Trunk in sectional view

Sequoia sempervirens (pronounced /sɨˈkɔɪ.ə sɛmpərˈvaɪrənz/)^[1] is the sole living species of the genus Sequoia in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast redwood, California redwood, and giant redwood. It is an evergreen, long-lived, monoecious tree living 1200–1800 years or more.^[2] This species includes the tallest trees living now on Earth, reaching up to 379 feet (115.5 m) in height (without the roots) and up to 26 feet (7.9 m) in diameter at breast height. Before commercial logging and clearing began by the 1850s, this massive tree occurred naturally in an estimated 2,100,000 acres (8,500 km²) along much of coastal California (excluding southern California where rainfall is not sufficient) and the southwestern corner of coastal Oregon within the United States. An estimated 95% or more of the original old-growth redwood forest has been cut down,^[3] due to its excellent properties for use as lumber in construction.

The name sequoia sometimes refers to the subfamily Sequoioideae, which includes S. sempervirens along with Sequoiadendron (giant sequoia) and Metasequoia (dawn redwood). On its own, the term redwood usually refers to the coast redwood, which is covered in this article, and not to the other two species.

Description

Bark detail

The coast redwood has a conical crown, with horizontal to slightly drooping branches. The bark is very thick, up to 30 cm (12 in), and quite soft and fibrous, with a bright red-brown color when freshly exposed (hence the name redwood), weathering darker. The root system is composed of shallow, wide-spreading lateral roots.

The leaves are variable, being 15–25 mm (0.59–0.98 in) long and flat on young trees and shaded shoots in the lower crown of old trees, and scale-like, 5–10 mm (0.20–0.39 in) long on shoots in full sun in the upper crown of older trees, with a full range of transition between the two extremes. They are dark green above, and with two blue-white stomatal bands below. Leaf arrangement is spiral, but the larger shade leaves are twisted at the base to lie in a flat plane for maximum light capture.

The species is monoecious, with pollen and seed cones on the same plant. The seed cones are ovoid, 15–32 millimetres (0.59–1.3 in) long, with 15–25 spirally arranged scales; pollination is in late winter with maturation about 8–9 months after. Each cone scale bears three to seven seeds, each seed 3–4 millimetres (0.12–0.16 in) long and 0.5 millimetres (0.020 in) broad, with two wings 1 millimetre (0.039 in) wide. The seeds are released when the cone scales dry out and open at maturity. The pollen cones are oval, 4–6 millimetres (0.16–0.24 in) long.

Its genetic makeup is unusual among conifers, being a hexaploid (6n) and possibly allopolyploid (AAAABB).^[4] The mitochondrial genome of the redwood is paternally inherited (unlike that of other conifers).^[5]

Range and ecology

Sunlight shining through redwoods in Muir Woods

Fog is of major importance in coast redwood ecology. Redwood National Park

Coast redwoods occupy a narrow strip of land approximately 750 km (470 mi) in length and 8–75 km (5–47 mi) in width along the Pacific coast of North America; the most southerly grove is in Monterey County, California, and the most northerly groves are in extreme southwestern Oregon. The elevation range is mostly from 30–750 metres (98–2,460 ft) above sea level, occasionally down to 0 and up to 920 m (about 3,000 feet).^[6] They usually grow in the mountains where precipitation from the incoming moisture off the ocean is greater. The tallest and oldest trees are found in deep valleys and gullies, where year-round streams can flow, and fog drip is regular. It was also much harder to get equipment down in these gullies to log them, saving some of the larger specimens. The trees above the fog layer, above about 700 metres (2,300 ft), are shorter and smaller due to the drier, windier, and colder conditions. In addition, tanoak, pine and Douglas-fir often crowd out redwoods at these elevations. Few redwoods grow close to the ocean, due to intense salt spray, sand and wind. Coalescence of coastal fog accounts for a considerable part of the trees' water needs.^[7]

The northern boundary of its range is marked by two groves on the Chetco River on the western fringe of the Klamath Mountains, 25 km (15 mi) north of the California-Oregon border. The largest (and tallest) populations are in Redwood National and State Parks (Del Norte and Humboldt Counties) and Humboldt Redwoods State Park (Humboldt County, California), with the majority located in the much larger Humboldt County. The southern boundary of its range is the Los Padres National Forest's Silver Peak Wilderness in the Santa Lucia Mountains of the Big Sur area of Monterey County, California. The southernmost grove is in the Southern Redwood Botanical Area, just north of the national forest's Salmon Creek trailhead.^[8]

This native area provides a unique environment with heavy seasonal rains (2,500 millimetres (98 in) annually). Cool coastal air and fog drip keep this forest consistently damp year round. Several factors, including the heavy rainfall, create a soil with fewer nutrients than the trees need, causing them to depend heavily on the entire biotic community of the forest, and complete recycling of the trees when dead. This forest community includes coast Douglas-fir, western hemlock, tanoak, Pacific madrone, and other trees, along with a wide variety of ferns, redwood sorrel, mosses and mushrooms. Redwood forests provide habitat for a variety of mammals, birds, reptiles, and amphibians. Old-growth redwood stands provide habitat for the federally threatened spotted owl and the California-endangered marbled murrelet.

The thick, tannin-rich bark, combined with foliage starting high above the ground provides good protection from both fire and insect damage, contributing to the coast redwood's longevity. The oldest known specimen is about 2,200 years old;^[9] many others in the wild exceed 600 years. The numerous claims of older trees are incorrect.^[9] Because of their seemingly timeless lifespans, coast redwoods were deemed the "everlasting redwood" at the turn of the century; in Latin, "sempervirens" means "ever green" or "everlasting". Redwood must endure fire to attain such great ages, so this species has many fire-resistant characteristics. In addition, fires appear to actually benefit redwoods by causing substantial mortality in competing species while having only minor effects on redwood. One recent study, the first to compare postwildfire survival and regeneration of redwood and associated species, concluded fires of all severity increase the relative abundance of redwood and higher-severity fires provide the greatest benefit.^[10]

The prehistoric fossil range of the genus is considerably greater, with a subcosmopolitan distribution including Europe and Asia until about 5 million years ago.

Reproduction

A ring of sequoia trees as seen from below

Coast redwood reproduces both sexually by seed and asexually by sprouting of buds, layering, or lignotubers. Seed production begins at 10–15 years of age, and large seed crops occur frequently, but viability of the seed is low, typically well below 15%.^[11] The low viability may discourage seed predators, which do not want to waste time sorting chaff (empty seeds) from edible seeds. The winged seeds are small and light, weighing 3.3–5.0 mg (200-300 seeds/g; 5,600-8,500/ounce). The wings are not effective for wide dispersal, and seeds are dispersed by wind an average of only 60–120 m (200–400 ft) from the parent tree. Growth of seedlings is very fast, with young trees known to reach 20 m (65 ft) tall in 20 years.

Coast redwoods can also reproduce asexually by layering or sprouting from the root crown, stump, or even fallen branches; if a tree falls over, it will regenerate a row of new trees along the trunk, so many trees naturally grow in a straight line. Sprouts originate from dormant or adventitious buds at or under the surface of the bark. The dormant sprouts are stimulated when the main adult stem gets damaged or starts to die. Many sprouts spontaneously erupt and develop around the circumference of the tree trunk. Within a short period after sprouting, each sprout will develop its own root system, with the dominant sprouts forming a ring of trees around the parent root crown or stump. This ring of trees is called a "fairy ring". Sprouts can achieve heights of 2.3 m (8 ft) in a single growing season.

Redwoods may also reproduce using burls. A burl is a woody lignotuber that commonly appears on a redwood tree below the soil line, though usually within 3 metres (9.8 ft) in depth from the soil surface. Burls are capable of sprouting into new trees when detached from the parent tree, though exactly how this happens is yet to be studied. Shoot clones commonly sprout from burls and are often turned into decorative hedges when found in suburbia.

The species is very tolerant of flooding and flood deposits, the roots rapidly growing into thick silt deposits after floods.

Cultivation and uses

An example of a bonsai redwood, from the Brooklyn Botanic Garden

The Skyline-to-the-Sea Trail passing through a fallen California redwood tree

Coast redwood is one of the most valuable timber species in the lumbering industry. In California, 899,000 acres (3,640 km²) of redwood forest are in production, virtually all of it second growth.^[12] Though many entities have existed in the production and management of redwoods, perhaps none have had a more storied role than the Pacific Lumber Company (1863-2008) of Humboldt County, California, where it owned and managed over 200,000 acres (810 km²) of forests, primarily redwood. Coast redwood lumber is highly valued for its beauty, light weight, and resistance to decay. Its lack of resin makes it resistant to fire.

P. H. Shaughnessy, Chief Engineer of the San Francisco Fire Department wrote:

"In the recent great fire of San Francisco, that began April 18th, 1906, we succeeded in finally stopping it in nearly all directions where the unburned buildings were almost entirely of frame construction and if the exterior finish of these buildings had not been of redwood lumber, I am satisfied that the area of the burned district would have been greatly extended."

Because of its impressive resistance to decay, redwood was extensively used for railroad ties and trestles throughout California. Many of the old ties have been recycled for use in gardens as borders, steps, house beams, etc. Redwood burls are used in the production of table tops, veneers, and turned goods.

The coast redwood is locally naturalized in New Zealand, notably at Whakarewarewa Forest, Rotorua.^[13] Redwood has been grown in New Zealand plantations for over 100 years, and those planted in New Zealand have higher growth rates than those in California, mainly due to even rainfall distribution through the year.^[14] Other areas of successful cultivation outside of the native range include Great Britain, Italy, Portugal,^[15] the Queen Charlotte Islands, middle elevations of Hawaii, Hogsback in South Africa, a small area in central Mexico (Jilotepec) and the southeastern United States from East Texas to Maryland. Coast redwood trees were used in a display at Rockefeller Center and then given to Longhouse Reserve in East Hampton, Long Island, New York and these have now been living there for over 17 years (2010) and survived 2°F (-17°C).^[16]

This fast-growing tree can be grown as an ornamental specimen in those large parks and gardens which can accommodate its massive size. It has gained the Royal Horticultural Society's Award of Garden Merit.^[17]

Statistics

Dried resin of a redwood tree

The foliage of an "albino" Sequoia sempervirens exhibiting lack of chlorophyll

Trees over 200 feet (61 m) are common, and many are over 300 feet (91 m). The current tallest tree is Hyperion, measuring at 379.3 feet (115.6 m).^[9] The tree was discovered in Redwood National Park during the summer of 2006 by Chris Atkins and Michael Taylor, and has been measured as the world's tallest living organism. The previous record holder was the Stratosphere Giant in the Humboldt Redwoods State Park, at 370.18 feet (112.83 m), last measured in 2004 (was 368.57 feet (112.34 m) in Aug 2000 and 369.29 feet (112.56 m) in 2002). Until it fell in March 1991, the "Dyerville Giant" was the record holder. It, too, stood in Humboldt Redwoods State Park; it was 372.05 ft (113.40 m) high and estimated to be 1,600 years old.

Forty-one measured living trees are more than 360 ft (110 m) tall,^[18] and 178 are more than 350 ft (107 m) tall.^[18] Preliminary LiDAR data indicate hundreds of additional trees are in excess of 347.8 ft (106.0 m), which were previously unknown.^[19]

A tree claimed to be 380.12 ft (115.86 m) was cut down in 1914.^[20] A tree claimed to be 424.08 ft (129.26 m) was felled in November 1886 by the Elk River Mill and Lumber Co. at the south fork of Elk River in Humboldt County, yielding 79,736 marketable board feet from 21 cuts.^[21][22][23]

Although coast redwoods are currently the world's tallest trees, the Australian mountain ash and Douglas-fir trees possibly were taller—exceeding 400 feet (120 m)—before the commercial logging of the 19th and 20th centuries. However, fairly solid evidence indicates coast redwoods were the world's largest trees before logging, with specimens measured at over 55,000 cu ft (1,600 m³).^[24]

The theoretical maximum potential height of coast redwoods is limited to between 122 and 130 m (400 and 427 ft), due to gravity and the friction between water and the conduits through which it flows.^[25]

The largest coast redwood is the "Lost Monarch", with an estimated volume of 42,500 cubic feet (1,203 m³); it is 320 ft (98 m) tall, with a diameter of 26 ft (7.9 m) at breast high. It is located in the Grove of Titans. Among current living trees, only six known giant sequoias are larger; these are shorter, but have thicker trunks overall, giving the largest giant sequoia, General Sherman, a volume of 1,487 m³ (52,513 cu ft), making it the world's largest known tree. A redwood cut down in 1926 had a claimed volume of 1,794 m³ (63,355 cu ft), but this was not verified.

About 50 albino redwoods (mutant individuals that cannot manufacture chlorophyll) are known to exist, reaching heights of up to 20 m (66 ft).^[26] These trees survive as parasites, obtaining food by grafting their root systems with those of normal trees, an ability unique to redwoods. While similar mutations occur sporadically in other conifers, no cases are known of such individuals surviving to maturity in any other conifer species.

Largest trees

Redwood with a large burl in Humboldt Redwoods State Park

The 10 largest known coast redwoods by total wood volume in the main trunk and stems combined, as of 2009, are:^[27]

The order of largest and tallest can change at any time due to new discoveries, loss of stem and foliage, growth, and new measurements. One of the better known internet databases for large conifers is the Gymnosperm Database,^[9] but its data can be different from other resources due to differences in standards.

Tallest trees

Trees over 112 m (367 ft), as of 2010:^[18]

See also

• Bank Hall Gardens
• Bury Me in Redwood Country
• Cryptomeria
• Leighton Hall, Powys
• List of largest giant sequoias
• Northern California coastal forests (WWF ecoregion)
• Pacific temperate rain forest (WWF ecoregion)
• Redwood (color)
• Save-the-Redwoods League
• List of superlative trees

References

Further reading

• Preston, Richard. The Wild Trees: A Story of Passion and Daring, Random House, 2007, ISBN 978-1-4000-6489-2.
• Farjon & members of the Conifer Specialist Group (2006). Sequoia sempervirens. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes a lengthy justification of why this species is vulnerable.
• * Noss, R. F., ed. (2000). The Redwood Forest: history, ecology and conservation of the Coast Redwood. Island Press, Washington, D.C. ISBN 1-55963-726-9.