Many economically important species belong to the taxodium family, including cultivated ornamentals and timber trees. They are dominant trees in several ecosystems, including temperate forests and swamps. Most of the species are evergreen, but some are deciduous and drop their leaves during the fall months. In addition, the most massive and tallest trees in the world belong to this remarkable plant family. Abundant fossil evidence of these magnificent trees dating back more than 100 million years has been found in north America. Some of today's species look remarkable similar to fossilized trees that lived when dinosaurs walked on the earth.

Prior to the discovery of ancient bristlecone pines and creosote bush rings, the world's record for longevity went to the magnificent giant sequoia (Sequoiadendron giganteum) of the western slopes of the Sierra Nevada. The greatest authenticated age of a giant sequoia, derived from counting annual rings on a cut stump, was nearly 3,200 years. Several specimen trees of Fitzroya cupressoides, a related conifer in southern Chile and Argentina, are more than 3,500 years old. Although it may fall short of the world's oldest, the giant sequoia has the undisputed record for the world's most massive living thing. The largest tree, named General Sherman, is 275 feet tall with a massive trunk 35 feet in diameter and 102 feet in circumference at the base. Even more remarkable is the fact that at a point 120 feet in the air the trunk of General Sherman is still 17 feet in diameter. It has been estimated to contain over 600,000 board feet of timber, enough to build 120 average-sized houses. In fact, a single giant sequoia may contain more wood than is found on several acres of some of the finest virgin timberland in the Pacific Northwest. The trunk of General Sherman alone weighs nearly 1400 tons. By way of comparison, this is roughly equivalent to 15 adult blue whales, 8 diesel-electric train locomotives, or 20 M-60 battle tanks. It is quite remarkable when you realize that this enormous tree started out about 2,000 years ago as a tiny embryo with a seed only 1/4 of an inch (6 mm) long.

Another conifer species called the Montezuma bald cypress (Taxodium mucronatum) occasionally grows into a huge tree. One enormous specimen of this tree grows in the churchyard of Santa Maria de Tule near Oaxaca, Mexico. Called "El Gigante" by the locals, it is one of the most massive of all living things, with a trunk circumference of nearly 118 feet (36 m), larger than the General Sherman giant sequoia. If the perimeter measurement includes the bays and prominences of the buttressed trunk, the circumference exceeds 150 feet (46 m). With a diameter greater than 40 feet (12 m), the trunk of this spectacular tree is literally the size of a house. This gigantic tree was once thought to be 10,000 years old, but botanists now consider it to be a youngster of only 1,500 to 2,000 years. Scientists once thought "El Gigante" was multiple trunks fused together, but recent DNA evidence indicates that this is indeed a single individual.

The world's record for the tallest tree goes to another cone-bearing tree native to California, the coast redwood (Sequoia sempervirens). In fact, this is the state tree of California. The tallest living redwood on record stands 379 feet (116 m), 64 feet (20 m) taller than the Statue of Liberty (from the base to the torch). Redwoods are native to a narrow strip of land (fog belt) from southern Monterey County to the southwestern corner of Oregon. Only about 15 percent of the redwood forests are protected within state and national parks. California redwoods are rivaled in size by the amazing flowering Australian tree (Eucalyptus regnans). The record for the tallest tree of all time has been debated by botanists for centuries. Some amazing claims for towering Douglas fir (Pseudotsuga menziesii) and E. regnans exceeding 400 feet (122 m) have never been substantiated by a qualified surveyor. In 1872, a fallen E. regnans 18 feet (5.5 m) in diameter and 435 feet (132 m) tall was reported by William Ferguson, making it the tallest (or perhaps longest) dead tree. According to the monograph on Eucalyptus by Stan Kelly (Volume 1 of Eucalypts, 1977), trees of E. regnans well over 300 feet (91 m) tall have been measured, but the tallest tree known to be standing at present is 322 feet (98 m). The redwood shown in the left image is over 250 feet tall (76 m), roughly twice the height of the tallest tree in San Diego County.

California redwoods are named for the color of their bark and heartwood. The high tannin content imparts the reddish coloration and gives the wood a remarkable resistance to fungal rot and insect infestations. The thick, fibrous bark has an even higher tannin content, and insulates the inner cambium layer from occasional natural fires. Giant sequoias of the Sierra Nevada have similar red heartwood and fire-resistant bark. Fire-scarred trunks on old patriarch trees are evidence that they survived many fires during the past 20 or 30 centuries.

Redwoods and giant sequoias were once classified in the same genus Sequoia. In 1939 botanist J.T. Buchholz placed the giant sequoia in its present genus of Sequoiadendron. There are a number of substantial taxonomic differences between the two species, including their chromosome numbers. The giant sequoia has a diploid number of 22 with two sets of chromosomes, while redwoods have a hexaploid number of 66 with six sets of chromosomes. In addition, redwoods commonly sprout from adventitious buds in their root crowns. Cut stumps can resprout at any season of the year within one month. Botanists have theorized that redwoods originated from hybridization between a Metasequoia and another extinct conifer during the late Mesozoic era (70-120 million years ago).

Approximately three million years ago, redwoods (Sequoia sempervirens) in the coast ranges of northern California (west of present-day Calistoga) were leveled by a powerful volcanic eruption from the direction of Mt. St. Helena seven miles (11.3 km) to the northeast. The blast knocked the trees down and covered them with volcanic ash. Over the centuries, woody tissue in the trees was permeated by water-laden silicates. The hollow xylem cells were gradually replaced with crystalized silica until the entire trees were converted into stone. The petrified wood also contains veins of quartz or druzy quartz which gives the wood a sparkly appearance. Unlike petrified trees of other regions, the trees are light-colored due to the sandy, creamy-white ash. At the time of their deaths, the largest trees were nearly 2,000 years old. [During the Mt. St. Helens eruption in southern Washington in 1980, most of the conifers were knocked down but not buried, so they will not be petrified.]

The "Petrified Forest" west of Calistoga was discovered in 1870 by Charles Evans, known as "Petrified Charlie." It is privately owned and is a California Registered Historical Landmark. This is certainly one of California's little-known natural wonders, and a very rewarding field trip.

Another ancient cone-bearing tree that was thought to be extinct but was later discovered growing in a remote valley of Central China is the dawn redwood (Metasequoia glyptostroboides). The genus Metasequoia was first described from fossil material by the Japanese paleobotanist Shigeru Miki in 1941. In 1948, paleobotanist Dr. Ralph Chaney of the University of California, Berkeley led a 10,000 mile expedition up the Yangtze River and across three mountain ranges to a lush, fog-shrouded valley where a thousand dawn redwoods were growing. Leaf imprints and petrified wood of ancestral dawn redwoods resembling the present-day species have been found in Cretaceous deposits throughout North America. Some of the fossils date back nearly 90 million years, from a time when the climate was much more humid than today. It has been estimated that the relict forest in China may have been surviving in this remote primeval valley for countless thousands of years. The seed cones and foliage of the dawn redwood superficially resemble our California coast redwood (Sequoia sempervirens), except that the dawn redwood is deciduous and loses its leaves during the winter months. All North American plantings of this superb cone-bearing tree came from the seeds (and their progeny) originally collected in China. Indeed this "living fossil" was brought back to its ancestral home.

The ancient trees in most North American petrified forests are in horizontal positions. They were carried by streams and deposited in alluvial flood plains. Petrified trees on Specimen Ridge are unusual because they are still in their upright positions. Volcanic eruptions in this region during the Eocene epoch (50 million years ago) triggered massive landslides into mountain and valley streams. The mixture of ash, water and sand buried entire forests in their original standing positions, including redwood trees very similar to those of coastal California. Before the wood decayed, silca from the volcanic mud flow replaced the cell contents (lumens), literally creating forests of stone. Unlike other petrified woods that are completely replaced with minerals, the petrified trees of this region have lignified cell walls of the original xylem tissue that are still intact.