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| Giant Sequoia | ||||||||||||||
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 General Grant tree in Sequoia National Park | ||||||||||||||
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| Sequoiadendron giganteum |
The Giant Sequoia or Giant Redwood (Sequoiadendron giganteum) is one of a number of species of gymnosperm tree known as redwoods, classified in the Family Cupressaceae (in a part of this family formerly segregated as Taxodiaceae). Even though these trees are among the tallest in the world they have some of the smallest seeds. These seeds can only germinate in mineral soils and possibly only soils derived from metamorphic rock. Periodic fire, large amounts of water, and the climatic conditions that exist at 1,500-2,400 m altitude in the Sierra Nevada are vital conditions for sequoia. Without fire, shade-loving species will crowd out young sequoia and sequoia seeds will not germinate. When full grown, these trees typically require large amounts of water and are therefore often concentrated near streams.
Giant Sequoias grow to an average height of 76-84 m (250-275 feet) and 5-7 m (15-20 feet) in diameter. Record trees have been reported to be 93 m (305 feet) in height and 11 m (35 feet) in diameter. The leaves are awl-shaped, 3-6 mm long. The seed cones are 4-7 cm long and may remain green up to 20 years.
Sequoia bark is fibrous, furrowed, and may be 60 cm (2 feet) thick at the base of the columnar trunk. The oldest known Giant Sequoia based on ring count is 3,200 years old.
Giant Sequoia regenerates primarily by seed, although occasionally it may reproduce naturally by vegetative methods. Giant Sequoias up to about 20 years of age 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. Young trees start to bear cones at the age of 20 years. Cones may remain attached to the tree for 8 to 20 years and much of the seed will be retained. During the late summer, however, some seed is shed when the cone scales shrink. Most seeds are liberated when the cone dries out and becomes detached. Each cone yields an average of 230 seeds.
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 to 400,000 seeds per year. The winged seeds may be carried up to 180 m (600 feet) from the parent tree.
Giant Sequoia is the world's largest tree in terms of total volume. Lower branches die fairly readily from shading, but trees less than 100 years old retain most of their dead branches. Boles of mature trees generally are free of branches to a height of 30-40 m (100-150 feet).
Giant Sequoia is found in a humid climate characterized by dry summers. 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 feet) in the north, and 1,700-2,150 m (5,600 to 7,000) to the south. Giant Sequoia generally appears on southern slopes in its northern distribution and on more northerly slopes in the south.
The natural distribution of Giant Sequoia is restricted to about 75 groves, comprising a total area of only 14,416 ha (35,607 acres) along a limited area of the western Sierra Nevada, California. The northern two-thirds of its range, from the American River in Placer County southward to the Kings River has only eight disjunct groves.
The remaining groves are concentrated between the Kings River and the Deer Creek Grove in southern Tulare County. Groves range in size from approximately 1,000 ha (2,500 acres) with 20,000 giant sequioas to small groves with only six living trees.
Giant Sequoia principally occurs in scattered groves. Nowhere does it grow in pure stands, although in a few small areas stands do approach a pure condition . 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. Sequoia seeds germinate and grow best in open mineral soils with minimal forest litter. Such soils are produced by low-intensity ground fires. Furthermore, Giant Sequoia are more likely to release seeds due to hot air caused by a fire. Due to fire suppression efforts and livestock grazing during the 20th Century, low-intensity fires do not naturally occur. class="external">[1
Giant sequoia in cultivation
Giant sequoia is a popular ornamental tree in many areas. It was first brought into cultivation in 1853, when a large shipment of seed arrived in Britain. Growth in Britain is very fast, with the tallest tree, at Benmore in southwest Scotland, reaching 54m at age 150 years (Tree register of the British Isles), and several others from 50-53m tall; the stoutest is 3.55m diameter, in Perthshire. Other areas where it is successfully grown include most of western Europe, the Pacific Northwest of North America north to at least Vancouver, southeast Australia, New Zealand and central-southern Chile. Growth rates in some areas are remarkable; one young tree in Italy reached 22m tall and 88 cm trunk diameter in 17 years.
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 humid summer climate there. The tallest reported in the east is one just over 30m tall, at Manistee in Michigan. A recently selected disease-resistant and cold tolerant cultivar 'Hazel Smith' is proving more successful in that area. This clone was the sole survivor of several thousand seedlings grown at a nursery in New Jersey.
As of December 2002, the 10 largest sequoia (by volume) are:
Listing of Largest Giant Sequoia
| Tree Name | Location | Height | Circumference | Volume | |||
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| (meters) | (feet) | (meters) | (feet) | (meters3) | (feet3) | ||
| General Sherman | Giant Forest | 83.79 | 274.9 | 31.27 | 102.6 | 1486.9 | 52,508 |
| Washington | Giant Forest | 77.63 | 254.7 | 30.82 | 101.1 | 1355.0 | 47,850 |
| General Grant | Giant Grove | 81.72 | 268.1 | 32.77 | 107.5 | 1319.8 | 46,608 |
| President | Giant Forest | 73.43 | 240.9 | 28.35 | 93.0 | 1278.4 | 45,148 |
| Lincoln | Giant Forest | 77.97 | 255.8 | 29.96 | 98.3 | 1259.3 | 44,471 |
| Stagg | Alder Creek | 74.07 | 243.0 | 33.22 | 109.0 | 1205.0 | 42,557 |
| Boole | Converse Basin | 81.93 | 268.8 | 34.44 | 113.0 | 1202.7 | 42,472 |
| Genesis | Mountain Home | 77.11 | 253.0 | 26.00 | 85.3 | 1186.4 | 41,897 |
| Franklin | Giant Forest | 68.21 | 223.8 | 28.90 | 94.8 | 1168.9 | 41,280 |
| King Arthur | Garfield | 82.39 | 270.3 | 31.76 | 104.2 | 1151.2 | 40,656 |
