The Tree

by Colin Tudge

  The genus Araucaria, for which the whole family is named, has nineteen species, of which no fewer than thirteen are endemic to New Caledonia—meaning they occur nowhere else. New Guinea has several Araucaria, too, and so does Australia. Well known in Europe and America—though not too far north (except as an unusual houseplant) because it’s tender—is the beautiful Norfolk Island “pine,” Araucaria heterophylla, which grows straight as a Christmas tree but with branches that curl up at the ends; it’s much favored in the prestigious gardens of embassies and smart hotels in warm countries the world over. But the araucarias best known to northerners are the only two species that are native to South America. The monkey puzzle tree (a.k.a. Chile pine), Araucaria araucana, from Chile and Argentina, was once a favorite in suburban gardens (and is still hanging on there; many are only just coming into their pomp). The leaves of the monkey puzzle are leathery and spiky and cling closely to the stems. Perhaps they do give monkeys pause for thought—but monkeys did not appear in South America until about 30 million years ago, and the genus Araucaria, apparently far older than Agathis, was around about 120 million years before America had any monkeys at all. Perhaps the monkey puzzle had no thought of monkeys but evolved its daunting leaves to deter dinosaurs. (So, at least, some botanists have speculated. Certainly, trees are incomprehensible until and unless we consider their past.)

  The monkey puzzle has poor timber, but the Parana pine (Araucaria angustifolia) is much loved by do-it-yourselfers for its lovely variable colors, from smooth creamy white to chestnut brown and rich streaky red, tough but not too tough to work with tools of ordinary steel. The Parana pine grows mainly in Parana, Brazil, and also in Paraguay and Argentina, as a flat-topped tree up to 40 meters high with a straight clear bole around 1.2 meters in diameter. It is sometimes known as Brazilian pine and is Brazil’s chief timber export.

  Wollemia, the third remaining genus of this once great family, is the archetypal relict—to be ranked with the coelacanth, the ancient lobe-finned fish that was found in the ocean depths near Madagascar in the 1930s. For until 1994 Wollemia was known only from fossils, dating from 120 million years ago. Then a group of thirty or so turned up at the bottom of a canyon in the Blue Mountains of New South Wales, Australia. They were growing alongside flowering trees by a stream. They don’t seem to be holding their own in the wild and must now be actively conserved. Finding Wollemia was not quite like finding Tyrannosaurus rex, but it is conceptually similar.

  Nowadays there are no Araucariaceae in Africa, although the fossils show they were there in the past; or, of course, in Antarctica, where they once abounded; or in the Northern Hemisphere as a whole, though they were once widespread there. Truly they are a relict group, and we should be grateful for the survivors.

  THE PLUM YEW AND OTHER EAST ASIANS:

  FAMILY CEPHALOTAXACEAE

  Here is another archetypal relict family with only one genus—Cephalotaxus—and just eleven species. It grows as an understory tree—a shade lover—in temperate forests on mountains, mixed with flowering trees, from the eastern Himalayas through China, Japan, Taiwan, Thailand, Vietnam, and Malaysia. Cephalotaxus trees are vaguely yew-like to look at (and in less sophisticated days were sometimes classed with the yews). They are known to Western gardeners by a variety of names, including “cow’s-tail pine,” because everything with dark green needle leaves tends to be called a “pine” sooner or later, and “plum yew,” because the female cones of Cephalotaxus give way to a single, soft-skinned seed that looks roughly like an olive—or an unripe yew “berry.”

  CYPRESSES, JUNIPERS, SWAMP CYPRESSES, AND REDWOODS: FAMILY CUPRESSACEAE

  The Cupressaceae is the only conifer family that occurs all over the world, on all continents (except Antarctica) and both hemispheres—it is impossible even to guess whether the family arose in the north (Laurasia) or the south (Gondwana). Cupressaceae also has the most genera of all living families of conifers—thirty—although not the most species (just 133). Yet its relict status shines through, for eighteen of those genera contain only one species. In each of them, the once possibly startling diversity hangs by a thread.

  The family Cupressaceae has been extended in recent years. In its earlier form, it included only the cypresses, the junipers, the Australian Callitris, and the thujas, which look like cypresses. But botanists had suspected for many a decade that there was no clear distinction between the Cupressaceae and the trees that were then placed in the Taxodiaceae—the swamp cypresses and the redwoods. Their cones are similar in significant details (not least in the way they develop), and the bark of a big cypress—thick, soft, and stringy—is indistinguishable from that of a redwood.

  Now it is clear that the old-style Taxodiaceae is not a coherent grouping. Really it’s just a group of genera that look roughly similar because they share primitive features—not because they have any special, close relationship. In fact, the various members of the Taxodiaceae are no more closely related to one another than some of them are to the old-style, narrowly defined Cupressaceae. The newly discovered Metasequoia seems particularly close to the cypresses. Thus the traditional Taxodiaceae family may be compared to reptiles or the bryophytes—not a true group (a clade) but a “grade”: a collection of creatures with similar general features. So the old-style Taxodiaceae are now combined with the old-style Cupressaceae to form a new, expanded Cupressaceae family. However, you will still find the traditional name Taxodiaceae on labels in botanic gardens. These things take time to catch up.

  The trees of the newly expanded Cupressaceae family live in an extraordinary variety of places. Some, like Chamaecyparis, Fitzroya, Sequoia, and Thuja, prefer very wet and tall forests on coasts. Others (Chamaecyparis, Cupressus cashmeriana, Taiwania) live in monsoon cloud forests high in mountains. Some (Callitris, Juniperus) thrive at the edge of deserts. One (Cupressus dupreziana) survives right in the heart of the Sahara, where there is virtually no rainfall, drawing its water from a fossil aquifer far beneath the surface. Some junipers live at the edge of the Greenland ice cap, in permanent snow. The various trees in their various habitats are correspondingly various in form: from the very squat, like Microbiota decussata, which hugs the ground for survival in the Russian far east, to the giant redwood (Sequoia sempervirens), which basks in the mists of coastal California and is the tallest tree of all. The Cupressaceae family also includes some of the world’s oldest living organisms—in the genera Fitzroya and Juniperus. Like the pines, the species of the cypress-redwood family are generally happy in poor soil—and some grow from crevices in rocks, apparently without soil at all.

  The old-style Cupressaceae family included twenty-two genera. Most of them contain only very few species, and some only one. Callitris is one of only three genera in the family that contain more than ten species. In fact, it has fifteen, of which thirteen live in Australia (two in Tasmania) and two (inevitably it seems) in New Caledonia. In general, Callitris favors upland semiaridity, and grows alongside eucalyptus as “fire climax” species: the kind that thrive when everything else is burned out. Callitris preissii (a.k.a. C. robusta) finds favor as a garden tree sometimes known as cypress pine.

  The sixteen species of Cupressus are the “true cypresses.” They span the Northern Hemisphere, happy on temperate, moist coasts, in deserts, or on high mountains. In southwest North America one species extends down into Honduras. Cupressus dupreziana, as we have seen, hacks it out in the Sahara. The “classic” cypress of the Mediterranean and the Middle East is Cupressus sempervirens (“always living”). Some Cupressus species are native to the Himalayas and western China. But in the Mediterranean and Asia in particular it is hard to decide which are truly native, because so many have been moved and replanted since Roman times, or perhaps even earlier. Calocedrus decurrens, from western North America, has the nostalgic whiff of school classrooms (at least as they were in my day), for its soft, fine-textured timber furnishes 75 percent of the world’s pencils.

  The genus Cupressus should probably be
extended to include the six species of Chamaecyparis; either that, or the two should first be combined and then split up again in new ways. The features that are commonly used to tell the two genera apart—notably, the arrangement of the leaves—do not seem to carry enough weight, when taken with other characters. Species of Chamaecyparis grow in North America and eastern Asia as tall trees in temperate mixed or all-coniferous forests, from sea level to the mountains. Best known is the garden favorite Chamaecyparis lawsoniana, Lawson’s cypress (a.k.a. “Port Orford cedar”) of southwest Oregon and northwest California. In Britain it is often grown as a hedge. In America (though not in Britain) it is acknowledged as a fine timber tree for furniture, ships, oars, paddles for canoes, and church organs. Leyland cypress (x Cupressocyparis leylandii), which grows so fast and casts the shadows that cause so much suburban strife, is a hybrid of Chamaecyparis nootkatensis (a.k.a. “Alaska cedar,” originally from the coast of northern California and Alaska) and Cupressus macrocarpus. Apparently the hybrid first arose in a garden in Montgomeryshire, on the English-Welsh border, at the end of the nineteenth century. The fact that these two hybridized so readily is another reason for thinking that Chamaecyparis and Cupressus should not be treated as separate genera. But as a further complication, Aljos Farjon and others have proposed that Chamaecyparis nootkatensis, together with a newly discovered conifer from Vietnam, should be placed in a new genus, Xanthocyparis.

  Fitzroya now contains only one species—the cypress-like F. cupressoides— but it’s a great one. It is native to the coast and up into the foothills of the Andes of southern Chile and Argentina (a wonderful place to see trees), and given time, it becomes massive. But it needs a great deal of time: the oldest living Fitzroya specimens that can be aged are at least 3,600 years old. Many of the oldest trees have been seriously mutilated by time. Lightning has split their protective bark, insects have chewed the wood within, fungus has rotted it away, and birds have probed for insects and made holes for nests, and now there is nothing left of the tree’s interior. The bark and the sheath of living tissue that lies within the bark are left standing like a monk’s habit, but with no one inside. When a tree has been hollowed out like this we may conclude that it is very, very ancient, but there is no way to judge its age precisely. The evidence is contained in the wood, and the wood is all gone. Sometimes Fitzroya grows with its own kind, in groves, and sometimes intermingled with the southern beech, Nothofagus.

  Juniperus is the biggest genus of the Cupressaceae: its fifty-three species account for nearly 40 percent of the whole family. Apparently (like some groups of pines), the junipers have radiated to form many new species in (geologically) recent times. Some live to several thousand years. Between them they span the Northern Hemisphere—and J. procera is found south of the equator in eastern and southern tropical Africa. They seem to tolerate almost anything, from subarctic tundra to semidesert, taking all forms, from ground-hugging shrubs to tall trees. Virtually all are drought-resistant. On mountains, some junipers grow to the topmost limit of the treeline. J. brevifolia is endemic to the Azores—and is the only conifer established on any midoceanic volcanic island. Its juicy “berries” must have been taken there by birds. J. communis is the most widespread conifer species of all, and has even put in an appearance as one of Britain’s three (possible) native conifers. Juniperus as defined here includes Sabina, a name that still features in many texts and may turn up on botanic labels but does not seem to be distinct enough to warrant generic status.

  Members of the genus Thuja are long-lived and cypress-like. The grandest of all the five species is Thuja plicata, known confusingly as the western red cedar—the “cedar” of the timber trade: fabulous all-weather wood that makes fine garden furniture and shingle roofs that will last a lifetime without further preservation. For good measure, too, its timber (as in most species of Thuja) is aromatic, and its leaves when crushed smell of pineapple. In its native Oregon, Washington, and British Columbia, western red cedar grows to 60 meters, with great buttressed bases that can be 10 meters across. The Native Americans of the northwest coast salvaged its long-dead trunks from the swamps and hollowed them into vast canoes and totem poles; and the Haida Indians of the shores of southern Alaska carved arrows from the stems, fashioned the tough knots into fishhooks, and wove the fibers from the bark into ropes, baskets, mats, clothes, and hats. In more humble guise, western red cedar features in suburban gardens, filling the same kind of role as Lawson’s cypress. But the first Thuja to make it to Europe—to Paris, in the sixteenth century—was America’s other native: the smaller T. occidentalis from the eastern states.

  The most widespread of all conifers: one of the many junipers.

  Three more species of Thuja live in northeast China, Korea, Japan, and Taiwan. This is a common pattern of distribution: many trees of many kinds—including oaks—are distributed both in North America and eastern Asia, notably China. They seem for some reason to have found it easy to straddle the Pacific. In any case, trees do not respect political boundaries and, indeed, reveal how arbitrary the lines that we draw on maps really are. Thuja trees in general like it cool and moist, and grow from the coast to the hills. Though most are tall there is one, T. koraiensis, of northeast China and Korea, that grows on exposed mountain ridges as a twisted shrub, showing again that any one group of organisms may essay a great variety of body forms. T. sutchuensis is one of those conifers that was presumed to be extinct but then turned up. To be sure, it didn’t go missing for quite as long as Metasequoia or Wollemia, but it was thought to be long deceased until the late twentieth century, when some were found alive and well in the Daban Shan mountains of northern China.

  The genus Thujopsis has only one species, from Japan, which can look curiously like a plastic imitation of a cypress. It also favors cool, moist places, from the coast to the mountains, and is another conifer that grows slowly at first in shade but eventually overtops its neighbors. Thujopsis comes in various cultivated varieties and is much favored in gardens.

  The four species of Widdringtonia are among the few conifers that put in an appearance in sub-Saharan Africa: in South Africa, Malawi, Mozambique, and Zimbabwe. Widdringtonia are fire-adapted: they do well when the surrounding shrubs are cleared by fire, as happens regularly in the African summer. The genus has been sadly depleted by felling, however. The forests of “Mulanje cedar” on the steep slopes of Malawi’s Mount Mulanje are the only substantial stands of Widdringtonia left to us. They are on my wish list of trees to be seen in the wild.

  Two other genera of the old-style Cupressaceae are worth particular mention. Both have only one species each, both of which can grow into very large trees. They are Platycladus of eastern and northeastern China, Korea, and the Russian far east; and Taiwania, which, of course, occurs in Taiwan and also in China (Yunnan), Myanmar (Burma), and Vietnam—where it was discovered only in this century. It grows up to 70 meters. The businesspeople and diplomats who flock to Taiwan probably feel they have little time for trees. A pity. Perhaps they should make time.

  Of the eight genera that once formed the Taxodiaceae family, five have only one species each: Cryptomeria, Glyptostrobus, Metasequoia, Sequoia, and Sequoiadendron. Of the other three genera, Athrotaxis has three species, while Cunninghamia and Taxodium have two apiece. This gives a grand total of twelve species. Here is a bunch of relicts indeed—magnificent, most of them—but not much left from a group that once bestrode the Northern Hemisphere.

  Cryptomeria japonica, the “Japanese cedar,” known in the trade as “sugi,” accounts for much of the remaining forest in Japan. Yet those forests are probably not natural; rather, they represent the remains of some of the oldest forestry plantations in the world. The timber turns dark green when buried in the ground, to produce jindai-sugi, which serves as a semiprecious “stone.”

  Three genera of redwoods are left to us: the coastal redwood (Sequoia), the giant sequoia (Sequoiadendron), and the dawn redwood (Metasequoia). Truly the remaining redwoods are relic
ts, for 100 million years ago, when the climate was much milder and flowering plants were first coming into their own, there were a dozen more species of redwood throughout western North America, Europe, and Asia. There was even one in Australia. Various species of Metasequoia were widespread in the Tertiary. In the Eocene, around 45 million years ago, when all the world was wonderfully warm, they grew far up in what is now Arctic Canada, only 10 to 15 degrees from the North Pole. But then the world began to cool, in what has been called an “icebox effect”—prompted by a steady diminution of atmospheric carbon dioxide—and by the time of the Pleistocene (around 2 million years ago), the genus almost went extinct. Now, only the dawn redwood is left to us: Metasequoia glyptostroboides. Even this was presumed to be extinct, until a few turned up in central China in the 1940s. It’s hard to say exactly how the last dawn redwoods in the wild have been scratching a living since the time they went missing, because the area around their present habitat has been so cultivated this past few hundred years; but in general they seem to prefer the same kind of niche (wet) as the swamp cypress, Taxodium.

  The genus Sequoia is also reduced to a single species: S. sempervirens, the coastal redwood of western, lowland California and Oregon. Yet the genus was once present in three continents (of which one was Australia). S. sempervirens needs the coast. It gets about a third of its water from the fogs that rise almost daily from the cold currents of the North Pacific and condense against its dark green, leathery, feathery leaves. Some coastal redwoods are managed for timber on a one-hundred-year cycle; their rich reddish brown wood provides everything from telegraph poles to coffins and organ pipes, while the fireproof bark, up to 20 centimeters thick, supplies fiber for fiberboard.