’s content usage guidelines.
References & Further Reading
- The Chemistry of Fall’s Foliage – ACS Undergrad
- Pigment Dynamics & Autumn Leaf Senescence – D W Lee & others
- Quantitive Investigations of Leaf Pigments – J E Sanger
- The Role of Anthocyanins in Senescing Leaves – T S Feild & others
What Month Do Leaves Change Color and Fall Off Trees?
Now that you’ve survived the last hot day of the year, you’re looking forward to the next big thing. You can unpack your sweaters and grab your first pumpkin spice latte whenever you please. But, when will the leaves change?
That is the must-see moment of the fall. It is mesmerizing to watch the swathes of green trees fade away–replaced by dazzling amber, maroon, gold and bronze hues. You’ve got to soak up the leaves’ beauty while they’re here because they don’t last long.
Learn what month your tree leaves will likely change color and fall this autumn. Or figure out why your tree still has leaves when others don’t.
Fall Foliage Forecast (Northeast, Midwest, South, and West)
Across the country, October is the month for leaf color and drop! More exact dates are below.
Of course, if there’s unusual weather in your area, like an especially dry season or early fall, trees may lose leaves sooner or later. Because weather has such a large impact, these dates may vary. The best combination for stellar leaf color? Dry, warm days followed by cool nights without frost and little wind to blow the leaves off the tree.
- Leaf Fall Dates in the Northeast: You’ll see peak fall color in mid-October. In northern parts of Maine, New Hampshire, Vermont, and New York, you could see this as early as late September. Tree leaves will start falling either early or late October – about a week after peak color.
- Leaf Fall Dates in the Midwest: Expect leaf color to be the best around mid-October. Northern Minnesota, Wisconsin and Michigan will see this a bit sooner in early October. Leaves will then begin to fall a week later, so mid-to-late October.
- Leaf Fall Dates in the South: Leaves in the South will showcase peak color in late October or early November. In West Virginia, east Tennessee, western Virginia, or western North Carolina, you could see this in mid-October. Leaves will then fall one week after that, so anywhere from late October to mid-November.
- Leaf Fall Dates in the West: Leaves in the West will change in early or mid-October. In Washington, Oregon and Northern California, you’ll see peak leaf color in late October. Denver leaves change the earliest in late September. Leaves will fall about one week later, so anywhere from early to late October.
Why do my trees still have leaves when other nearby trees are bare?
Some tree species, particularly oaks and beeches, keep their leaves much longer than other trees. In fact, these leaves will dry out, but cling to the tree until a storm or wind blows them off.
If only a few of your trees’ branches still have their leaves, that could mean there’s a problem. It’s best to play it safe. Have a certified arborist come out and inspect your tree during a free consultation.
How do trees change in the fall?
Pine trees and other conifers keep their greenery all year, even in cold climates!
Rocky Mountain National Park
NPS Phot / M. Reed
What do they do have in common?
Both conifers and broadleaf trees try to save water during the winter without freezing into giant, frozen vegetables. The trick is that a tree can survive having ice crystals between its cells, but dies when the cells freeze. They stop this from happening by taking advantage of a really cool chemical reaction in water.
When you, or a tree, dissolve something like sugar or salt in water it becomes more difficult for the water to freeze. So, in the fall, trees gradually dehydrate themselves to increase the concentration of sugar in their cells. Extra water becomes insulation for the sugar-heavy cells, making them even more resilient to freezing.
Ice can still be a danger for the outside of a tree though. Sometimes, snow or melting ice can become so heavy on tree branches that they break. While some species are super flexible to stop this from happening, others aren’t as lucky.
Fall is full of changes for all living things, and it’s the time of year when many of our national parks put themselves to bed for the winter. As the air gets colder and the colors of the trees change, remember that there is always more happening than we can see.