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Why Don’t Evergreens Lose Their Leaves?

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Coastal Redwood, El Dorado Hills (9/7/17) John Poimiroo

Actually, they do.  It just doesn’t happen all at once, with few exceptions.

Evergreen trees have both broad leafs and needles. Madrone, magnolia and photinia are examples of broadleaved evergreens, while pine, fir, cedar, spruce, and redwood have needled leaves.

Evergreen needles can last anywhere from a year to 20 years, but eventually they are replaced by new leaves. When that happens, the old needles turn color and drop, but not all together and not as dramatically as deciduous trees (e.g., maple, oak, dogwood, alder, birch).

The reason needles are green is that they are full of chlorophyll which photosynthesizes sunlight into food for the tree. It also reflects green light waves, making the needles look green.

Needles, just like deciduous leaves, contain carotenoid and anthocyanin pigments. You just don’t see them until the green chlorophyll stops being produced. Once that happens, hidden carotenoids (yellow, orange and brown) emerge, as is seen in the above photograph.

Additionally, red, blue and purple Anthocyanins – produced in autumn from the combination of bright light and and excess sugars in the leaf cells – also emerge once the chlorophyll subsides.

Yes, even evergreen leaves change color… eventually.

Fremont cottonwood and coastal redwood, Davis (9/16/20) Phillip Reedy

Evergreens that drop leaves at one time include the: Conifers Larch, Bald Cyprus and Dawn Redwood.

In snowy regions, evergreen trees are able to carry snow because the waxy coating on needles, along with their narrow shape, allows them to retain water better by keeping it from freezing inside (which would otherwise destroy the leaf).

Needles also prevent snow from weighing down and breaking branches. Finally, needles allow an evergreen tree to sustain the production (though slowed) of chlorophyll through winter. Whereas, broadleaved deciduous trees would be damaged if they kept producing chlorophyll and didn’t drop their leaves.

Evergreen trees do lose their leaves and the leaves do change color. It just isn’t as spectacular. 

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Why Do Deciduous Trees Lose Their Leaves?

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Snowcreek (11/2/15) Alicia Vennos

It’s survival not just of the fittest, but of the wisest.

Deciduous trees drop their leaves in order to survive.  As days grow shorter and colder, deciduous trees shut down veins and capillaries (that carry water and nutrients) with a barrier of cells that form at the leaf’s stem.

Called “abscission” cells, the barrier prevents the leaf from being nourished. Eventually, like scissors, the abscission cells close the connection between leaf and branch and the leaf falls.

Had the leaves remained on branches, the leaves would have continued to drink and, once temperatures drop to freezing, the water in the tree’s veins would freeze, killing the tree.

Further, with leaves fallen, bare branches are able to carry what little snow collects on them, protecting them from being broken under the weight of the snow. So, by cutting off their food supply (leaves), deciduous trees survive winter.

The fallen leaves continue to benefit the tree through winter, spring and summer by creating a humus on the forest floor that insulates roots from winter cold and summer heat, collect dew and rainfall, and decompose to enrich the soil and nurture life.

It’s a cycle of survival, planned wisely. 

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Why do Leaves Change Color?

Chlorophyll Molecule (Wikipedia)

Leaves on deciduous trees change color in autumn from green to various hues of lime, yellow, gold, orange, red and brown because of a combination of shorter days and colder temperatures.

Throughout spring and summer, green chlorophyll (which allows trees to absorb sunlight and produce nutrients) is made and replaced constantly.

However, as days grow shorter, “cells near the juncture of the leaf and stem divide rapidly but do not expand,” reports Accuweather.com. “This action of the cells form a layer called the abscission layer.

“The abscission layer blocks the transportation of materials from the leaf to the branch and from the roots to the leaves. As Chlorophyll is blocked from the leaves, it disappears completely from them.”

That’s when vivid yellow xanthophylls, orange carotenoids and, due to a different process, red and purple anthocyanins emerge.

Orange is found in leaves with lots of beta-carotene, a compound that absorbs blue and green light and reflects yellow and red light, giving the leaves their orange color.

Yellow comes from Xanthophylls and Flavonols that reflect yellow light. Xanthophylls are compounds and Flavonols are proteins.  They’re what give egg yolks their color.

Though always present in the leaves, Carotenoids and Xanthophylls are not visible until Chlorophyll production slows.

Red comes from the Anthocyanin compound. It protects the leaf in autumn, prolonging its life. Anthocyanins are pigments manufactured from the sugars trapped in the leaf, giving term to the vernacular expression, “the leaves are sugaring up.”

The best fall color occurs when days are warm and nights are clear and cold. California’s cloudless skies and extreme range of elevations (sea level to 14,000′) provide ideal conditions for the development of consistently vivid fall color, as seen in these reports. 

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The Science of Changing Leaves

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Is red a defensive color? (11/22/18 – El Dorado Hills) John Poimiroo

Last year, Smithsonian.com posted a fascinating time-lapse video of leaves transforming from chlorophyll-filled green to tones of yellow, red and brown. The video was accompanied by an article explaining how leaves change color and some misconceptions about the process.

The video was created by Owen Reiser, a mathematics and biology student at Southern Illinois University Edwardsville. Reiser, Smithsonian.com reports, took 6,000 photos of leaves to weave the video together.

CaliforniaFallColor.com has reported previously how the change of leaf color results from the loss of chlorophyl, due to shorter days and fewer nutrients. Though, David Lee, Professor Emeritus of biological sciences at Florida International University and author of Nature’s Palette, The Science of Plant Color, says many (including us) have misreported (we won’t make the mistake again) that yellow and red leaves change the same way, when they do not.

Lee states in the Smithsonian.com article that the breakdown of chlorophyll in the leaves does reveal yellow and orange (carotenoids) hidden beneath, but that red (anthocyanin) pigments are produced within the leaves as they die.

There are two schools of thought as to why this happens. One is that the red color is a defensive measure to make the plants look an unhealthy red as the leaf dies, protecting it from plant-eating bugs and animals which are conditioned not to eat red foliage.

The other thought is that red is a form of photo protection. Horticulturist Bill Hoch, Smithsonian.com reports, believes red’s wavelength helps shield the leaf by absorbing excess light allowing the plant to more efficiently remove nitrogen from the proteins that are breaking down and send that nutrient back to tree limbs and roots, saving as much of it as possible before winter.

Whatever the cause, the result is spectacular and less than a month away from being seen in California.

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Climate, Conditions and Color

Smoke from the Rough Fire obscured aspen turning yellow at Lake Sabrina (8/24/15) John Poimiroo

Environmental changes affect fall color. California is experiencing a prolonged spate of hot, dry and smoky air. That dehydrates the soil and reduces photosynthesis, which affects fall color.

CaliforniaFallColor.com has been monitoring news reports of whether this autumn is predicted to be more colorful or less than in previous years. Sources in New Hampshire, Minnesota and Southwest Colorado predict dull color due to drought. North Carolina is getting mixed reviews. Wisconsin is estimated to have a normal autumn, and Maryland is optimistic for a vibrant Autumn due to moisture and hot days.

As for California, we conclude that the beauty of our show will depend upon conditions at specific locations and that no overall prediction for a given region with the state or California as a whole can be made with any reliability. Nevertheless, late summer hot, dry days and smoky air will dull fall color in many places.

“Soil moisture is essential to tree health, obviously, so if there has not been enough moisture at fall color time, color could be delayed, just plain dull, or leaves can die early without changing color,’’ Val Cervenka, forest health program coordinator for the Minnesota Department of Natural Resources was reported in the Duluth News Tribune, this week, as saying. “Trees that are under stress usually show it first in their leaves. Since so much of a tree’s energy goes into producing leaves, the tree can conserve energy by simply dropping the leaves, like it does before it goes dormant in the winter,” he continued.

Marissa Y. Thompson, Ph.D. of New Mexico State University wrote on the university’s website in 2001 that, “Plants can be affected in both a positive and negative manner by smoke.” She continued that “Smoke, produced by combustion of some material, means that there is increased carbon dioxide over a limited area. This is good for the plants and can increase their growth if there is sufficient light.

“The smoke particles that we see, however, are particulate pollution which can coat the leaf surface, reducing photosynthesis. These particulates can also clog stomatal pores, reducing gas exchange in the leaf. These effects are bad for plants,” Thompson concluded.

Science is often torn between two conclusions, i.e., more CO2 resulting from combustion is good for plants, however smoke particles can reduce photosynthesis which is not good for plants.

Our conclusion is that the smoke caused by this autumn’s earlier-than-usual wildfire season will, on the whole, not be good for fall color. Combined with hot, dry days it has desiccated the leaves on many trees – particularly those that were stressed from disease or localized drought. That means, less dramatic fall color.

Further, smoke particulates – should they remain soiling our air – will reduce the beauty of whatever fall color appears, because fewer light waves will make it through the smoky atmosphere to illuminate the leaves.

That’s a dismal prediction for this early in the year. So, we should note that it’s still two weeks from the Autumnal equinox and a lot can happen that could change this within the next month.

  1. It could rain. Some long-range forecasts predict rain at the end of September. Where moisture falls, forests will thrive, leaves will remain fresh and fall color will appear in dazzling displays.
  2. The air could clear. The number and ferocity of California’s wildfires have exceeded normality. They’ve been fed by lightning strikes, high temperatures and wind. A drop in any of these influences could return the state to a more normal fire season.

So, be informed, but don’t lose your enthusiasm. Despite the disappointing present, there will be bright spots of gorgeous fall color to find along the backroads and byways of California. And, when they can be seen, we will report them.

Orange Friday

Red maple, El Dorado Hills (11/26/19) John Poimiroo

There are three ways to spend the Friday following Thanksgiving Day:

  • Stand in line waiting to purchase stuff that will soon be forgotten,
  • Sit at home watching football games or
  • See the last bright splashes of fall color with friends and family.

My Orange Friday will be spent outside with friends and family, reveling in the moment when autumn brings us together.

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Giving Thanks and Looking Back at 2019

On this Thanksgiving Day, CaliforniaFallColor.com is thankful to the many color spotters and photographers who contributed reports, photographs and videos in 2019.

They include (from first leaf): Jeff Simpson, Martha Fletcher, Robert Kermen, Bob Simms, Lori Quillen, Julie Kirby, Donna Mercer, Dakota Snider, Jeff Luke Titcomb, Michael Beatley, Jared Smith, Anirudh Natekar, Michelle Pontoni, Justin Legge, John Ehrenfeld, Aaron Thom, Philip Reedy, Suzanne Kovacs, Mike Schaper, Alena Nicholas, Trent Vierra, Kathy Jonokuchi, Leor Pantilat, Dylan Ren, Dan Rastler, Ryan Boyd, Gigi de Jong, Laura Jean, Mark Harding, Elliot McGucken, Steve Shinn, Alicia Vennos, Liz Grans, Ann Hale-Smith, Clayton Peoples, Logan Alexander, Terry Willard, Kurt Lawson, Risa Wyatt, Jeri Rangel, Chien-Chang Kyle Chen, Fares Alti, Kent Gordon, Lance Pifer, Walt Gabler, Laura Christman, Gene Miller, Dan Varvais, Ravi Ranganathan, Jun Hong, Kathleen DiGregorio, Steve Arita, Roger Zhang, Mel Fechter, Shanda Ochs, Dan Mata, Gabriel Leete, Max Forster, Benjamin Vu, Son Nguyen, Vishal Mishra, Bea Ahbeck, Niven Le, Mark Hanning-Lee, Frank McDonough, Chance Gordon, Charles Hooker, Jim Adams, Susan Hanlon, Gillian Espinosa, Melani Clark, Mike Caffey, Anson Davalos, Deepa Yvaraj, Allison Hastings, Ben Carlson, Mohammed Hossain, John Jackson and Ron Tyler, who produced the above video.

Special thanks are expressed to Inyo County Tourism, Bishop Area Chamber of Commerce & Visitors Bureau, Mono County Tourism, Mammoth Lakes Tourism, Redding Convention & Visitors Bureau, and the Shasta Cascade Wonderland Association for underwriting California Fall Color, and to the many reporters and media who carried our reports and gave attention to what we have shown about California’s fall color.

If we missed you, please know it wasn’t intentional. We are truly indebted to every contributor.

Of course, this list is incomplete without mentioning my wife, Joan, who has driven the car and pulled it to the shoulder so that I could jump out to photograph particularly beautiful locations; humored my recording of color percentages, species and elevations; pointed out spectacular color; and tolerated my exuberance in showing her countless stunning photographs taken by our contributors.

Of course, our deepest thanks go to the many tens of thousands of people who have read, followed, reacted and commented here and on our social media pages. You are, after all, the reason we do this.

Above is our video impression of autumn in California, this year. We produce a new video each autumn. To see them all, CLICK HERE.

The photographs selected for this year’s video represent: what happened this autumn, the extent and diversity of fall color across the state, and some of the finest photographs taken in 2019.

If you would like your photographs considered for inclusion in next autumn’s video, submit “horizontal” pictures of fall color taken in places not often photographed. As competition is stiffest among pictures taken at the most photographed destinations.

Autumn doesn’t end today. It continues for nearly a month longer. We’ll continue to post photos and reports, as received. Though today, we begin to dial back reports and will post them less frequently. We’ve also stopped sending  weekly reports to meteorologists, travel and outdoor writers.

So, enjoy your Thanksgiving Day and plan an Orange Friday of fall color spotting, tomorrow.

See you next autumn, dude.

California – Peak (75-100%) GO NOW! – In our hearts, California is always peaking.

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Looking Back at Autumns Past

Tomorrow, we post our annual Thanksgiving Day message and video review of 2019.

It will be our eighth annual “California Fall Color Looks Back” video. As, although CaliforniaFallColor.com went live in 2009, it wasn’t until 2012 that we began posting video reviews.

In advance of seeing “California Fall Color Looks Back at 2019,” we thought you might like to see those from years past.

Ron Tyler created each video. Ron is head of the Tyler Marketing Group, an El Dorado Hills-based marketing communications consultancy with expertise in social media, product marketing and video.

Each of the photographs selected for these videos is representative of what happened that autumn, the extent and diversity of fall color seen across the state, and some of the finest photographs taken that year.

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Statewide Summary

North Lake, Bishop Creek Canyon (9/30/16) Elliot McGucken

A year ago, CaliforniaFallColor.com was reporting more orange in the Eastern Sierra than Sunkist has. What a difference a year makes.

This autumn, Peak color is arriving a week and a half late with Near Peak color only just reported from Virginia Lakes and Sagehen Summit, both in Mono County (US 395).

The late arrival of fall color – which historically has peaked in a few locations before the first day of autumn – has exasperated Eastern Sierra fall color observers and complicated answering whether autumn’s show is on time or not.

That’s because locations in the Northern Sierra and Southern Cascades have filed photos showing Patchy color, well before the region’s mid-October norm for fall color.

Most definitely, fall color is late in the Eastern Sierra, but it’s too early to say it will be late everywhere.

What seems to be certain is that there’s plenty of lush foliage in the forests, because of last winter’s heavy snow and rainfall, meaning that the display of fall color this autumn could be one of the best (should weather conditions permit).

Ideal conditions for the development of vibrant fall color require: healthy trees, clear skies, warm days and cold nights. So far, Mother Nature has been providing those conditions.

Now that peak color is appearing, it will spread rapidly with Peak color likely to appear this weekend and next week (Sept. 27 – Oct. 2) at elevations above 9,000’ in the Eastern Sierra. It then descends by elevation at a general rate of 500 feet per week, meaning that if it is peaking in one canyon at 9,500’, the following week it will be peaking at 9,000’ and so on.

There are a few exceptions to this rule of thumb, of course. Some locations (Sagehen Summit, as an example) peak earlier, while others (Tioga Pass) peak later than similar elevations.

High elevations do not inhibit seeing fall color, as paved roads lead right to aspen groves and tree-lined lakes in numerous canyons along the eastern side of the Sierra, making fall color viewing easily reached.

Elsewhere in the Sierra Nevada mostly Patchy color is being seen with Hope Valley (CA-88, Carson Pass) still a week away from Peak color. Yosemite, the Western Sierra and the Gold Country will peak from mid October to mid November

California’s vineyards peak by grape variety, between mid October and late November.

The Shasta Cascade region (northeast California) is reporting early patchy color at locations, but the region will not be peaking until mid October.

Southern California fall color spotters have not yet reported from the San Bernardino, San Gabriel, Santa Monica, San Jacinto or Laguna mountains. These areas are typically mid October to late November peaks, depending on location.

And, California’s urban forests peak in November, its deserts in December.

Finally, we can admit that – for the moment – Sunkist has more orange than California has fall color.

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Super Bloom Spring

Superbloom, Temblor Range, Carrizo Plain National Monument (Sumikophoto |Dreamstime.com)

With above-record rainfall drenching California this winter, wildflower super blooms are possible this Spring in Death Valley (late – Feb.), Anza Borrego State Park (mid-Mar.), the Antelope Valley Poppy Reserve near Lancaster (early-Apr.) and the Carrizo Plain National Monument (early-Apr.).

Tiffany Camhi of KQED, San Francisco’s public television station, reported today that with a little more rain, a super bloom of poppies, lupine, owl’s clover and other wildflowers is possible.

The National Park Service reports that “The best blooms are triggered by an early, winter-type rainstorm in September or October, followed by an El Niño weather pattern that brings above average rainfall to the Desert Southwest.”

What’s needed for this rare profusion of wildflowers are preceding years of drought and massive winter rainfalls. Both have happened, so it’s “possible.”