Abies_koreana

Fir Trees

Primarily denizens of mountainous terrain, firs (Abies spp.) are handsome, evergreen conifers. Most species grow in the temperate latitudes of North America, Europe, Asia and Africa, but two species are capable of withstanding especially cold temperatures – a fact that allows them to grow in the harsh boreal regions of North America and Europe.

Classification of Firs

Scientists debate the exact composition of the group, but most recognize approximately 50 different species. Although the group is quite speciose, the constituent species usually occur as “complexes” that share close genetic ties and appearances. In places with more than one species, identification can be challenging.

Despite the similarities of their common names, Douglas firs (Pseudotsugamenziesii) are not true firs at all.

Physical Description and Characteristics

Examination of the needles helps to distinguish fir trees from lookalikes. Fir needles are generally soft to the touch, flat in cross section and attach to the branch via suction-cup-like structures. If you pluck a needle from a branch, it will usually separate cleanly, without leaving a small peg behind as, for example, spruce trees (Picea spp.) do. The needles of firs often persist for a considerable length of time. Many species retain their leaves for five years or more, and some – notably Pacific silver firs (Abies amabilis) – may retain their leaves for decades.

While young, most fir trees exhibit a pyramidal growth habit and dark green foliage. Fir branches emerge from the central trunk in a whorled pattern. Because most firs produce a new set of whorls each year, you can often determine the approximate age of the trees by counting the whorls, although this may not be effective for specimens of advanced age. Further highlighting the specific growth habits of the species, each living branch usually grows in the same fashion each year: A longer terminal branch and two lateral branches are produced on each. Although the branches of some Nordmann firs (Abies nordmanniana) droop slightly, those of most firs do not.

Eye-Catching Cones

In addition to their handsome foliage and growth habit, firs have incredible looking cones, which stand upright on the branches. Many firs produce cones at a relatively early age, especially Korean firs (Abies koreana), which often produce cones by the time they reach 2 feet in height. Most fir cones start out blue or purple in color, although they darken with age.

The cones are resinous and occur on year-old branches. Maturation of the cones, which grow to almost 10 inches in some species, takes but a single season. Unfortunately, the cones of firs fall apart to release their seeds once they mature – a condition that botanists refer to as dehiscent.

Free Range Firs

Wild firs typically occur on good sites, with ample soil moisture and deep, fertile soils. Firs grow relatively quickly, but they are not especially long-lived trees. While occasional examples may survive nearly 500 years, most such specimens are capable of doing so because they spend many years suppressed by the dense shade produced by mature trees. Most firs are moderately sized trees, but a few – particularly the grand fir (Abies grandis) – exceed 200 feet in height. Most firs have relatively thin, flaky bark, which offers them little protection against fire.

 

Commercial Uses

Unlike many other conifers, whose woods possess insect- and decay-resistant qualities, fir wood degrades quickly once harvested. Accordingly, fir wood is rarely grown for timber production. It is primarily used to produce pulp, although some craftsmen use it for indoor applications. Unsurprisingly given their growth habit and aesthetic appeal, fir trees are frequently farmed for use as Christmas trees.

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Arborvitae

Arborvitaes are evergreen conifers, native to North America and Asia. Thanks to their hardy nature, they are quite popular among homeowners, arborists and landscape designers.

Additionally, arborvitaes, whose name translates to “tree of life” in Latin, provide a bounty of food for the local fauna. This means that these beautiful trees are not only popular among humans – animals love them too.

What’s In a Name?

Botanists and tree care professionals use the term arborvitae to describe any of five different tree species, which belong to the genus Thuja.

Three species are historically native to Asia:

  • Korean arborvitae (Thuja koraiensis)

  • Japanese arborvitae (Thuja standishii)

  • Sichuan arborvitae (Thuja sutchuenensis) – Extinct in the wild

Two species call North America home:

  • Eastern arborvitae (Thuja occidentalis)

  • Western arborvitae (Thuja plicata)

Some people refer to arborvitaes as cedars, which can lead to confusion, as arborvitaes are not members of the genus Cedrus – the true cedars. Others use the terms redcedar or whitecedar when referring to these trees. These names are not as problematic, but by using the term arborvitae (or Thuja), you can avoid most of the confusion entirely.

Historically, scientists placed several other trees in the genus Thuja, including Chinese swamp cypresses (Glyptostrobuspensilis), Athel pines (Tamarix aphylla) and Alaskan cypresses (Cupressus nootkatensis). However, plant taxonomists currently assign these species to other genera.

Physical Characteristics

During their first year of life, arborvitaes produce needle-like leaves; thereafter, their leaves take on a scale-like appearance. The leaves occur along branches arranged in flat splays radiating out from the trunk. Small seed-bearing cones sit along the ends of the boughs. Although they begin as small, tightly closed, greenish yellow structures, they turn brown and open to release their seeds upon reaching maturity. In the fall, older, interior branches may turn brown and die off. This is a natural part of the trees’ biology and no cause for concern.

Horticulturists have produced several arborvitae cultivars (and hybrids), such as Nigra and Smaragd. Whereas most wild-type arborvitaes exhibit a columnar growth habit, several cultivars become round, globe-like trees or shrubs. The leaves of some forms bear golden foliage, rather than the emerald green color typical on most other varieties. Most cultivars originate from the Eastern arborvitae.

Uses and Suitability

Part of the appeal of arborvitaes (at least some cultivars) is their rapid growth rate, which can exceed 2 feet per year when planted in good locations. This rapid growth rate appeals to homeowners and developers faced with bare lots and front yards. Many employ arborvitaes as specimen trees or ornamentals, but thanks to their dense foliage and upright, often columnar, growth habit, arborvitaes are among the most popular choices for privacy screens and hedges. Although most arborvitaes remain between 40 and 60 feet in height, some members of the genus (Thuja plicata) may climb over 200 feet high, so it is important to select a variety suitable for the site.

Despite the fact that the wood of arborvitaes is soft and lightweight, it is commonly used in a variety of applications. It’s resistance to decay makes it well suited for making fences, sign posts and other items that are exposed to the elements. Characteristically aromatic, the odor of the wood (which most people find pleasant) repels moths and other insects to some degree, which leads craftsmen to use it in the production of clothing chests and closets. Additionally, luthiers and others who construct stringed instruments often incorporate arborvitae wood into the instruments, such as guitars.

Ecology

Arborvitaes nourish a variety of animals, including those considered beneficial as well as pest species. Deer are especially fond of arborvitae foliage, as are porcupines, squirrels, rabbits, hares and beavers. Many songbirds eagerly consume the seeds and make their nests in the tree’s branches.

Although they are susceptible to a few pests and pathogens (particularly a few types of blight); arborvitaes are usually problem-free trees. Although bagworms may feed on over 100 different tree species, they often feed on arborvitaes. Hedge-like plantings are especially vulnerable to these pests, while those planted as specimens or ornamentals are less susceptible to serious infestation. Typically, hand removal of the bagworms is the preferred method of control, as the bugs’ protective encasement offers them some protection from insecticides.

true redwoods

True Redwoods

Coastal redwoods (Sequoia sempervirens) are among the most famous trees in the world. Most of this fame precipitates from their incredible size, as they are among the tallest species on Earth.

However, coastal redwoods are more than just really tall trees – they also provide a number of examples of evolutionary adaptation, from their reliance on fog for moisture and their ability to maintain lush canopies, despite the harsh conditions found at these elevations.

Basic Description

Coastal redwoods are evergreen conifers with small, rounded canopies. Their branches usually droop slightly at the ends, and the tree’s red bark usually fades to gray over time.

Coastal redwoods bear different leaves on different portions of the tree. Flat, long leaves are found on young branches and shaded canopy branches, while scale-like leaves are found on the sun-drenched leaves of the canopy. Intermediate leaves adorn branches in transitional areas.

The scale-like leaves found at the tops of the trees help to slow evaporation. This is a crucial adaptation, as the high temperatures and low humidity found at these heights would quickly cause the trees to dehydrate, if they did not place some limits on the rate of evaporation.

Record Holders

Coastal redwoods are unquestionably the tallest trees in the world. The record holder, named “Hyperion”, measures almost 380 feet in height; unfortunately, woodpecker damage near the top of the tree will probably limit any future growth. However, many other redwoods are nearly as tall — more than 10 trees reach heights in excess of 367 feet.

Water Acquisition

Even though established redwood trees are somewhat resistant to drought stress, large trees require large quantities of water to remain healthy. Accordingly, redwoods have been forced to develop supplemental methods for collecting enough water.

In addition to drawing water up their roots, as most other trees do, redwoods utilize fog as a water source. As the fog condenses on their leaves and branches, it rolls off onto the ground below. This fog is so crucial to redwoods that their natural range stops about 50 miles from the Pacific Coast, which marks the maximum penetration of fog in the region.

However, much of this condensed water evaporates before it soaks into the ground. Therefore, while the ground has more moisture than it would have without the fog water, the precious resource is still at a premium. To help the trees further meet their moisture requirements, they rely on a dense mat of mycorrhizal roots to draw water more efficiently from the ground. The mycorrhizae increase the surface area of the roots drastically, which enables the immense trees to draw more water than they would otherwise be able.

Limits to Height

Though they reach heights that other species fail to attain, coastal redwoods face a barrier that prevents them from becoming taller: The method by which they hydrate themselves. Just like other trees, redwoods draw water from the ground and allow it to evaporate from their leaves; however, there are limits to how far water can be drawn in this manner. It appears that, were coastal redwoods to grow much taller, they would be unable to maintain a continuous column of water in their xylem cells, which would lead to air bubbles forming in the wood.

These air bubbles would stop the flow of water up the tree, and in many cases, prevent that section of the tree from carrying water in the future. Accordingly, redwoods approach the limits for tree height on our planet – no trees are thought to be able to grow much taller.

Trees try to prevent this problem by reducing the amount of evaporation escaping from leaves in the canopy. While this reduces the risks of air bubbles forming in the wood, it reduces the growth rate of the trees. Once again, fog plays a critical role in the lives of these trees, as it reduces the amount of water that evaporates from the leaves. This allows the tree to continue to draw water from the ground, and ultimately grow much higher than other trees.

Albinos

Some redwoods produce pale, white or off-white foliage. These specimens are “albinos”, who fail to produce chlorophyll. In some cases, entire trees are albinos, but, more commonly, albinos occur as portions of otherwise normal trees. Called chimeras, such trees possess two different genomes.

In both cases, these pale white leaves cannot produce food for the tree. In the case of chimeras, the tree’s other, healthy leaves produce enough food to make up for the handicapped leaves. In the case of trees that lack chlorophyll entirely, they survive by forming root grafts with nearby, healthy specimens. From within these grafts, the albino trees can draw enough energy to survive.

While it is possible that albino trees survive in spite of their condition, some researchers believe that albinism may be a response to stress. Given the lack of suitable rainfall over the last few years and the fact that most albinos occur on marginal sites, the idea is not without merit.

Sequoiadendrons

Sequoiadendrons

Giant sequoias (Sequoiadendron giganteum) are famous for being some of the largest organisms on the planet. Known colloquially as big trees, Sierra redwoods, Sequoiadendrons, or simply sequoias, these trees have been one of the most important species in Northern California for millions of years.

Although they are among the most robust and resilient macro-organisms the world has ever seen, their population is in decline, and their long-term future is uncertain.

Giant with a Capital “G”

Although they do not climb as high as their relatives the coastal redwoods (Sequoia sempervirens) do, giant sequoias are the world’s largest trees with respect to volume. The largest specimen currently known — a 275-foot-tall tree living in Sequoia National Park that bears the name “General Sherman” — occupies over 50,000 cubic feet of space and weighs about 2.7 million pounds. By contrast, the volume of the tallest coastal redwood – “Hyperion”, a coastal redwood — is only about 18,000 cubic feet.

To provide some context, if General Sherman were planted next to the Statue of Liberty, the top of the canopy would be about 15 lower than the top of the torch.

Ancient Trees

Many of the giant sequoias living in the Sierra Nevadas are among the oldest organisms on the planet. While the oldest documented specimen was only about 3,200 years old, it is likely that these trees can reach ages of 4,000 to 5,000 years. Some botanists have even speculated that a few specimens may reach twice these ages.

However, unlike some other trees that live very long lives, giant sequoias mature relatively quickly. Most specimens begin producing cones by 20 years of age. This allows the trees to produce a ridiculous number of seeds over their lifetimes. Because each tree holds approximately 11,000 cones, and each cone contains about 230 seeds, giant sequoias often hold about 2.5 million seeds at any point in time.

However, the cones must dry out to open and release the seeds, so many cones lay dormant for several years. This high fecundity is necessary because the seeds require extremely specific conditions in order to germinate. Therefore, only a small percentage of the released seeds become new trees.

Fire Resistance

The only way that trees can reach great ages in the western United States is by developing methods to survive periodic fires. To that end, giant sequoias have evolved one of the thickest barks known in the world, which may be 2 feet thick in places. Additionally, the bark has very little resin, which makes it further resistant to fire.

When fires move through sequoia-dominated forests, the giants usually survive, while thin-barked trees (including sub-mature sequoias) perish. This provides new ecological space in which young sequoias can grow, so the seed-bearing cones usually open in response to fire. Forest-grown specimens tend to shed their lower branches, thereby offering further protection against fires, as it reduces the chances that fire can climb into the delicate canopy.

 

Mortality

Part of the reproductive strategy for giant sequoias relies on mature trees living very long lives. This gives them the time to produce an unthinkable number of seeds over their lifetimes. Accordingly, the trees have evolved a number of adaptations that allow them to survive for thousands of years.

Part of their success precipitates from the fact that mature giant sequoias only face a few threats. Chainsaw-wielding humans have killed more sequoias than any other cause over the last 100 years, but they need not fear many other animals, including insects or other pests. The mighty trees have few problems with disease and are they relatively immune to fire. As gigantic trees, they often serve as lightning rods, but even those that are struck often manage to survive.

The primary non-human causes of their mortality appear to be wind, fire and erosive forces. For example, over hundreds of years, a river or run-off channel may undercut the foundation of the tree, causing it to topple.

Extinct Trees

Giant sequoias are not the only member of the genus Sequoiadendron – an extinct species, called Sequoiadendron chaneyi, is known from the fossil record. This extinct species inhabited the Colorado Plateau until sometime between 5 and 15 million years ago. Many paleobotanists believe that S. chaneyi was the direct ancestor from which S. giganteum evolved.

Taiwania cryptomerioides

Taiwania Trees

Taiwania trees (Taiwania cryptomerioides) are large evergreens, native to East Asia. Relatively poorly known among North American tree enthusiasts, these immense trees can make interesting specimen trees in yards and commercial areas, provided that you can find specimens for sale.

Description

Taiwania trees grow in two different patterns throughout their lives. As young trees, they produce long, pendulous branches along most of the trunk, giving the entire tree a pyramidal shape. However, as they reach about 40 to 50 feet in height, they begin taking on their mature form. At this point, they begin shedding their lower limbs, which results in a bare bole for two-thirds of the tree’s height. The canopy is thereby restricted to the upper third of the tree, and often takes on an irregular, shaggy appearance.

As with the growth-form dichotomy, Taiwania trees produce leaves of two different shapes. The leaves on young specimens are awl-like, and reach about one inch in length; leaves of mature trees are scale-like and lay flat against the branches. No matter the age of the tree, the leaves are usually a very attractive shade of blue-green, although some individual trees produce a more subdued green foliage.

Small cones adorn the tips of the branches, but only on mature specimens that already produce mature foliar patterns. The bark is reddish brown, although older specimens may turn gray from weathering. The bark flakes away in strips, and becomes fissured over time.

Emergent Species

Taiwania trees reach immense sizes and are among the largest Asian species. The tallest specimens exceed 200 feet in height, rivaling or surpassing many North American giants, such as tuliptrees (Liriodendron tulipifera), white pines (Pinus strobus), noble firs (Abies procera) and Douglas firs (Pseudotsuga menziesii). The tree often grows as a minor component of forests, represented by emergent individuals, who tower above the canopy. However, they also form pure stands in a few locations.

Human Usage

Named after the location in which they were first discovered, these trees have long been prized for their soft, yet durable lumber. Additionally, the wood often bears attractive yellow and red rings, which make it popular among craftsmen. They were historically used in temple construction and for coffins (which led to their other common name – coffin trees), but thanks to years of overharvesting, the trees are no longer as plentiful as they once were in the wild.

This has led the IUCN Redlist to classify them as “Vulnerable” in most of their range and “Critically Endangered” in Vietnam. Several Asian governments have responded by bestowing legal protections on the species. However, the trees grow quickly in a cultivated setting, and many plantations in the region produce these large trees.

Cultivation

Taiwania trees eventually attain massive size, but according to the 2010 Yearbook published by the International Dendrology Society, no North American specimens have reached maturity. In most cases, cultivated Taiwania will fail to reach their natural potential, thus keeping them small enough for some spaces. Additionally, Taiwania trees possess a number of traits that make them otherwise suitable as shade or specimen trees. However, they are somewhat difficult to acquire in the commercial market, so they are rather rare in privately owned properties.

Although they require strong, direct sunlight to grow well, Taiwania trees tolerate light shade. They are not drought tolerant by California standards, although established specimens withstand droughts in the southern United States. Low temperatures are rarely a problem, especially if other trees or buildings shield them from the wind. They can likely tolerate U.S. Hardiness Zones 7 through 10. Timber companies often grow them in the Southeastern United States, as do many horticultural parks throughout the western half of the country.

Bald Cypress

Bald Cypress

Found in swamps, floodplains and riparian areas throughout the Deep South, bald cypresses (Taxodium distichum) are some of the most iconic trees in the country.

Often draped with moss and growing straight out of the water to heights in excess of 100 feet, bald cypresses are unmistakable. Bald cypresses play important roles in the habitats in which they grow, and they are an important species that has been used by humans since the dawn of the 20th Century.

Description

Like pines (Pinus spp.), hemlocks (Tsuga spp.) and other cone-bearing trees, bald cypresses are conifers. They bear flat leaflets, arranged in two rows along the branchlets. Unlike most other conifers, bald cypresses are deciduous, meaning that they shed their leaves in the early winter. Before they fall from the trees, the needle-like leaves turn rich red, orange or brown.

Bald cypresses are large trees, and the tallest individuals stand over 140 feet high. However, it takes them quite a while to reach such heights. Fortunately, these long-lived trees are capable of living to very advanced ages – a few living individuals are known to be more than 1,500 years old.

Swamp-dwelling bald cypresses are famous for producing woody structures called “knees”. Knees emerge from the roots, often extending above the water line. Their exact function is not clear, but some hypothesize that they serve as a place for oxygen absorption. When grown in areas without standing water, bald cypresses fail to produce knees.

Habitat and Ecology

Cypress trees form the backbone of most habitats in which they grow, thanks in large part to their ability to grow in flooded habitats. This allows them to form huge forests in areas that would otherwise harbor few trees. These trees not only provide the plants and animals living under their canopies with shelter and protection from the elements, they also produce microclimates that enable countless plant and animal species to live among them.

One of the species that depends heavily on cypresses is Spanish moss (Tillandsia usneoides). Although its common name suggests that it is a moss, it is actually a type of rootless flowering plant called an epiphyte. Although Spanish moss can grow on a variety of tree species, it appears to favor bald cypresses, pond cypresses and live oaks (Quercus virginiana).

The Spanish moss growing on these trees actually forms a microhabitat of its own. The plant’s leaves serve as roosting sites for a number of bats and birds, as well as hunting grounds for insectivorous lizards and frogs. In fact, the moss serves as the only known habitat for Pelegrina tillandsia – a tiny jumping spider.

Waterfowl and rodents, particularly squirrels, eat and spread cypress seeds, but the trees also spread their seeds via water. They float downstream, often ending up on a sandbar or shoreline. Once there, the seeds germinate they grow quickly, in order to avoid drowning in upcoming floods. In ideal places, the young trees may grow more than 2 feet in their first year.

Relatives

Although they are perhaps the most well-known members of the group, bald cypresses are but one representative of the genus Taxodium. The pond cypress (Taxodium ascendens) inhabits nearly the same range as the bald cypress, yet it is associated with slightly different habitats. Being very similar in morphology to bald cypresses, pond cypresses are treated as a variety of the bald cypress by some authorities.

Pond cypresses may produce knees, as their more familiar relatives do, but they do not produce as many, nor do they reach the size of those produced by bald cypresses. Pond cypresses often bear ascending branch tips (hence their specific name), and they bear awl-shaped leaves, which are held flat against the twig.

The third and final member of the genus is the Montezuma cypress (Taxodium mucronatum). Found in extreme southern Texas and throughout much of Mexico, the Montezuma cypress often produces very large trunks. In fact, the living tree with the greatest documented diameter is a member of this species. The record-holder – called Arbor del Tule by locals — has a diameter of over 37 feet. Unlike its relatives, the Montezuma cypress rarely produces knees and often acclimates well to highland locations.

Like the pond cypress, the Montezuma cypress is considered a variety of the bald cypress by some authorities.

Cultivation

Despite the fact that they are highly specialized trees of southern swamps, bald cypresses often thrive in a variety of locations. They are rated for hardiness zones 4 through 10, and – despite their ability to grow in standing water – often adapt well to arid locations (they do require abundant water during their establishment period). Obviously, bald cypresses are supremely well adapted to areas that experience occasional flooding.

Bald cypresses grow to respectable sizes over human time scales; large specimens reach 75 feet in height, with full, 30-foot-wide canopies. The combination of their beautiful fall foliage and picturesque winter form help to make bald cypresses visually interesting components of backyards, parks and commercial areas.

True Cypresses

Although many different tree species include the word “cypress” in their common name, the true cypresses are a closely related subgroup of these trees.

Historically, the term “true” cypresses referred to conifers of the genus Cupressus. However, the classification scheme for these trees and their close relatives has been revised several times, and different authorities often present conflicting taxonomic arrangements.

Taxonomy and Species

Using the most inclusive definition, the genus contains about 26 species. These form several sub-groups, which some scientists recognize as either genera or subgenera. Most of the modern work conducted to illuminate the relationships among the various members of the group has relied on DNA analysis.

  • One group is comprised of all but one Old World Species. Some researchers call this group the genus or subgenus Cupressus.

  • Another group is comprised of all but one New World species. This group often goes by the genus or subgenus Hesperocyparis.

  • The Vietnam cypress (C. vietnamensis) is sometimes placed in its own genus or subgenus, named Xanthocyparis.

  • The Alaskan yellow cedar (C. nootkatensis) is sometimes assigned to the genus or subgenus Callitropsis.

Many members of the genus occur in small, isolated geographic areas. The differences between these populations are often subtle, leading different workers to reach different classification-oriented conclusions.

Description and Variation

Regardless of the taxonomic scheme in use, true cypresses bear several obvious physical similarities, although they may grow as either shrubs or trees. A few species are capable of attaining very large sizes — the Alaskan yellow cedar may approach 200 feet in height.

While the various forms often share a similar appearance and form, others grow uniquely. For example, the Monterey cypress (Cupressus macrocarpa) often develops a flat-topped canopy, courtesy of the strong winds that dominate in their cliff-side habitats. Conversely, the Arizona cypress (Cupressus arizonica) a close relative found a few hundred miles inland, produces a conical canopy, as it is not subject to intense, constant winds. Additionally, being better adapted to the hot summers of its homeland, the Arizona cypress is not as susceptible to cypress canker, which often afflicts Monterey cypresses forced to cope with hot summers.

The Mexican cypress (Cupressus lusitanica) is a popular ornamental species, which tolerates hot temperatures and droughts. The Gowen cypress (Cupressus goveniana) and the Mendocino cypress (Cupressus pigmaea) are two California natives, but various authorities classify these enigmatic forms differently. Both forms are closely related, variable and often grow in the same locations.

The Alaskan yellow cedar is found along the Pacific Coast as far south as northern California. The pendulous branches of these graceful cypresses make them popular ornamental specimens. Many of the trees growing at northern latitudes require a thick layer of snow to shield the roots from the bitter cold of Alaska’s winters. Because the amount of snow has decreased in recent years, these trees have begun suffering from frost damage.

Ecology

The true cypresses are native to several different regions of the world. They live from the temperate forests of Canada and the United States, down along the western portion of the continent into Mexico and Central America. They are also found in the Middle East and Northern Africa, and throughout the Himalayan region to China and as far south as Vietnam.

The tree’s globular seed cones develop over a period of 1 to 2 years, and many only open and release their seeds after the parent tree has been killed in a fire. The evergreen leaves are scale-like, and are superficially reminiscent of arborvitae leaves. Like some other conifers, the young leaves may be awl-shaped and pointed.

Cultivation

The widely planted Leland cypress (Cupressus × leylandii) is a hybrid tree created by the crossing of the Monterey cypress and the Nootka cypress (Cupressus nootkatensis). While the weak-wooded tree has largely fallen out of favor among arborists, the tree is still valuable in some cases, as it grown remarkably fast and is tolerant of a wide variety of soil types.

Dwarf Redwoods

The dwarf or dawn redwood (Metasequoia glyptostroboides) is one of three species that bears the redwood moniker.

The sole living species of its genus, dwarf redwoods are very attractive conifers, who are quite similar to coastal redwoods (Sequoia sempervirens). Some botanists even contend that the dwarf redwood is the direct ancestor of the coastal redwood.

Although smaller than the other two types of redwood, the term “dwarf” is somewhat misleading, as these trees may reach 200 feet in height.

Description

Unlike their taller cousins, who keep their leaves all year long, dwarf redwoods are deciduous trees, which shed their leaves in the winter. The leaves of dwarf redwoods are bright green in the spring and summer, but they turn yellow, red or orange in the autumn; in the winter, the trees appear as majestic skeletons, devoid of leaves.

The shape of their leaves and tendency to form wide, buttressed trunks (the trunks of some specimens exceed 15 feet in diameter), causes some to mistake these trees for bald cypresses (Taxodium distichum). Both species are most common in riparian or flood plain habitats. However, you can distinguish between the two by noting the leaf arrangement: Dwarf redwood leaves are arranged oppositely, while those of bald cypresses are arranged in alternate fashion.

Discovery and History

In 1941, paleobotanists identified dwarf redwoods fossils, but they were thought to be extinct. However, a few years later, conservationists working in southwestern China found several living specimens. Interestingly, the fossilized trees were almost identical to the modern species, meaning that these trees have changed very little over the last 65 million years. This has led many to call the tree a “living fossil.”

Scientists believe that these trees were once quite widespread throughout the Northern Hemisphere. Although the exact cause of their decline is unknown, habitat alteration – such as the conversion of large tracts of land from forest to agricultural fields – was likely an important factor. Many of the remaining trees likely grew alongside ancient floodplains.

Status and Conservation

Because these trees only grow in a small geographic area, they are considered an endangered species. While conservation programs are in place, the excessive pollution associated with the use of coal is threatening many naturally growing populations. Trees that grow in places where the local citizens rely on coal for heat often shed their leaves earlier and produce less fruit than those trees that grow in undisturbed areas. Another challenge facing conservationists is the relatively low genetic diversity found within living specimens. A product of their long history of isolation, this low genetic diversity may lead to the proliferation of undesirable traits.

Uses and Cultivation

Designated as “Endangered” by the IUCN Redlist of Threatened Species, all wild-growing dwarf redwoods are protected in China. Accordingly, they are not used as a commercial timber species. Nevertheless, the trees have been cultivated and planted in several locations around the globe. They grow readily from cuttings, which has helped increase their appeal and hasten their spread throughout the world’s gardens and parks. The trees exhibit remarkably different growth habits when used as an ornamental, which probably relate to differences in growing conditions, rather than genetic diversity.

Dwarf redwoods are incredibly fast-growing trees. When planted on a good site, the young trees may exceed 130 feet in height, by the time they are 100 years of age.

Juniper Trees

The genus Juniperus contains between 50 and 68 different species, depending on the authority consulted.

Juniper trees inhabit much of the world’s land area, including parts of North America, Europe, Asia and Africa. Junipers are common plants and trees across arid regions of the American southwest; in many places, they are the primary tree species present.

Most individual species have fairly restricted ranges, but one species – the common juniper (Juniperus communis) – is the world’s most widely ranging conifer. It is the only member of the genus to live in both Europe and North America.

Description and Form

Junipers have awl- or scale-like leaves; some species possess only one type of leaf, while others bear both types. For example, common junipers possess only the awl-like leaves, while Chinese junipers (Juniperus chinensis) produce both awl-like and scale-like leaves. The leaves are typically dark green in color.

Like many other members of the family Cuppressaceae, some junipers live very long lives. Some Rocky Mountain junipers (Juniperus scopulorum) are known to have lived for over 2,000 years. The trees produce very narrow growth rings, which makes them a coveted timber species.

California’s own juniper species – the California juniper (Juniperus californica) – lives primarily within the state’s borders. Usually growing as a shrub, the plant also grows as a short tree, reaching about 25 feet in height.

Odd, But Useful Cones

Junipers have odd cones, whose scales grow together around the seeds. They look like, and are often mistaken for, berries. Inside the blue (rarely orange) flesh, the cones hold up to a dozen tiny seeds. They rely heavily on the seed dispersal activities of birds, which leads them to grow in places under which birds congregate, such as fencerows and under utility lines.

Humans use the cones in a variety of culinary applications. Perhaps best known as the primary flavoring agent in gin, juniper berries are also used in spices, sauces and to flavor some beers. The very word “gin” is a corruption of the word “genever” – the Dutch word for juniper. Primitive cultures have used the berries for a variety of medicinal purposes (to varying degrees of efficacy), such as inducing labor or miscarriage, treating diabetes and relieving the symptoms of asthma.

Use and Cultivation

Juniper wood is extremely resistant to decay and insects, which make is very useful for outdoor construction. Humans use junipers extensively for ornamental plantings, and because they often tolerate arid conditions and are unpalatable to many foraging animals, they are helpful for soil stabilization projects.  Numerous cultivars have been produced, some of which grow as sprawling ground covers while others form upright, single-trunked trees.

Junipers typically adapt well to a variety of different well-drained soils, but most require full sun exposure or light shade to grow. However, they form coarse root systems, which make them very difficult to transplant, except while they remain young. Many junipers — especially the improperly named red cedar (Juniperus virginiana) — produce very dense foliage, which makes them useful for windscreens or providing privacy. Although they are not common street trees, their hardy nature, ability to adapt to varying soil conditions, strong wood and lack of maintenance problems make them excellent candidates in some areas.

Despite their many positive traits, some Junipers are susceptible to a variety of pest and pathogens. For example, bark beetles, aphids and mites frequently feast on the trees, cedar-apple rust and various heartwood rots represent threats to the trees. Additionally, some forms produce prickly foliage, which some people may find undesirable.

Oriental Swamp Cypresses

Also called the water pine, the Oriental swamp cypress (Gylptostrobus pensilis) is the sole member of its genus. Native to China and neighboring portions of Vietnam, the trees show many similarities to their close relatives, the bald cypresses (Taxodium spp.).

Like bald cypresses, Oriental swamp cypresses commonly grow in low-lying, damp areas. They often grow best in flooded sites, including areas with up to 24 inches of water.

To cope with constantly flooded conditions, Oriental swamp cypresses often produce pneumatophores — roots that grow upward to access oxygen (often called “knees”) — just as their relatives do.  However, the Oriental swamp cypress does not grow as quickly as its relatives do. These deciduous trees usually leaf out later in the year than their relatives do, and they shed their leaves later in the autumn.

Description

Oriental swamp cypresses are medium- to large-sized trees, which may reach 100 feet in height, although most specimens are less than 80 feet tall. However, specimens planted outside their native range usually remain less than 40 feet tall.

Oriental swamp cypresses are often the dominant species in the swampy habitats it calls home, and occasionally it forms pure stands. These trees are monoecious – individual plants bear both male and female flowers – and are pollinated via the wind. The trees deciduous leaves are arranged spirally around the branches, but they are twisted at the base, which makes them lie in twin horizontal splays. The inch-long cones open at maturity to release the seeds.

Cultivation and Use

Oriental swamp cypresses are planted widely for a variety of purposes. They are planted as ornamentals in Europe and North America, while some Chinese farmers plant these trees near rice paddies and agricultural areas to help stabilize the soil and reduce the rate of erosion.

Oriental cypress trees require full sun exposure, although they adapt readily to most soil types. However, as they are not drought tolerant, and are likely to die within 24 months when planted in dry soil, oriental swamp cypresses are not an ideal selection for most Californians.

Commercial Application and Harvest

The timber from Oriental swamp cypresses is highly valued for fence posts and similar applications, due to its insect and rot resistance. The fine-textured, aromatic wood is also suitable for finer work, and is used to construct musical instruments and furniture. The roots of these trees are exceptionally buoyant, so they are used in the construction of buoys and similar goods. Tannins from the bark are harvested for use as dyes.

Many locals believe Oriental swamp cypresses are lucky, so only those that have fallen over naturally are now milled into useable timber.

Status in the Wild

Unfortunately, the value of the timber has taken a toll on wild populations of the tree, and it has become extraordinarily rare in the wild – the IUCN Redlist recently upgraded the species to critically endangered, upon finding no wild specimens in China and only a few in Vietnam. (IUCN, 2011) Botanists estimate that over 250 individual, wild-growing trees exist, but very few of these – if any – continue to produce viable seeds. In addition to overharvest and illegal logging activities, habitat alteration – such as the draining of swamps – has also reduced natural populations.