,

Eastern vs. Pacific

Eastern dogwood, The Ahwahnee, Yosemite NP (10/8/21) Julie Kirby

When it comes to dogwood (Cornus), all the native trees in California have white bracts (flowers) while those in the east are pink. So, if you see a pink dogwood anywhere in California, it is a transplant from the eastern U.S.

Eastern dogwood, The Ahwahnee, Yosemite NP (10/8/21) Julie Kirby

In Yosemite Valley, a few pink-flowering dogwood (cornus florida) were planted by residents and have been allowed to remain growing in the park. One at The Ahwahnee is often confusing to park visitors because of the pink color tinting its stems and showy red fruit.

In springtime, eastern dogwood have profuse displays of pink bracts. They look like flowers, but they’re not. Bracts are leaves which have evolved to appear to be flower petals. They help in attracting pollinators. The dogwood’s actual flowers reside at the center of the bracts and have their own modest petals.

Pacific dogwood (cornus nuttallii) are beautiful in their own right and the banks of the Merced River are lined with these flowering white trees in May.

So, if you happen to see a pink dogwood in Yosemite National Park, it doesn’t belong there. And, if you think otherwise, then you’re just barking up the wrong tree.

,

Why Don’t Evergreens Lose Their Leaves?

This image has an empty alt attribute; its file name is JP-Redwood-EDH-04897-1030x687.jpg
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.

This image has an empty alt attribute; its file name is Phillip-Reedy-DSC_2575-crop-804x1030.jpg
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. 

This image has an empty alt attribute; its file name is Red.png
,

Why do Deciduous Trees Lose Their Leaves?

This image has an empty alt attribute; its file name is AV-Snowcreek-3-600x338.jpg
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. 

,

The Science of Changing Leaves

This image has an empty alt attribute; its file name is John-Poimiroo-Orange-Friday-2-773x1030.jpg
Is red a defensive color? (11/22/18 – El Dorado Hills) John Poimiroo

A couple of years ago, Smithsonian.com posted a 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.

Leaves that change due to the loss of chlorophyl as a result of shorter days and fewer nutrients tend to turn orange or yellow. Though David Lee, Professor Emeritus of biological sciences at Florida International University and author of Nature’s Palette, The Science of Plant Color, says that many yellow and orange leaves do not change the same way as red leaves.

Lee states in a Smithsonian.com article that the breakdown of chlorophyll in 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 thoughts as to why this happens. One is that the red color is a defensive measure to make the plants appear unhealthy as the leaf dies, protecting the tree 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.

This image has an empty alt attribute; its file name is Red-e1569014164278.png
,

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. 

Peak fall color will begin appearing in the Eastern Sierra above 9,000 feet (you can drive right to it) some time during the last two weeks of September.

This image has an empty alt attribute; its file name is Red.png
, ,

Are You Ready?

Chinese Tallow Tree, Davis (8/16/21) Philip Reedy

“Fall is just around the corner,” writes color spotter Phillip Reedy. He was out for a walk in Davis when he spied this bit of exotic color lying amidst the debris of spent seed pods.

Early color is not unusual, particularly during a drought. The normal triggers of color change are upset by lack of water and other factors.

Typically, it is less light from days shortening and colder temperatures that triggers the process of leaves changing color. Lots of sun and heat are the opposite of that, but when plants lack water they become stressed and when they do, anything goes, including their leaves.

The Duluth News Tribune reported Val Cervenka, forest health program coordinator for the Minnesota Department of Natural Resources 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,”

CaliforniaFallColor.com has been monitoring what’s happening across the country. California isn’t the only location where drought is a factor. Minnesota and Colorado have been experiencing a dryer than normal summer with naturalists predicting early fall color.

In Western Massachusetts, it’s the opposite. It’s been a wetter year than normal. So, you’d think they’d be predicting delayed color. Not so. Weakened maples were showing signs of change in early August and color spotters across Western Mass are gearing up for an early show.

In our experience, lots of water means the color appears as normally, but stays longer. Little water means some of the color begins to show sooner than normal and doesn’t last long. It’ll still be beautiful, but when we post “Go Now!”, we mean it. As soon as you see it Near Peak, go. Are you ready?

, ,

Early Dormancy

Blue Oak are peaking early in the Sierra Foothills (7/18/21) John Poimiroo

Blue oak (Quercus douglassii) are native to the hot, dry slopes of California’s interior valleys. They survive drought through a series of mechanisms, including the blue, waxy layer atop their leaves which helps reduce water loss in summer.

They need very little water. Blue oak will survive on 15 – 30″ of rain a year. Too much water is what kills them. Bartlett Tree Research Laboratories lists excessive watering as the leading killer of established Blue oak in the landscape.

In a normal year, Blue oak leaves turn golden yellow and pastel pink and orange during fall. However, in hot, dry years like this one, leaves achieve early dormancy, turn color suddenly and drop. That’s happening this week in the Sierra foothills where suddenly Blue oak are near peak.

  • Blue Oak, Sierra Foothills (Near Peak – 50-7%) GO NOW!
Early Dormancy, Blue Oak, El Dorado HIlls (7/18/21) John Poimiroo
,

We’re Number One!

In losing trees, that is.

According to a study done by LawnStarter, California leads the nation in deforestation.

LawnStarter compared the 50 states and District of Columbia across eight key metrics and over four time periods to determine where tree cover has shrunk most. They found that California led significantly over second-place Oregon in overall ranking, one-year, five-year and ten-year rankings.

Our ignominious accomplishment was described by LawnStarter in this way: “California not only ranked No. 1 overall among the States That Lost the Most Tree Cover, but it also swept every single metric.”

Now, don’t start cheering. Fire was described as a leading cause of tree loss in 2020, resulting from our worst wildfire season ever, “destroying some of its oldest green giants: redwoods, sequoias (sic.) and Joshua trees. California wildfires ravaged over 4 million acres – an area bigger than Connecticut – accounting for 40% of the total acres burned across the U.S.

“California lost more tree canopy than any other state in every time period we logged, mostly due to wildfires but also to drought and pests.” LawnStarter’s press announcement reported.

Why this matters is that the world is losing trees fast. The U.S. is no different. “Between 2009 and 2014, U.S. cities and rural communities collectively lost 36 million trees, per year.” LawnStarter translates that to the equivalent of saving “$96 million annually by lowering our energy bills, cleaning the air and capturing harmful carbon that contributes to climate change.”

Sadly, 2020 may not be California’s record year for wildfire. It could well be in front of us, as this is a drought year with barren reservoirs and high levels of evaporation already recorded.

Being number one in this category is an achievement we ought not celebrate.

Photo credit: B Street, Arcata (12/5/20) Michelle Pontoni

,

Fascinating Frozen Facts

Swinging Bridge, Yosemite Valley (2/6/21) Steve Arita

In winter, the U.S. Fish and Wildlife Service reports, when other trees are dormant, quaking aspen are energy producers. That’s because they “continue to photosynthesize in their greenish-tinged bark, even after their leaves have dropped.”

It is this living bark layer, which contains chlorophyll and can carry out photosynthesis, that makes the aspen so remarkable a winter survivor.

The USFWS continues in its Kenai NWR “Refuge Notebook,” that quaking aspen are well-adapted to the cold. They survive at higher altitudes by staying small. It’s a response to their tolerance for cold and a lack of moisture at higher elevations. Because of this, aspen are often stunted near tree line, but fully grown several hundred feet lower.

Even their root structure is designed for survival, as the aspen’s fibrous sprouts and suckers are “a handy adaptation in marginal climates,” the USFWS explains. The propagation of aspen clones from one massive root network is why aspen tend to all change color at the same time in fall or leaf out together in spring.

Additionally, in summer, it is the shape and thinness of the aspen leaf that allows it to quake (flutter) in the slightest breeze. Its flexible stem prevents wind damage or stripping and may also “improve the photosynthetic rate,” USFWS vegetation ecologist Elizabeth Bella writes.

Who knew that the quaking aspen would be as fascinating when frozen, as it is lovely during autumn?

, ,

A Dry Spell For Mycophiles

Magpie Mushroom (1/8/21) Gabriel Leete

While most Californians are enjoying this winter’s warm, sunny days, mycophile Gabriel Leete is out wandering the woods in disappointment as he dejectedly walks past the ink caps of Coprinopsis picacea, commonly called the Magpie Mushroom in Anderson. Normally, a wet winter causes all sorts of mushrooms to push up. So far, it’s been “fairly slow.”

Few mushrooms at lower elevations have appeared, and at higher elevations, freezing temperatures have retarded their development.

Redlead Roundhead (1/8/21) Gabriel Leete

In his wanderings, Gabriel found a large colony of Leratiomyces ceres commonly known as the Redlead Roundhead pushing up from shredded bark.

Parasola conopilus (1/8/21) Gabriel Leete

Gabriel sent images of Parasola conopilus (formerly called Psathyrella conopilus) and made the point that they soon will be known as Parasola conopilea.

It seems the mushroom was misidentified as a Psathyrella species, when under the microscope mycologists found it to be a Parasola. Then, an error in Latin agreement got the second half of its name corrected from conopilus to conopilea.

That seems too great an amount of attention and revelation for so common a brown mushroom. Parasola conopilea number from the hundreds to the thousands when they are flourishing. Unfortunately, such scenes are infrequent in this dry winter.