sequoia, name for the redwood (Sequoia sempervirens) and for the big tree, or giant sequoia (Sequoiadendron giganteum), both huge, coniferous evergreen trees of the bald cypress family, and for extinct related species. Sequoias probably originated over 100 million years ago. Once widespread in temperate regions of the Northern Hemisphere, the trees were almost exterminated by the ice sheets of the glacial ages. Several species are known only by fossil remains; some such fossils have been found in the Petrified Forest in Arizona.

The two living species survive only in a narrow strip near the Pacific coast of the United States. The redwood occurs along the coast of California and S Oregon, often in easily lumbered, pure stands. Growing 100 to 385 ft (30-117 m) high, it is probably the tallest tree in the world; the tallest known tree is the redwood Hyperion (379.1 ft/115.5 m), in Redwood National Park. The redwood is able to obtain the abundant moisture needed to sustain its towering growth by capturing water from regularly occurring ocean fogs. The water then drips down from the leaves and branches to the soil, where it penetrates to be absorbed by the roots. The redwood's trunk is 20 to 25 ft (6.1-7.6 m) in diameter, and its needlelike leaves are usually bluish green. Some redwoods are believed to be over 2,000 years old. The big tree, 150 to 325 ft (46-99 m) tall and with a trunk 10 to 30 ft (3-9.1 m) in diameter, grows on the western slopes of the Sierra Nevada in California. It reaches an even greater age than the redwood; some individuals are believed to be 3,000 to 4,000 years old. The leaves are small, overlapping scales. Both trees have deeply grooved, reddish bark and soft, straight-grained, reddish heartwood whose resistance to decay makes it especially valuable for outdoor building purposes, e.g., for shingles, siding, and flumes. Although the sequoias are protected in Kings Canyon, Redwood, Sequoia, and Yosemite national parks, Giant Sequoia National Monument, and several California state parks, their existence elsewhere is threatened by exploitation.

China's deciduous dawn redwood tree (Metasequoia) is believed to be a related species and is perhaps an ancestor of the California redwood. This genus was named and described from fossil remains a few years before the few living specimens were discovered during World War II. Some thousand trees were subsequently found, and they were on the verge of extinction by lumbering. The fast-growing dawn redwoods are now propagated elsewhere. The East Indian and South American redwoods are in the unrelated brazilwood genus.

The sequoia is classified in the division Pinophyta, class Pinopsida, order Coniferales, family Taxodiaceae.

giant sequoia: see sequoia.

Sequoia National Park, 402,510 acres (162,960 hectares), E central Calif.; est. 1890. In the park are 35 groves of giant sequoias, spectacular granite mountains, and deep canyons. The General Sherman Tree, 272 ft (83 m) high and 37 ft (11 m) in diameter at its widest point, is the largest and one of the oldest living things in the world, estimated to be more than 3,500 years old. Within the area are Mt. Whitney, the highest point in the United States outside Alaska; Kern River canyon; and the Great Western Divide, which separates westerly flowing waters from easterly flowing waters. Marble Falls drops 2,000 ft (610 m) in seven cascades. The park adjoins Kings Canyon National Park in the north; the two are administered as a single unit. See National Parks and Monuments, table.

Giant Sequoia National Monument: see National Parks and Monuments (table).

or giant sequoia or Sierra redwood

Coniferous evergreen (Sequoiadendron giganteum; see conifer) found in scattered groves on the western slopes of the Sierra Nevada range of California, U.S. The largest of all trees in bulk, the big tree is distinguished from the coastal redwood (Sequoia sempervirens) by having uniformly scalelike, or awl-shaped, leaves that lie close against the branches, scaleless winter buds, and cones requiring two seasons to mature. The pyramidal tree shape, reddish brown furrowed bark, and drooping branches are common to both genera. The largest specimen (in total bulk) is the General Sherman tree in Sequoia National Park—101.5 ft (31 m) in circumference at its base, 272.4 ft (83 m) tall, and weighing an estimated 6,167 tons (5,593 metric tons). Because big-tree lumber is more brittle than redwood lumber and thus less desirable, the big tree has been easier to preserve; though some groves have been cut, most of the 70 remaining groves are now protected by state or national forests or parks.

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National park, Sierra Nevada range, California, U.S. The park, with an area of 629 sq mi (1,629 sq km), was set aside in 1890 to protect groves of big trees (Sequoiadendron giganteum) that are among the world's largest and oldest living things. The largest tree in the park is thought to be 2,300–2,700 years old. Kings Canyon National Park adjoins Sequoia park to the north; Mount Whitney is on the eastern boundary.

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