Sequoiadendron giganteum (Giant Sequoia, Sierra Redwood, or Wellingtonia) is the sole species in the genus Sequoiadendron, and one of three species of coniferous trees known as redwoods, classified in the family Cupressaceae in the subfamily Sequoioideae, together with Sequoia sempervirens (Coast Redwood) and Metasequoia glyptostroboides (Dawn Redwood). The common names "sequoia" and "redwood" generally refer to Sequoiadendron and the coast redwood, respectively.
Giant Sequoias are the world's largest trees in terms of total volume (technically, only 6 living Giant Sequoia exceed the of the Lost Monarch Coast Redwood tree; see Largest trees). They grow to an average height of 50-85 m (165-280 ft) and 6-8 m (18-24 ft) in diameter. Record trees have been measured to be 94.8 m (311 ft) in height and 17 m (57 ft) in diameter. The oldest known Giant Sequoia based on ring count is 3,500 years old. Sequoia bark is fibrous, furrowed, and may be 90 cm (3 ft) thick at the base of the columnar trunk. It provides significant fire protection for the trees. The leaves are evergreen, awl-shaped, 3-6 mm long, and arranged spirally on the shoots. The seed cones are 4-7 cm long and mature in 18-20 months, though they typically remain green and closed for up to 20 years; each cone has 30-50 spirally arranged scales, with several seeds on each scale giving an average of 230 seeds per cone. The seed is dark brown, 4-5 mm long and 1 mm broad, with a 1 mm wide yellow-brown wing along each side. Some seed is shed when the cone scales shrink during hot weather in late summer, but most seeds are liberated when the cone dries out from fire heat and/or insect damage (see Ecology, below).
Giant Sequoia regenerates by seed. Trees up to about 20 years old may produce stump sprouts subsequent to injury. Giant Sequoia of all ages may sprout from the bole when old branches are lost to fire or breakage, but (unlike Coast Redwood) mature trees do not sprout from cut stumps. Young trees start to bear cones at the age of 12 years.
At any given time, a large tree may be expected to have approximately 11,000 cones. The upper part of the crown of any mature Giant Sequoia invariably produces a greater abundance of cones than its lower portions. A mature Giant Sequoia has been estimated to disperse from 300,000-400,000 seeds per year. The winged seeds may be carried up to 180m (600 ft) from the parent tree.
Lower branches die fairly readily from shading, but trees less than 100 years old retain most of their dead branches. Trunks of mature trees in groves are generally free of branches to a height of 20-50 m, but solitary trees will retain low branches.
Giant Sequoia is usually found in a humid climate characterized by dry summers and snowy winters. Most Giant Sequoia groves are on granitic-based residual and alluvial soils. The elevation of the Giant Sequoia groves generally ranges from 1,400-2,000 m (4,600-6,600 ft) in the north, and 1,700-2,150 m (5,600-7,000 ft) to the south. Giant Sequoia generally occurs on the south facing side of northern mountains, and on the northern face of more southern slopes.
High levels of reproduction are not necessary to maintain the present population levels. Few groves, however, have sufficient young trees to maintain the present density of mature Giant Sequoias for the future. The majority of Giant Sequoias are currently undergoing a gradual decline in density since the European settlement days.
The Giant Sequoias are having difficulty reproducing in their original habitat (and very rarely reproduce in cultivation) due to the seeds only being able to grow successfully in mineral soils in full sunlight, free from competing vegetation. Although the seeds can germinate in moist needle humus in the spring, these seedlings will die as the duff dries in the summer. They therefore require periodic wildfire to clear competing vegetation and soil humus before successful regeneration can occur. Without fire, shade-loving species will crowd out young sequoia seedlings, and sequoia seeds will not germinate. When full grown, these trees typically require large amounts of water and are therefore often concentrated near streams.
Fires also bring hot air high into the canopy via convection, which in turn dries and opens the cones. The subsequent release of large quantities of seeds coincides with the optimal post-fire seedbed conditions. Loose ground ash may also act as a cover to protect the fallen seeds from ultraviolet radiation damage.
Due to fire suppression efforts and livestock grazing during the early and mid 20th century, low-intensity fires no longer occurred naturally in many groves, and still do not occur in some groves today. The suppression of fires also led to ground fuel build-up and the dense growth of fire-sensitive White Fir. This increased the risk of more intense fires that can use the firs as ladders to threaten mature Giant Sequoia crowns. Natural fires may also be important in keeping carpenter ants in check.
In 1970 the National Park Service began controlled burns of its groves to correct these problems. Current policies also allow natural fires to burn. One of these untamed burns severely damaged the second-largest tree in the world, the Washington tree, in September 2003, 45 days after the fire started. This damage made it unable to withstand the snowstorm of January 2005, leading to the collapse of over half the trunk.
In addition to fire, there are also two animal agents for Giant Sequoia seed release. The more significant of the two is a longhorn beetle (Phymatodes nitidus) that lays eggs on the cones, into which the larvae then bore holes. This cuts the vascular water supply to the cone scales, allowing the cones to dry and open for the seeds to fall. Cones damaged by the beetles during the summer will slowly open over the next several months. Some research indicates that many cones, particularly higher in the crowns, may need to be partially dried by beetle damage before fire can fully open them. The other agent is the Douglas Squirrel (Tamiasciurus douglasi) that gnaws on the fleshy green scales of younger cones. The squirrels are active year round, and some seeds are dislodged and dropped as the cone is eaten.
The first reference to the Giant Sequoia by Europeans is in 1833, in the diary of the explorer J. K. Leonard; the reference does not mention any locality, but his route would have taken him through the Calaveras Grove. This discovery was not publicized. The next European to see the species was John M. Wooster, who carved his initials in the bark of the 'Hercules' tree in the Calaveras Grove in 1850; again, this received no publicity. Much more publicity was given to the "discovery" by Augustus T. Dowd of the Calaveras Grove in 1852, and this is commonly cited as the species' discovery. The tree found by Dowd, christened the 'Discovery Tree', was felled in 1853.
The first scientific naming of the species was by John Lindley in 1853, who named it Wellingtonia gigantea, without realizing this was an invalid name under the botanical code as the name Wellingtonia had already been used earlier for another unrelated plant (Wellingtonia arnottiana in the family Sabiaceae). The name "Wellingtonia" has persisted in England as a common name, though is deprecated as cultural imperialism (R. Ornduff in Aune 1994). The following year, Joseph Decaisne transferred it to the same genus as the Coast Redwood, naming it Sequoia gigantea, but again this name was invalid, having been applied earlier (in 1847, by Endlicher) to the Coast Redwood. The name Washingtonia californica was also applied to it by Winslow in 1854, though this too is invalid, belonging to the palm genus Washingtonia.
In 1907 it was placed by Carl Ernst Otto Kuntze in the otherwise fossil genus Steinhauera, but doubt as to whether the Giant Sequoia is related to the fossil originally so named makes this name invalid.
The nomenclatural oversights were finally corrected in 1939 by J. Buchholz, who also pointed out that the Giant Sequoia is distinct from the Coast Redwood at the genus level and coined the name Sequoiadendron giganteum for it.
John Muir wrote of the species in about 1870:
As of 2002 (updated to remove Washington tree, previously in second place), the largest Giant Sequoias by volume are:
|Rank||Tree Name||Grove||Height||Girth at Ground||Volume|
|1||General Sherman||Giant Forest||84.2||274.9||33.0||109.0||1487||52,508|
|2||General Grant||Grant Grove||82.0||268.1||33.5||107.5||1320||46,608|
|5||Stagg||Alder Creek Grove||74.1||243.0||33.2||109.0||1205||42,557|
|6||Boole Tree||Converse Basin||81.9||268.8||34.8||113.0||1205||42,509|
|7||Genesis||Mountain Home Grove||78.5||253.0||26.0||85.3||1186||41,900|
|9||King Arthur||Garfield Grove||82.4||270.3||31.8||104.2||1151||40,656|
|11||Robert E. Lee||Grant Grove||77.6||254.7||26.8||88.0||1135||40,102|
|13||Ishi Giant||Kennedy Grove||77.7||255.0||32.1||105.4||1080||38,156|
|14||Column Tree||Giant Forest||74.3||244.0||28.4||93.0||1064||37,595|
|15||Summit Road Tree||Mountain Home Grove||74.4||244.0||25.1||82.2||1036||36,600|
|16||Euclid||Mountain Home Grove||83.1||272.7||25.4||83.4||1023||36,122|
|18||General Pershing||Giant Forest||75.0||246.0||27.8||91.2||1015||35,855|
|19||Diamond Tree||Atwell Mill Grove||87.2||286.0||29.1||95.3||1000||35,292|
|20||Adam||Mountain Home Grove||75.4||247.4||28.71||94.2||991||35,017|
|21||Roosevelt||Redwood Mountain Grove||80.0||260.0||24.4||80.0||991||35,013|
|23||AD||Atwell Mill Grove||73.9||242.5||30.2||99.0||983||34,706|
|24||Hart||Redwood Mountain Grove||84.8||288.0||23.0||75.4||974||34,407|
|25||Grizzly Giant||Mariposa Grove||63.8||210.0||28.2||92.5||963||34,005|
|26||Chief Sequoyah||Giant Forest||70.0||228.5||27.6||90.4||952||33,608|
|27||Methuselah||Mountain Home Grove||63.4||207.8||29.3||96.0||934||32,900|
|28||Great Goshawk||Freeman Creek||77.8||255.2||27.5||90.2||928||32,783|
|30||Dean||Atwell Mill Grove||71.9||235.9||29.4||96.4||915||32,333|
|31||Black Mountain beauty||Black Mountain Grove||80.2||263.0||23.1||76.0||912||32,224|
|32||Packsaddle Giant||Packsaddle Grove||66.5||219.0||32.5||106.4||910||32,156|
|33||Allen Russel||Mountain Home Grove||77.4||254.1||24.4||80.2||900||31,650|
|36||Agassiz||Calaveras Big Trees State Park||80.0||262.0||30.1||98.0||866||30,580|
|37||Near Ed By Ned||Giant Forest||76.5||251.0||24.2||79.5||859||30,333|
|38||Evans Tree||Kennedy Grove||70.9||232.4||23.7||77.5||856||30,232|
|39||Three Fingered Jack||Mountain Home Grove||73.2||240.0||25.2||82.5||853||30,118|
|41||Red Chief||Long Meadow Grove||74.7||245.0||24.6||80.6||813||28,723|
|42||Bull Buck||Nelder Grove||75.1||246.1||30.2||99.1||775||27,383|
|43||Near Gutless||McIntyre Grove||77.3||252.1||23.2||75.6||757||26,737|
|44||Gutless Goliath||McIntyre Grove||83.9||275.1||20.7||68.0||752||26,564|
|46||Bannister's Tree||Freeman Creek||59.4||195||31.5||103.5||731||26,100|
|47||Ghost Tree||Packsaddle Grove||55.1||180.6||28.9||95.0||709||25,047|
Source: The volume figures have a low degree of accuracy (at best about ±14m³), due to difficulties in measurement; stem diameter measurements are taken at a few set heights up the trunk, and assume that the trunk is circular in cross-section, and that taper between measurement points is even. The volume measurements also do not take cavities into account. The measurements are trunk-only, and do not include the volume of wood in the branches or roots.
The General Sherman tree is estimated to weigh about 2100 tonnes (Fry & White 1938).
Greatest Base Diameter
Greatest Mean Diameter at Breast Height
Wood from mature Giant Sequoias is highly resistant to decay, but is fibrous and brittle, making it generally unsuitable for construction. From the 1880s through the 1920s logging took place in many groves in spite of marginal commercial returns. Due to their weight and brittleness trees would often shatter when they hit the ground, wasting much of the wood. Loggers attempted to cushion the impact by digging trenches and filling them with branches. Still, it is estimated that as little as 50 percent of the timber made it from groves to the mill. The wood was used mainly for shingles and fence posts, or even for matchsticks.
Pictures of the once majestic trees broken and abandoned in formerly pristine groves, and the thought of the giants put to such modest use, spurred the public outcry that caused most of the groves to be preserved as protected land. The public can visit an example of 1880s clear-cutting at Big Stump Grove near Grant Grove. As late as the 1980s some immature trees were logged in Sequoia National Forest, publicity of which helped lead to the creation of Giant Sequoia National Monument.
The wood from immature trees is less brittle, with recent tests on young plantation-grown trees showing it similar to Coast Redwood wood in quality. This is resulting in some interest in cultivating Giant Sequoia as a very high-yielding timber crop tree, both in California and also in parts of western Europe, where it may grow more efficiently than Coast Redwoods. In the northwest United States some entrepreneurs have also begun growing Giant Sequoias for Christmas trees. Besides these attempts at tree farming, the principal economic uses for Giant Sequoia today are tourism and horticulture (see Cultivation, below).
Giant Sequoia is a very popular ornamental tree in many areas. Areas where it is successfully grown include most of western and southern Europe, the Pacific Northwest of North America north to southwest British Columbia, southeast Australia, New Zealand and central-southern Chile. It is also grown, though less successfully, in parts of eastern North America.
Sequoiadendron has been successfully planted in the British Isles, parts of continental Europe, as well as in much of the western, southern, and eastern USA. Trees can withstand temperatures of -31 °C (-25 °F) or colder, for short periods of time providing the ground around the roots is insulated with either heavy snow or mulch. Outside its natural range, sequoia's foliage suffers from damaging windburn. Large specimen examples grow in arboretums in Pennsylvania and Rhode Island USA. A large sequoia, planted by horticulturist Claude Heit in the 1960s, is growing in the Finger Lakes region of New York USA. An experimental private planting of young sequoia trees (less than 5 years old in early 2007) exists in Vermont USA. In Washington and Oregon, it is common to find giant sequoias that have been successfully planted in both urban and rural areas. In the Seattle area, large specimens (over 90 feet) are fairly common and exist in several city parks and many private yards (especially east Seattle including Capitol Hill, Washington Park, & Leschi/Madrona). Additionally, Coast Redwoods can be seen in Lincoln Park and on the University of Washington campus.
The limit of winter cold tolerance is generally down to about −30 °C, but with a few individuals known to have tolerated lower temperatures, particularly where they benefit from deep snow cover over the roots.
Since its discovery a wide range of horticultural varieties have been selected, especially in Europe. There are, amongst others, weeping, variegated, pygmy, blue, grass green, and compact forms .
Growth in Britain is very fast, with the tallest tree, at Benmore in southwest Scotland, reaching 54 m (177 ft) at age 150 years, and several others from 50-53 m tall; the stoutest is around 12 m in girth and 4 m in diameter, in Perthshire. The Royal Botanic Gardens at Kew in London also contains a large specimen.
Growth rates in some areas are remarkable; one young tree in Italy reached 22 m (72.18 ft) tall and 88 cm (2.89 ft) trunk diameter in 17 years (Mitchell, 1972).
Giant sequoias have also been planted in Belgium, the Netherlands and Luxembourg. The stoutest one has a diameter of 2.83 m (9.28 ft).
Growth further northeast in Europe is limited by winter cold. In Denmark, where extreme winters can reach −32 °C, the largest tree was 35 m (114.83 ft) tall and 1.7 m (5.58 ft) diameter in 1976 and is bigger today. One in Poland has purportedly survived temperatures down to −37 °C with heavy snow cover.
In the northeastern USA there has been some limited success in growing the species, but growth is much slower there, and it is prone to Cercospora and Kabatina fungal diseases due to the hot, humid summer climate there. A tree at Blithewold Gardens, in Bristol, Rhode Island is reported to be 27 meters (90 ft) tall, reportedly the tallest in the New England states. The tree at the Tyler Arboretum in Delaware County, Pennsylvania at 29.1 m (95.4 ft) may be the tallest in the northeast. Specimens also grow in the Arnold Arboretum in Boston, Massachusetts (planted 1972, 18 m tall in 1998), at the Longwood Gardens near Wilmington, Delaware, and in the Finger Lakes region of New York for many years. Private plantings of Giant Sequoias around the Middle Atlantic States are not uncommon. Since 2000, a small amateur experimental planting has been underway in the Lake Champlain valley of Vermont at the Vermont Experimental Cold-Hardy Cactus Garden where winter temperatures can reach −37 °C with variable snowcover.
A cold-tolerant cultivar 'Hazel Smith' selected in about 1960 is proving more successful in the northeastern U.S.A. This clone was the sole survivor of several hundred seedlings grown at a nursery in New Jersey.