The Secret Life of Trees

by Colin Tudge

  At this point, the story becomes less pleasant. In the 1990s US-based companies began patenting various components of the neem which the many excellent scientists of India had not bothered to do because, under Indian law, such medicinal, natural materials are not subject to patent. Thus the beneficent, sacred neem, rooted deep in Indian soil and Indian culture, has become the subject of squalid legalistic wrangling.

  The Anacardiaceae are a wonderfully distinguished family. Its seventy genera (with 600 species) include some of the finest ornamentals like sumac, Rhus, and the smoke bush, Cotinus, with its round leaves and wispy grey inflorescences. But these tend to be shrubs rather than trees. The pistachio, Pistacea vera, is a bona fide tree, however, up to about 10 metres. It is native to the Near East and Central Asia but has long been cultivated in the Mediterranean and the southern United States for the delectable green kernels of its nuts, eaten as savouries and marvellous in ice cream and its Indian equivalent, kulfi. The cashew tree, Anacardium occidentale, is native to tropical America but is now grown widely in India and East Africa – a very useful crop on land somewhat drier than most fruit or nut trees prefer. Cashews are of course delectable and also nutritionally potent: 45 per cent fat and 20 per cent protein. They are commonly served as nibbles before a meal but in truth, like peanuts, are as rich as any dinner is liable to be. Trees that disperse their seeds with the help of animals must in general attract the animals’ attention and none does so more promiscuously than the cashew. For the nut itself is presented at the tip of a cashew ‘apple’, which is more like a yellowish-reddish pear. The effect is of a sculpture on a plinth, though held upside down on the twig. Some people ferment the ‘apples’ to make kaju, a strong liquor. The shells of the cashew contain an oil that irritates the hands but is also used in industry. I encountered my first cashew tree in Pakistan and although the trip as a whole was memorable, connoisseurs of trees will understand when I say that this was among its highlights.

  But the Anacardiaceae offers yet more tropical delights: the mango, Mangifera indica. The mango originated somewhere in India or Burma but it thrives in all kinds of soil and is now grown throughout the tropics and into Egypt and Florida, often as a street tree (as in large areas of Belém, although you might think Brazil had enough trees of its own), its dark-green, shiny, willow-like leaves providing admirable shade. Often indeed mangoes grow virtually as weeds: I have stood beneath a bus shelter in Panama in a storm while mangoes thudded on the roof, and very acceptable they proved to be. They also provide energy (10 to 20 per cent sugar), and are particularly rich in vitamin A. Nowadays deficiency of vitamin A is a huge issue. Forty million children are believed to be affected, and many are blinded by it (it leads to the drying of the cornea known as ‘xerophthalmia’). Modern biotech companies are using genetic engineering to produce ‘golden’ rice that contains some vitamin A, and are claiming thereby to be socially responsible, not to say heroic. But all dark-green leaves are rich in vitamin A, and all that’s really needed is horticulture – which was always a part of traditional farming; and with a few mangoes or papayas around, the problem is solved. If high-tech vitamin-A-rich rice is ever of help at all, it is only in regions where traditional agriculture has been shoved aside by high-tech, industrialized, monocultural farming.

  Finally, completing this lightning sketch of the Sapindales order and also the Rosid eudicots as a whole, comes the extremely distinguished Sapindaceae family. Like the Malvaceae discussed above (and the Cupressaceae, in Chapter 3) the Sapindaceae family is interesting in its traditional form but has become even more interesting of late as other plants including many fine trees have been included within it. Thus the Sapindaceae family as now described by Judd embraces the old-style Aceraceae (maples), and the erstwhile Hippocastanaceae (horse chestnuts). In the following, in the interests of clarity and of continuity with most extant texts, I will discuss the three traditional families separately. But in the decades to come, I imagine they will all be discussed as Sapindaceae.

  The traditional Sapindaceae family is distinguished enough. It includes about 2,000 species in 150 genera – mostly trees or shrubs but also about 300 climbers (which are of the kind that climb by tendrils, and are often of huge ecological significance). The family is tropical and subtropical, occurring through the tropical Americas, sub-Saharan Africa, India and east Asia, Malaysia and Indonesia, and down into Australia. The family takes its name from Sapindus, which provides oil for soap. It includes some fine fruit trees. The sweet-acid lychee, Litchi chinensis, is from southern China. Botanically the fruit is an aril, like that of yew. A close relative is Melicocca bijuga, grown in America. The rambutan, Nephelium lappaceum, is like a lychee with mad hair. Blighia sapida, named after the unfortunate Captain Bligh of the ill-fated Bounty (who in truth was a distinguished amateur botanist and no mean artist) is known in Africa as the akye, and in the West Indies as the akee. It is the national fruit of Jamaica. Akee is again an aril, which tastes like scrambled eggs when cooked, but is poisonous if plucked at the wrong stage. The Sapindaceae family provides some fine ornamentals, too, like Koelreuteria (a street tree) and Xantboceras (grown for its flowers). The taun tree, Pometia pinnata, from the South Pacific is magnificent at up to 45 metres, with a trunk up to a metre in diameter and a lovely, smooth, reddish fine-grained timber valued for everything from joists and rafters to pianos and the bars of ships’ capstans.

  The Aceraceae, the old-style maple family, includes at least a hundred species in the genus Acer, plus two in Dipteronia. Maples live all over the northern continents, with a huge representation in China, and one in North Africa. This is the field maple, Acer campestre, which is also native to the British Isles and is our only maple. China has scores of native species. Japan has nineteen. North America has about a dozen. Most maples are small to medium-sized but some are large and evergreen, including a few through Malaysia and into Java. As with oaks, we see that in any one genus some species may be evergreen, and some not. Maples are easily recognized for their fruits: paired keys, which spin helicopter-style in the wind, elegantly known in botanical circles as ‘samaras’. In Dipteronia, by contrast, the seeds sit in the centre of a round wing like a yolk in a fried egg. Many maple species produce fine timber, including A. pseudoplanatus, which the British call sycamore and the Americans call ‘plane’. Sycamores in Britain are often magnificent but are commonly perceived as invasive weeds. They are despised in part because they do not support such a wide variety of native insects and other animals as oaks do, for example. But they do support an enormous biomass of insects, which in turn support birds. The British are almost certainly right to despise feral rhododendrons, which really do belong elsewhere, although buzzards like it for nesting. But we should perhaps ease up on the sycamore. Maples are good for other things, too. Sugar maple, A. saccharum, and others are the source of maple syrup, to which it is easy to become addicted. Of the many routes to obesity on offer in the USA, that of maple syrup, crisp streaky bacon and a ‘long stack’ of buckwheat pancakes is perhaps the most seductive of all.

  The Hippocastanaceae is the family of Aesculus, thirteen species of horse chestnuts and buckeyes, widespread in North America, southern Europe and temperate South-East Asia; and of Billia, just two evergreens from Mexico and tropical South America. A. hippocastanutn 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 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 handkerchief tree �
�� named by the children of the British Raj

  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 favoured 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 are grown as ornamentals, and include the bayberry. 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 lies 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.

  Dogwood, Tupelo and the Handkerchief Tree: ORDER CORNALES

  Judd recognizes 650 species of Cornales, in three families, but only the Cornaceae include any significant trees. The family is mostly (though not exclusively) north temperate. Cornus, for which it is named, includes the forty-five 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 first 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 dove tree. All the names suit. I met one in full bloom early one sunny July morning in the University Botanic Garden at Cambridge. 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 twenty-four families, with many outstanding trees, not least in the family Ebena-ceae. 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, which are all 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 US in the late nineteenth century. Native to the US, with smaller, dark red fruits is D. virginiana. This is a tall, thin tree up to 30 metres 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 15–18 metres tall, with trunks around 60 centimetres 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 colour, 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 – door knobs, the butts of billiard cues, chess pieces – and 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 metres) but it yields a fabulous brown-black mottled timber known as Andaman marblewood. In sharpest contrast, America’s native persimmon yields a straw-coloured sapwood that is marketed as ‘white ebony’ (and is also known as bara bara, boa wood, butter wood, possum wood or Virginia date palm). It is used for tool handles, and textile shuttles made from it are said to last 1,000 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 fifty-three 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 seventy 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 favourite. The shea butter tree, is Butyrospermum paradoxum, 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 mould it every which way when it was warm and soft, and it held 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 plantations 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 metres tall, with trunks 2 metres thick. Some have heavy timber, spiked with silica. Other have lighter timber, often free of silica. Among the seventy-five 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 metres tall and 1.2 metres 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 favoured 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 w
ith 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 thirty-two 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 flavour 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 twenty genera include the showy flowers of the Franklin tree, Franklinia; and among the eighty-odd species of the genus Camellia is C. sinensis – tea. It was first grown in China, probably as a tonic, rich in caffeine and essential oils Now it 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 bonsai’d 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, zig-zagged 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 – bonsai’d, 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.