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 cones. These cones 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 5-8 thousand feet 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 several hundred to nearly a thousand gallons of water and are therefore often concentrated near drainage areas.
Sequoiadendron giganteum (Giant Sequoia) at Westonbirt Arboretum, Gloucestershire, England
Giant Sequoia tree in the USA, compared with a car. No detail is known of the tree's exact location or name.
Giant Sequoias grow to an average height of 250 to 275 feet (76-84 m) and 15 to 20 feet (5-7 m) in diameter. Record trees have been reported to be 310 feet (95 m) in height and 35 feet (11 m) in diameter. The leaves are awl-shaped and seed cones are 2 to 3 inches (5-8 cm) long and may remain green up to 20 years.
Sequoia bark is fibrous, furrowed, and may be 2 feet (0.6 m) 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 12 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 drys 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 600 feet (183 m) 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 98 to 148 feet (30-40 m).
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 4,590 to 6,560 feet (1,400-2,000 m) in the north, and 5,580 to 7,050 (1,700-2,150 m) 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 35,607 acres (14,416 ha) 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 2,470 acres (1,000 ha) 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. 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
Listing of Largest Giant Sequoia
As of December 2002, the 10 largest sequoia (by volume) are:
| Tree Name | Location | Height (feet) | Circumference (feet) | Volume (cubic feet) |
|---|---|---|---|---|
| General Sherman | Giant Forest | 274.9 | 102.6 | 52,508 |
| Washington | Giant Forest | 254.7 | 101.1 | 47,850 |
| General Grant | Giant Grove | 268.1 | 107.5 | 46,608 |
| President | Giant Forest | 240.9 | 93.0 | 45,148 |
| Lincoln | Giant Forest | 255.8 | 98.3 | 44,471 |
| Stagg | Alder Creek | 243.0 | 109.0 | 42,557 |
| Boole | Converse Basin | 268.8 | 113.0 | 42,472 |
| Genesis | Mountain Home | 253.0 | 85.3 | 41,897 |
| Franklin | Giant Forest | 223.8 | 94.8 | 41,280 |
| King Arthur | Garfield | 270.3 | 104.2 | 40,656 |