The Tree

by Colin Tudge

  The Hippocastanaceae is the family of Aesculus, thirteen species of horse chestnuts and buckeyes, widespread in North America, southern Europe, and temperate Southeast Asia; and of Billia, just two evergreens from Mexico and tropical South America. A. hippocastanum is “the” horse chestnut: hippo is Greek for “horse” and castanum means “chestnut.” In nature study, children sketch the horse chestnut’s huge palmate leaves, the intriguing horseshoe-shaped scars they leave on the stems, and the big, resinous, scaly buds (or they did when I was at school), and prize their big brown seeds as “conkers.” Grown-ups value them primarily as ornamentals, in many a lovely avenue. Some species of Aesculus, too, are in various ways medicinal, and extracts have been used in North America to stun fish (which seems to emerge as a national hobby); and the wood, light and not durable, is used for boxes and charcoal.

  10

  From Handkerchief Trees to Teak: The Daisy-like Eudicots

  THE SECOND GREAT GROUP of eudicots are the asterids—named after the daisy family, Asteraceae. To be sure, they don’t all look like daisies, any more than the rosids all look like roses. But again, details of their DNA and of their microstructure, particularly the ovules, suggest that the asterids do all derive from a common ancestor—that they form a true clade. The modern taxonomy favored by Judd divides the asterids into ten orders. Three of them contain little in the way of trees, although they do include some shrubs. Thus the order Garryales has a few shrubs from Central America, some of which, including the bayberry, are grown as ornamentals. (Note that, in America, the bayberry is also a common name for members of the Myricaceae family.) The Apiales is named after the family Apiaceae, formerly known as the Umbelliferae, which is best known for carrots, celery, and coriander—but does include the umbrella tree, Schefflera. The Dipsicales includes teasel and honeysuckle, and its greatest claims to arborescence lie with the snowberry, Symphoricarpos, and the elder, Sambucus. But the remaining seven orders between them contain some of the most magnificent and valued trees of all.

  The handkerchief tree—named by the children of the British Raj.

  DOGWOOD, TUPELO, AND THE HANDKERCHIEF TREE: ORDER CORNALES

  Judd recognizes 650 species of Cornales, in three families, but only the Cornaceae includes any significant trees. The family is mostly (though not exclusively) found in northern temperate regions. Cornus, for which it is named, includes the 45 species of dogwood, mostly shrubby. Davidia is the lovely handkerchief tree. It was first reported from the mountains of western China in 1869 by the Jesuit naturalist Father David, who also made the giant panda known to the West, and gave his name to Père David’s deer. Another missionary priest sent seeds of Davidia to Europe thirty years after David found it. Just one seed germinated of the thirty-seven that were planted. It grew into a smallish tree with leaves somewhat like a lime tree—pleasant, yet nothing special. But when it flowered in 1906 Europeans saw for the first time the wonder that had enchanted Father David: for each flower is flanked by two petals as big as your hand that look for all the world like rich, creamy-white leaves. The tree in full bloom is festooned. The children of colonial civil servants in India are said to have given Davidia its common English name, comparing its flowers to the handkerchiefs of the crowds who waved them off from the quay. It is also called the ghost tree or the dove tree. All the names suit. I met one in full bloom early one sunny July morning in the Cambridge University Botanic Garden. Stunning.

  Finally, the ten species of Nyssa are mostly ornamental but include the tupelo, N. aquatica and N. sylvatica, trees big enough to provide North Americans with railway sleepers. (Once Nyssa had its own family, the Nyssaceae, but Judd subsumes it within the Cornaceae.)

  PERSIMMONS, EBONY, CHEWING GUM, TEA, HEATHER, AND BRAZIL NUTS: ORDER ERICALES

  The Ericales order includes around 9,450 species in 24 families, with many outstanding trees, not least in the family Ebenaceae. All the Ebenaceae are trees or shrubs, most from all over the tropics, with just a few from more temperate zones. The major player is the genus Diospyros, with around 450 species: 200 or so in lowland Malaysia; quite a few in tropical Africa; somewhat fewer in Latin America; some in Australia and India; and a few outliers in the United States, the Mediterranean, and Japan.

  Diospyros includes a whole range of edible fruits, all of which are highly astringent until they are fully ripe, but then are delicious. Best known are the persimmons, which look superficially like big, thick-skinned tomatoes and are eaten fresh, cooked, or candied. Most widely cultivated—especially in China and Japan, but also in California and the south of France—is D. kaki from Japan, which was introduced to the United States in the late nineteenth century. Native to the States, with smaller, dark red fruits is D. virginiana. This is a tall, thin tree up to 30 meters and not much cultivated, although its fruits are often picked wild (and D. virginiana is often used as rootstock for D. kaki). The date plum, D. lotus, is grown in Italy and the Far East. D. digyna is the black sapote. Not all the Diospyros fruits are particularly friendly, however: the crushed seeds of some Malaysian and Indonesian species are used to poison fish.

  Diospyros also includes various extremely valuable timbers of the kind known as ebony. The trees are not huge—generally around 15 to 18 meters tall, with trunks around 60 centimeters thick—and so the timber is sold only in short lengths. But the heartwood of some species is jet black, and others are deep, rich brown or alluringly striped in brown or black. For their fine color, strength, and prodigious weight—far heavier than water—the ebonies have been valued since ancient times. The pharaohs had their glossy black furniture made from ebony. It is excellent both for sculpture and for turning—doorknobs, the butts of billiard cues, chess pieces—and for marquetry, piano and organ keys, clarinets, and the chanters of bagpipes.

  Various species are harvested in Africa, where ebonies can be important forest trees, including the very dark D. crassiflora. D. reticulata, from Mauritius, is highly prized. D. ebenum, from Sri Lanka, is known as Ceylon ebony and is often called “true ebony” because its timber is a uniform jet black. D. marmorata from the Andaman Islands is a small tree (only about 6 meters), but it yields a fabulous brown-black mottled timber known as Andaman marblewood. In sharpest contrast, America’s native persimmon yields a straw-colored sapwood that is marketed as “white ebony” (and is also known as bara bara, boa wood, butter wood, possum wood, and Virginia date palm). It is used for tool handles, and textile shuttles made from it are said to last one thousand hours before they wear out. The pale sapwood and the thin dark heartwood are sometimes used together to make a fine veneer.

  The trees and shrubs in the great family of the Sapotaceae bestride the wet, lowland tropics: 1,100 species in 53 genera. Many have edible fruits. The huge genus of Pouteria, with 325 species, includes the mamey sapote, P. mammosa, and the eggfruit, P. campechiana. The 70 species of Chrysophyllum include the star apple, C. cainito, which is also grown ornamentally as the satinleaf. All these sapotaceous fruits are said to be delicious, though the only one I can vouch for personally is the sapodilla, Achras sapota, which has beautiful, barley-sugar flesh. Many tropical fruits are disappointing. Many are fine, but should probably be left for local people to enjoy. But you could munch out on sapodilla; it could well join the banana and the mango as a world favorite. The shea tree is Butyrospermum parkii, the source of an edible oil.

  There is much more to the Sapotaceae. Manilkara zapota is chicle: its latex is the stuff of chewing gum. Several of the 110 known species of Palaquium, especially P. gutta, from Sumatra, Java, and Borneo, yield latex that hardens to form gutta-percha, which is chemically related to rubber (another polymer of isoprene). Nineteenth-century industrial chemists found that they could mold it every which way when it was warm and soft, and it would hold its shape when cool and hard. Soon it was used to fill teeth, make golf balls, and insulate electric and undersea telephone cables. The latex was tapped by cuts in a herringbone pattern, as with rubber, which damaged the wild trees, so plantation
s were established in Java and Singapore. Now, alas, only dentists still make use of gutta-percha, for temporary fillings.

  Many Sapotaceae yield fine timber, too. Some species are big—up to 30 meters tall, with trunks 2 meters thick. Some have heavy timber, spiked with silica. Other have lighter timber, often free of silica. Among the 75 or so species of Sideroxylon is the timber known as buckthorn, ironwood, or mastic. Minusops is marketed as cherry mahogany. The makore (Tieghemella heckelii), from West Africa, is a huge tree up to 45 meters tall and 1.2 meters thick. Its heartwood is a pale blood-red to reddish brown, its sapwood is slightly lighter, and some logs have the mottled, lustrous look of watered silk. It is said by aficionados to have a much finer texture than mahogany, and is much favored for furniture, veneers, and turning; and for laboratory benches, parts of carriages and boats, and for marine-quality plywood. Various species of Palaquium (the gutta-percha genus) and of Payena, from Malaysia and Indonesia, are bundled together under the trade names of nyotah or padang. The timber is deep pink to red-brown, often with dark streaks: again, excellent for furniture and doors and also, outdoors, for shingles to roof or clad buildings like the scales of a fish.

  Finally, the mournful tambalacoque tree of Mauritius, Calvaria major, is from the Sapotaceae. Exactly why it is mournful will be revealed in Chapter 13 (though it apparently has less cause to be downcast than was once thought).

  There is much less to report from the Myrsinaceae family, though it is large enough, with 1,000 species in 32 genera, spread over warm temperate lands and the tropics. The Ardisia genus imposes itself most on human consciousness, with several ornamentals, a few fruits grown in gardens and greenhouses, such as A. crispa; A. squamulosa, used to flavor fish in the Philippines; A. colorata, whose leaves Malaysians take to settle the stomach; and A. fulginosa, which the Javanese boil in coconut oil and use to treat scurvy.

  The Theaceae family, however, is full of interest. The 300 or so species in 20 genera include the showy flowers of the Franklin tree, Franklinia; and among the eighty-odd species of the genus Camellia is C. sinensis—tea. The tree was first grown in China, probably for its tonic, rich in caffeine and essential oils Now tea is drunk by half the people on earth, and grown on the largest scale in India and Sri Lanka, but also in East Africa, Indonesia, and Russia: another of those plants that have transformed the economy and politics of the entire world. C. sinensis left to itself grows into a respectable tree, as tea plantations demonstrate when abandoned—including one I have been told about in Uganda, which was abandoned in the time of Idi Amin and quickly grew into a veritable forest. But in active plantations its tips are picked every fifteen days or so, depending on variety, place, and weather, and in effect it is bonsaied into a hedge, around waist high: a meticulous exercise in topiary. Typically the bushes are grown on steep hillsides (and you really have to go to Asia to see how steep a hillside can be; those classical Chinese painters do not exaggerate). The bushes are brightest green and cover the hills as far as the eye can see, zigzagged with dark narrow gulleys for the pickers. Tea grows best in shade, and among the shade trees grown in Kerala, where I once stayed on a tea plantation, is the Australian silk oak: pruned to filter just the right amount of light, and to provide fodder for buffalo. The landscape is as magical as Alice’s wonderland: bonsaied, topiarized, tessellated, and dotted with trees like feather dusters. Traditional farms, orchards, and plantations worldwide show that beauty and productivity can go hand in hand, and in a crowded world, so they must.

  The Ericaceae family, for whom the whole order is named, is also full of good things. Defined broadly (as Judd does) it now includes 2,700 species in 130 genera of vines and shrubs as well as trees. They grow almost worldwide (although they never made it to Australia—at least as wild plants), especially on uplands and typically on acid soils, relying very heavily on the mycorrhizal fungi in their roots. A few are epiphytes. Some have evolved into parasites and have abandoned chlorophyll. The Scots at the edge of Europe’s tundra know the family mainly for Calluna, the heather, the stuff of purple hillsides. But Calluna is but a windswept northern outlier. The related heaths in the genus Erica are particularly various in South Africa (which has 450 species), and grow to at least head height.

  Where exactly the Ericaceae first arose is not clear, but the Himalayas is a good bet. At least 700 of the 1,200 species of Rhododendron and related Pieris grow where some of the world’s mightiest rivers begin—the Brahmaputra, the Mekong, the Yangtze—and many achieve tree-like dimensions, though since they have many stems they are generally rated as shrubs. There are another 300 species in New Guinea, which are apparently an offshoot of the original Himalayans. Rhododendrons are considered bad news in Britain, where they grow as wild and rampant exotics, though they provide excellent nesting grounds for buzzards.

  Arbutus is the genus of the strawberry tree and of the lovely madrones of North America—with smooth red bark that peels away to reveal yellow-gray beneath. I have walked among madrones in the hills of California, north of San Francisco: they are among the glories of a glorious landscape. Deer and quail enjoy their orange-red fruits. So, too, did the Native Americans. The wood is used locally and makes fine charcoal. Madrones do not grow big, but they can live for at least two hundred years.

  In the Lecythidaceae family are some of the world’s greatest, most intriguing, and most economically important trees. The family includes 400 or so species in 30 genera—of shrubs and vines as well as trees; they are centered in South America but also found in Africa, Madagascar, and tropical Asia. The smallest of all is the eccentric Eschweilera nana, which grows out in the Cerrado and often has an underground trunk like the Attalea palm, a device that protects against fires. Many, however, are emergent trees that grow through the canopy to tower above the rest. Tallest of all are Cariniana micrantha and Couratari stellata, both up to 60 meters. Cariniana and Couratari have the sky to themselves and are pollinated by wind, which is unusual among tropical trees (and among Lecythidaceae). The long, straight boles of Cariniana make excellent timber, and forest hunters tip their arrows with a poison from the bark of Cariniana domestica. Cariniana is the longest-lived of the Lecythidaceae—indeed, of all the neotropical trees. Some have been dated at fourteen hundred years.

  Most striking, however, are the fruits of many of the Lecythidaceae: big wooden globes and cylinders, generally born directly from the trunk, and packed with seeds. The wooden armor has evolved, presumably, to deter predators, although the capuchin monkeys of Amazonia sometimes get the better of it. Sometimes the seeds are big and fleshy and eminently edible, and are dispersed by animals—sometimes by fish. But in some genera (like Carinaria) the seeds are winged like those of an ash and, when the casing breaks, are dispersed by wind. These seeds are too light to carry much nutrient, and to make up for this the seed leaves are green and begin to photosynthesize the moment the seeds germinate.

  Most important by far to human beings is the Brazil nut, Bertholettia excelsa—up to two dozen triangular, desperately hard nuts packed like the segments of an orange within their desperately hard casing. The Brazil nut tree is almost as tall as Carinaria. It can provide good timber, but few would cut it for such a purpose. It’s the nuts that matter: they are 66 percent fat and 14 percent protein—and, more to the point, their flavor is sublime. Europeans and North Americans import about fifty thousand tons of them a year from Brazil and Venezuela, some from wild trees but also from plantations, not least around Belém, at the mouth of the Amazon. The wild trees are protected, and often these days you see them gaunt and abandoned in the middle of nowhere: over vast areas the rest of the forest, which they have evolved to look down upon, has been cleared to make way for sun-stressed cattle and soybeans. Brazil nut trees are very susceptible to fire, and although they are huge they are not long-lived (in contrast to Cariniana). The biggest of them are less than three centuries old.

  The wooden orb that encloses the Brazil nuts has a neat cap at the top, which comes off when the fruit fa
lls to the ground. But the nuts remain trapped: the Brazil nut tree at this point relies upon the good offices of the agoutis, which are long-legged relatives of the guinea pig, to make the hole bigger and carry the seeds away. The agouti eats some of the nuts and buries others for later, just as a squirrel buries acorns (such stashing is a very rodent trick). It doesn’t recover all of them, however, and the seeds that it forgets grow into new trees—though they take twelve to eighteen months to germinate. Thus the Brazil nut tree relies not simply upon the agouti but upon the agouti’s amnesia. The empty Brazil nut cases fill with rainwater and then form nurseries for insects and frogs.

  The Lecythis genus produces sapucaia or paradise nuts, which are said to taste even better than Brazils. I cannot vouch for their excellence; I wish I could. Clearly there is another market here—another economic reason for conserving the Brazilian forest, rather than cutting it down, to add to its aesthetic and ecological advantages. The wooden spheres that enclose the nuts are known as “monkey pots.” Apparently you can catch monkeys by putting a sweetmeat inside an empty pot. The monkey comes along and grabs it, cannot withdraw its closed fist, and refuses to release its booty even when the hunter comes along to bop it on the head. Monkeys are standard fare for the people of tropical forests. Lecythis pisonis, of Amazonia and the Brazilian Atlantic forest, has the largest fruits of all the family: it takes them about a year to grow as big as your head. The fruit opens while still on the tree to reveal seeds that are each coated in a bright fleshy aril. On the same night that the fruits open, the seeds are dispersed by bats. The efficiency both of animal pollination and seed dispersal can be staggering: coevolution really works. The flowers of L. pisonis are pollinated by carpenter bees, which are among the biggest bees of all (even bigger than bumblebees). L. grandiflora yields a much-valued timber marketed as wadadura.