Why are California's redwoods and sequoias so big and tall?
A mix of climate, fire, and genetics helped these ancient giants reach record-breaking size.
California is a state of superlatives. The oldest living thing lives here. The largest animal in the history of the world swims off our shores. The hottest temperature ever recorded (134°F / 57°C) baked visitors at Death Valley's Furnace Creek back in 1913 (and it has been nearly as hot recently) California also boasts the highest point in the contiguous United States and arguably the tallest waterfall in the country.
We also have the world's tallest and biggest trees.
California’s giant sequoias and redwoods are nature’s skyscrapers. Redwoods exist in a few narrow pockets in Northern and Central California and into Southern Oregon. Sequoias live exclusively in small groves in central and Northern California with the largest grouping of them found in Sequoia National Park. These two tree species are wonders of the biological world. They are also some of the most magnificent things to behold on the planet.
I have personally climbed the Stagg tree for a New York Times story years ago (see photo below, that's me). The Stagg is the fifth-largest sequoia in the world, and I will forever remember the experience...even though I chickened out a bit and didn't make it to the top.
We are lucky to still have our big trees, what's left of them, anyway. Just a century and a half ago, old-growth redwoods and sequoias were remarkably plentiful. People marveled at them, with some early settlers in California spinning unbelievable yarns of trees that rise from the earth "like a great tower". They also saw them as a bounteous resource, ripe for plunder (mankind, sigh).
By 1900, nearly all of California's tall trees had been purchased by private landowners who saw in the trees not beauty, but dollar signs. By 1950, an estimated 95% of California’s original old-growth coast redwood forests had been logged, particularly along the coast from Big Sur to the Oregon border. For giant sequoias, about one-third of the original groves had been cut down, largely in the late 19th and early 20th centuries before protections were put in place.
Between 1892–1918, the Sanger Lumber Company logged the Converse Basin Grove, one of the largest stands of sequoia in the world, using ruinous clearcutting practices. They cut down 8,000 giant sequoias, some of them over 2000 years old, in a decade-long event that has been described as “the greatest orgy of destructive lumbering in the history of the world.” Only 60-100 large specimens in the grove survived. We wrote about that awful event here.
Today, only a small fraction of the old-growth coast redwood forest remains. The largest surviving stands of ancient coast redwoods are found in Humboldt Redwoods State Park, Redwood National and State Parks and Big Basin Redwoods State Park. It's a wonder and a blessing that there are some left. And even then, they face an uncertain future thanks to climate change.
The remarkable size and height of these incredible organisms are largely due to California's unique geography, though genetics likely play a significant role as well. Before diving into those factors, let’s take a moment to appreciate just how extraordinary these trees truly are.
Sequoias and redwoods are closely related. Both belong to the cypress family (Cupressaceae). The primary difference between sequoias and redwoods is their habitat. Redwoods live near the moist, foggy coast, while sequoias thrive in higher-elevation subalpine zones of the Sierra Nevada. Redwoods are the tallest trees in the world. Sequoias are the biggest, if measured by circumference and volume. Redwoods can grow over 350 feet (107 m). The tallest tree in the world that we know of is called the Hyperion, and it tickles the sky at 379.7 feet (115.7 m). But it is quite possible another tree out there is taller than Hyperion. Redwoods are growing taller all the time, and many of the tallest trees we know of are in hard-to-reach areas in Northern California. Hyperion was only discovered about a decade ago, on August 25, 2006, by naturalists Chris Atkins and Michael Taylor. The exact location of Hyperion is a secret to protect the tree from damage.
The giant sequoia (Sequoiadendron giganteum) is Earth’s most massive living organism. While they do not grow as tall as redwoods - the average size of old-growth sequoias is from 125-275 feet - they can be much larger, with diameters of 20–26 feet. Applying some basic Euclidean geometry (remember C = πd?), that means that the average giant sequoia has a circumference of over 85 feet.
Sequoias grow naturally along the western slope of the Sierra Nevada mountain range at an altitude of between 5,000 and 7,000 feet. They tend to grow further inland where the dry mountain air and elevation provide a comfortable environment for their cones to open and release seeds. They consume vast amounts of runoff from Sierra Nevada snowpack, which provides groves with thousands of gallons of water every day. But some say the majestic trees face an uncertain future. Many scientists are deeply concerned about how climate change might affect the grand trees, as drought conditions potentially deprive them of water to survive.
The world's largest sequoia, thus the world's largest tree, is General Sherman, in Sequoia National Park. General Sherman is 274.9 feet high and has a diameter at its base of 36 feet, giving it a circumference of 113 feet. Scientists estimate that General Sherman weighs some 642 tons, about as much as 107 elephants. The tree is thought to be 2,300 to 2,700 years old, making it one of the oldest living things on the planet. (To learn more about the oldest thing in the world, also in California, see our recent feature on Bristlecone pines.) Interesting fact: in 1978, a branch broke off General Sherman that was 150 feet long and nearly seven feet thick. Alone, it would have been one of the tallest trees east of the Mississippi.
Many sequoias exist on private land. In 2020, one of the largest remaining private stands of Sequoias in the world - the Alder Creek Grove of giant sequoias - was bought by the Save the Redwoods League conservation group for nearly $16 million. The money came from 8,500 contributions from individual donors around the world. The property includes both the Stagg Tree mentioned above and the Waterfall Tree, another gargantuan specimen. The grove is considered "the Crown Jewel" of remaining giant Sequoia forests.
Redwoods (Sequoia sempervirens), also known as coast redwoods, generally live about 500 to 700 years, although some have been documented at more than 2,000 years old. While wood from sequoias was found to be too brittle for most kinds of construction, the redwoods were a godsend for settlers and developers who desperately needed raw material to build homes and city buildings, to lay railroads, and erect bridge trestles. The construction and subsequent reconstruction of San Francisco following the 1906 earthquake heavily relied on redwood timber, prized for its strength, resilience, and natural resistance to decay, making it a foundational resource for the city’s growth and recovery after the earthquake.
The timber companies who profited from redwoods only began to cut them down in earnest a bit over a century ago. But cut them down they did, with vigor and little regard for the preservation of such an amazing organism. After World War II, California experienced an unprecedented building boom, and the demand for redwood (and Douglas fir) soared. Coastal sawmills more than tripled between 1945 and 1948. By the end of the 1950s, only about 10 percent of the original two-million-acre redwood range remained untouched.
OK, you got this far. I hope. So how did these trees get so big and tall? Most scientists agree it has to do with climate. Sequoias benefit from California's often prodigious snowpack, mentioned above, which seeps into the ground, constantly providing water to the roots of the trees. In addition to the snowpack, the thick (up to 2 feet), fire-resistant bark of sequoias helps protect them from wildfires. This forest ecology helps as well, since the fires themselves clear competing vegetation, allowing more sunlight and nutrients to reach the trees. The temperate climate of California, with its relatively mild winters and summer fog, also helps sustain these giants by moderating temperatures and reducing water loss, creating an environment where sequoias can thrive for centuries.
Conversely, Redwoods get much of their water from the air, when dense fog rolls in from the coast and is held firm by the redwoods themselves and the steep terrain. Because of the unique interplay of ocean currents and climate in California, the amount of fog that is available to trees is highly unusual. The trees' leaves actually consume water in fog, particularly in their uppermost shoots. According to scientists who study the trees using elaborate climbing mechanisms to reach the treetops, in summer, coast redwoods can get more than half of their moisture from fog. (In fact, fog plays a central role in sustaining several of California’s coastal ecosystems.) The reason is that fog is surprisingly dense with water. One study from scientists Daniel Fernandez of California State University, Monterey Bay, showed that a one-square-meter fog collector could harvest some 39 liters, or nearly 10 gallons, of water from fog in a single day.
Another possible explanation for the coast redwood’s remarkable size lies in its extraordinary genome. According to research from the Redwood Genome Project, the coast redwood (Sequoia sempervirens) is hexaploid, meaning it carries six copies of each chromosome in every cell, an extremely rare feature in trees. In contrast, humans and most other plants and animals are diploid, carrying only two sets of chromosomes.
The coast redwood genome is indeed massive, estimated at around 27 billion base pairs, which is approximately nine times larger than the human genome (which has about 3 billion base pairs). While not exactly ten times larger, the general comparison holds and highlights the tree’s genetic complexity.
By comparing the coast redwood’s genome with those of other conifers, researchers have found hundreds of unique gene families, many of which are associated with stress tolerance, wound repair, fungal resistance, toxin metabolism, and the biosynthesis of flavonoids, all compounds that help mitigate cellular stress.
This rich genetic toolkit may contribute to the tree’s legendary resilience, longevity, and ability to grow to extraordinary heights, though the full relationship between genome size and physical traits in redwoods is still being studied.
Yet another factor may be the trees remarkable longevity. They are survivors. The Sierra Nevadas have long experienced dramatic swings in climate, and this age may be yet another of those swings that the trees will simply endure. Or maybe not. For most of the time that redwoods and sequoias have existed, they have done a remarkable job fighting off fires, swings in climate, as well as disease and bug infestations. Because their bark and heartwood are rich in compounds called polyphenols, bugs and decay-causing fungi don't like them. Many trees, not just redwoods and sequoias, have genes that help them resist the typical aging processes that limit the lifespan of animals. For instance, trees can compartmentalize and isolate damaged or diseased wood, preventing the problem from spreading to the rest of the tree.
As the air heats up due to global warming, there is a rising threat to the trees' survival. Warm air pulls moisture from leaves, and the trees often close their pores, or stomata, to maintain their water supply. When the pores close, that prevents carbon dioxide from nourishing the tree, slowing or even halting photosynthesis. The climate in areas where the trees grow hasn't yet experienced the kind of temperatures that might kill them, but we are really just at the beginning of this current era of global warming, and some scientists warn hotter temperatures could doom many trees.
That said, other studies that show the increased carbon that causes warming could actually be good for the trees. According to an ongoing study from Redwoods Climate Change Initiative, California's coast redwood trees are now growing faster than ever. As most people know, trees consume carbon dioxide from the air, so, the scientists argue, more carbon means more growth. However, scientists caution that climate change is not a net benefit. Increased drought, fire risk, and ecosystem stress may ultimately outweigh these temporary growth gains.
We will see. While coast redwoods have shown resilience during recent droughts, with no widespread mortality observed, giant sequoias have not fared as well. In the past decade, drought, bark beetles, and intense wildfires have killed nearly 20% of all mature giant sequoias, a sharp and alarming decline for such a long-lived species.
It all comes down to some kind of balance. Trees may benefit from more carbon, but if it gets too hot, trees could start to perish. That's a bit of a conundrum, to say the least.
The prospect of losing these magnificent trees to climate change is a double whammy. Not only would a mass die-off of trees be terrible for tourism and those who simply love and study them, but trees are some of the best bulwarks we have on the planet to fight climate change. Redwoods are among the fastest-growing trees on earth; they can grow three to ten feet per year. In fact, a redwood achieves most of its vertical growth within the first 100 years of its life. Among trees that do the best job taking carbon out of the atmosphere, you could hardly do better than redwoods and sequoias.
The Archangel Ancient Tree Archive, an organization out of Copemish, Michigan, has been "cloning" California's big trees for nearly a decade. They take snippets of the trees from the top canopy and replant them, essentially creating genetically identical copies of the original tree. It's more like propagating than cloning, but that's what they call it. The group's founder, David Milarch, believes fervently that planting large trees is our best bet in stopping climate change. This is the video story I produced about Milarch back in 2013. It's worth a watch. He's an interesting character with a lot of passion.
Preserving and protecting what's left of these amazing organisms should be a priority in California. These trees are not only part of the state's rich natural legacy, but they offer ample opportunities for tourism and strengthening the economies of the regions where they grow. It's hard to visit Redwood National and State Parks or Sequoia & Kings Canyon National Parks and to come away with anything but awe at these magnificent organisms. California is special, and we are blessed to have these trees and the places where they grow in our state.