DESCRIPTION OF THE GIANT SEQUOIA
THE GIANT SEQUOIA (Sequoia gigantea [Lindl.] Decn.) and the redwood (Sequoia sempervirens Endl.) are the last surviving species of the rather large genus Sequoia that grew over much of the Northern Hemisphere during ancient geological times. Only two other species of trees closely resemble themthe bald cypress of our Southern States and the cryptomeria of Japan.
The giant sequoia reproduces only from the seeds that older trees rain down annually by the million. In spite of such a generous seed crop, the chances of an individual seed to germinate, survive, and grow into a mature tree are less than one in a billion, owing to the difficult growing conditions created partly by the Sequoias themselves. A deep forest duff, heavy shade, and severe root competition take such a large toll of the relatively few seeds which germinate that it is only those in the most favorable sites that survive the first year or two. For normal growth the sequoia seed must germinate and develop in a continuously moist but well drained soil with plenty of direct sunlight.
Despite the difficulties of growth and the apparent scarcity of seedling sequoias in the groves, the species is in no danger of extinction through lack of reproduction, for whenever fire, wind, or other destructive agents eliminate the older trees and expose the mineral soil large numbers of sequoia seedlings appear and quickly develop into dense stands of vigorous trees. Even in the undisturbed forests one may note occasional seedlings and trees of all ages from youth to veteran.
The sequoia flowers appear in the late winter (February or March) while deep snow is still on the ground. The tiny, bright yellow blossoms burst forth in a solid mass and change the color of the crown from deep green to golden for a short time. Clouds of yellow pollen are released.
The cones are green or brownish in color, egg-shaped, and about 1-1/2 to 2-1/2 inches long and three-fourths to 1 inch in diameter when fully grown, although exceptional specimens may be much larger. They require 2-1/2 years to mature and are formed of approximately 36 hard fibrous scales, each one of which shelters 2 to 6 seeds.
The well-known truth that "mighty oaks from little acorns grow" is less astonishing than that of the sequoias' tiny beginnings. The seeds are flat, about the size of a pinhead, and are enclosed in a scalelike seed case from one-fourth to three-eighths inch long by one-fourth inch wide. They are shed from September on through the fall and winter, although the cones may remain on the branches for many years. Some of the seeds that are not shed immediately may remain fertile in the cones for years, When the cones of the sequoia open, the seed is released, together with tiny flakes of a purplish substance. Dissolved in water, this substance makes a good purple writing fluid.
The sequoia less than 70 years of age sometimes produces a few seeds, but large seed production normally does not occur until the tree is several hundred years old. As long as the tree survives it continues to develop large numbers of cones and fertile seeds. One can merely speculate on the vast numbers of seeds produced by a veteran that has withstood storms, fires, and even geological changes during its life span.
In youth, the sequoia has a tall slender trunk and a thin conical crown, the branches of which cover the trunk nearly to the ground. When the tree reaches its normal maximum height of 250 to 300 feet, it begins to broaden out, develop large lateral limbs, and shed the lower branches. As it reaches old age the sequoia loses its smaller branches and assumes a broad conical or open oval shape with a few immense limbs and large tufts of foliage. Some of the lateral branches of old trees exceed 4 feet in diameterlarger than the trunks of many more familiar trees. The trunks of older trees often show little taper for 100 feet or more above the large buttresses at the base.
The bark of the giant sequoia is one of its most attractive features. It is a beautiful red brown, is of a soft fibrous nature, and is fluted in long vertical plates which give the tree a columnar appearance. The bark near the base of older trees is often from 6 to 10 inches thick, and may even be 2 feet thick. Higher up on the trunk the bark becomes thin, generally not more than 2 inches thick, and has a smooth burnished cast. In younger trees a purplish tinge lends interest to the bark.
The wood of the giant sequoia is distinct from that of other conifers. The sapwood forms a pale yellow narrow band beneath the bark, whereas the heartwood is reddish purple when first exposed, but soon weathers to a dark chocolate brown. The annual growth rings are distinctly visible, except in very old trees where more recent growth may be so slight each year that the rings are almost microscopic in width. Resin canals are lacking, but the wood cells are heavily impregnated with a soluble reddish resinous material.
At one time a considerable volume of lumber was produced from the giant sequoias but, owing to the difficulty of logging such immense trees and the great loss as a result of logging breakage, only a small volume now reaches the market. Although some of the largest trees contain more than 500,000 board feet (enough to build 50 six-room houses), most of this is lost in logging or is of too poor a quality to be economically useful. The small volume still produced is similar to, and is sold as, redwood, but it is coarser grained and generally less satisfactory for most purposes. Its major value is for use where resistance to decay is important but strength is unnecessary. The excellent condition of old fallen logs, some of which fell centuries ago, testifies to the ability of this species to resist decay. It is among the most durable of woods and highly resistant to attack by termites.
One of the characteristics of the older giant sequoias is the frequent occurrence of dead tops. The reason for this phenomenon is not definitely known, but it is unlikely that all of these stag-headed crowns result from any one cause since fire, lightning, loss or interruption of the water supply, deficient soil nutrients, and root injury have been observed to affect individual trees at various times. Many sequoias have been struck by lightning and tops are occasionally burned or broken out, but no sequoia is known to have been killed by lightning. Perhaps many of the dead tops are traceable to partial destruction of the sapwood by fire near the base of the tree, since this portion supplies the channels through which water and minerals from the roots reach the needles, and an interruption of the conduction system may result in serious shortages. Practically all trees with dead tops display large fire scars at their bases. Decreased water and nutrient supplies through changed water courses, increased root competition from other trees, or perhaps a decreasing ability of older root systems to function in a normal manner may account for some of the dead tops.
The evergreen foliage of the giant sequoia consists of scalelike, sharp-pointed leaves closely overlapping each other along the twig, somewhat similar to the junipers. Each bluish-green leaf is about one-half inch long and extends outward from the axis of the stem about one-fourth of an inch. Individual leaves are not shed, but whole twigs and sometimes even branches fall.
The root system of a fallen sequoia is a source of never-ending surprise since the flat plate of closely matted roots is relatively small for such a gigantic trunk. The roots extend out from the trunk in every direction for a hundred feet or more, and the feeding roots are very close to the surface of the ground. The giant sequoia develops no permanent taproot or other roots that extend deep into the ground, but sometimes a single root may grow out near the surface for as much as 200 or 300 feet toward water. It is truly amazing that the shallow and relatively small root systems can support such vast bulks against the storms of the centuries. The trees are nicely balanced, however, and even leaning ones generally have their larger branches concentrated away from the direction of lean. It is interesting to speculate upon the vast quantities of water and minerals that these roots must have supplied to the foliage of one of these veterans through the years. When a tree finally does topple over, the roots are generally broken off close to the base of the tree.
Last Updated: 02-Feb-2007