Sequoiadendron giganteum

Sequoiadendron giganteum (giant sequoia, Sierra redwood, Sierran redwood, or Wellingtonia, is the only living member of the Sequoiadendron genus, and one of only three conifers known as redwoods, with the other two being Sequoia sempervirens and Metasequoia glyptostroboides. The name "sequoia" usually refers to Sequoiadendron giganteum, which is naturally found only in groves on the western slopes of the Sierra Nevada in California.

Description
The giant sequoia is the world's largest organism by volume (only 7 exceed 42,500 ft3.) They grow between 165 and 280 feet tall but have reached up to 311 feet, and 18-24 feet in diameter. The oldest known sequoia has been said to be about 3,500 years old due to ring count. The bark of the giant sequoia may be 3 feet thick at the bottom of the trunk. The leaves are 3-6 mm long. Its seed cones are 4-7 cm long, and and mature between 18 and 20 months. They are colored green until about 20 years. There is an average of 230 seeds per cone. The seeds are brown, 4-5 mm long.

The giant sequoia regenerates by a seed, like every other spermatophyte plant. All ages of the giant sequoia sprout from its bole when older branches are lost. Young trees bear cones at about 12 years old.

At any time, a large tree may bear 11,000 cones. A mature sequoia is expected to disperse 300,000 to 400,000 seeds a year. The seeds can be carried anywhere between 0 and 600 feet from the tree.

Distribution
The natural habitat of the giant sequoia is west of the Sierra Nevada, in California of the United States. They occur in scattered groves, comprising an area of 14,416 hectares. Two-thirds of the sequoias are from the American River in Placer County to the Kings River. The remaining sequoias are located between the Kings River and Deer Creek Grove.

It is usually found in a humid climate that alternates between seasons that have dry summers and snowy winters. The elevation in which Sequoiadendron giganteum lives are between 4,600-6,600 feet above sea level.

These large trees are also distributed throughout the world as cultivars. See cultivation.

Ecology
It is hard for the giant sequoias to reproduce where they live originally, due to the seeds only being able to grow in mineral soil, and in full sunlight. Though the seeds are able to germinate in humus in the spring, they will die in the summer. They require wildfires to clear any competing vegitation, so that the trees will grow. Without wildfires, plants that enjoy the shade of the sequoia will wipe off the seedlings. When fully grown, these trees need a large amount of water, which is why sequoias are often times located near streams.

The fires will bring hot air high into the tree canopy, thus drying and opening the cones.

Although fire is a main way that seeds are dispersed from the pine cones, two animals help also. The longhorn beetle (Phymatodes nitidus) lays eggs on the cone. When these eggs hatch, the newly born larvae will bore holes, allowing the cones to dry, and release the seeds. The other animal agent is the Douglas Squirrel. It gnaws on the young cones, and some seeds drop in the process.

Discovery and naming
The giant sequoia was known by the Native American tribes that lived in the area, naming it Wawona, Toos-pung-ish and Hea-mi-withic.

The first reference to European people was in 1833, in J.K. Leonard's diary. This journal wasn't publicized, so the next European who noticed it John M. Wooster carved his initials in the 'Hercules' sequoia, given no publicity once again. Publicity was finally given when Augustus T. Dowd "discovered" it.

John Lindley finally gave the sequoia a scientific name in 1853, naming it Wellingtonia gigantea. This name, however was incorrect under the International Code of Botanical Nomenclature, because Wellingtonia was already used for a plant that wasn't related to S. giganteum (Wellingtonia arnottiana). The following year, Joseph Decaisne named the tree Sequoia gigantea, which was also invalid, being earlier applied to the Coast Redwood. Winslow later applied the name, Washingtonia californica to the tree, but was yet again invalid, given to a genus of palms.

In 1907, Carl Ernst Otto Kuntze placed the species into the extinct genus, Steinhauera, but doubt to the fact that they were related caused the name to be invalid.

John T. Buchholz finally corrected the naming in 1939, saying that the Coast Redwood and giant sequoia were distinct by genus, so he named it, Sequoiadendron giganteum.

Uses
The wood from mature sequoias is resistant to decay, but is fibrous and brittle, making it not used for construction. Between the 1880's and 1920's, these trees were logged, but would often shatter when they hit the ground, leaving only some of the wood usable. Loggers tried to soften the landing with branches in a trench, but less than 50 percent ever was brought back. The wood was used for shingles, fence posts, and matchsticks.

The wood of immature trees is less brittle, which stirred people into forming cultivars of the tree for the timber.

Cultivation
The tree is a popular ornamental tree in some areas, successfully grown in parts of Europe, the United States, Australia, New Zealand, and coastal Chile. The tree has been planted successfully in the British Isles, along with several parts in the United States. It can withstand from -25 °F for short periods of time.

Europe
The Giant Sequoia was first cultivated in 1853 by Scottish, John D. Matthew, who obtained seeds from Calaveras Grove. A much larger shipment was collected by William Lobb yet again in the same year.

In the United Kingdom, the tree grows much faster than it does anywhere else, reaching 177 feet in 150 years. The Royal Botanical Gardens in Kew contains a very large specimen.

One tree in Italy grew very remarkable, growing 72.18 feet tall and 2.89 feet in diameter by in only 17 years.

Growth in northeast Europe is limited by the lack of heat. In Denmark, the largest tree was 114.83 feet tall, and 5.58 feet in diameter in 1976.

United States and Canada
Giant Sequoia cultivation is successful from western Oregon up to British Colombia, where the trees grow at fast rates.

In the United States, there is limited success, because growth is much slower there, and during the hot, humid, summer climate, the tree is prone to Cercospora and Kabatina fungal diseases. A tree in Rhode Island is reported to be 90 feet tall, the tallest in the New England states. There are several specimens in places, such as Boston, Massachusetts (18 meters in 1998), Wilmington, Delaware, and the Finger Lakes region of New York. These plants have been planted privately in Middle-Atlantic states very commonly.

A cultivar created in 1960, the Sequoiadendron giganteum 'Hazel Smith', is tolerant to the cold weather, and proves to be more successful in the northeastern U.S.

Australia
The Ballarat Botanical Gardens in Australia has a significant collections of the giant sequoia, most of which are over 150 years old. Several parks have specimens as well. In Tasmania, specimens are found in private and public gardens, very popular during the Victorian era.

New Zealand
Several interesting specimens of the giant sequoia are found on the South Island of New Zealand. Some of these are in a public park in Picton, and in the gardens, public and private, in Queenstown.

Largest
As of 2009, the largest sequoias (all of which are in California) by volume are:

Giant sequoia superlatives
Largest
 * General Sherman - Giant Forest - 52,508 cubic feet

Tallest
 * Unnamed tree - Redwood Mountain Grove - 311 feet tall

Oldest
 * Examples from the Converse basin, Mountain home grove, and Giant forest - 3,500 years or more

Largest Girth
 * Waterfall Tree - Alder Creek Grove - 155 ft.

Greatest Base Diameter
 * Waterfall Tree - Alder Creek Grove - 57 feet
 * Tunnel Tree - Atwell Mill Grove - 57 feet

Greatest Mean Diameter at Breast Height
 * General Grant - General Grant Grove - 29 feet

Largest Limb
 * Arm Tree - Atwell Mill, East Fork Grove - 12.8 feet in diameter

Thickest Bark
 * 3 feet or more