by Colin Tudge
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 climbers 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 Yangtse – 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-grey 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 200 years.
In the Lecythiidaceae family are some of the world’s greatest, most intriguing, and most economically important trees. The family includes 400 or so species in thirty genera – of shrubs and climbers as well as trees; centred in South America but also found in Africa, Madagascar and tropical Asia. Smallest of all is the eccentric Eschwei-lera 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 metres. Cariniana and Couratari have the sky to themselves and are pollinated by wind, which is unusual among tropical trees (and among Lecythiidaceae). 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 Lecythiidaceae – or indeed of all the neotropical trees. Some have been dated at 1,400 years.
Most striking, however, are the fruits of many of the Lecythiidaceae: big wooden globes and cylinders, generally born directly from the trunk, and packed with seeds. The wooden armour has evolved, pre-sumably, 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, Bertbolettia 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 per cent fat and 14 per cent protein – and, more to the point, their flavour is sublime. Europeans and North Americans import about 50,000 tons of them a year from Brazil and Venezuela, some from wild trees but also from plantations, not least around Belem 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: the rest of the forest, which they have evolved to look down upon, now cleared to make way for sun-stressed cattle and soya. 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 falls 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 blip 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: co-evolution really works. The flowers of L. pisonis are pollinated by carpenter bees, which are among the biggest bees of all (even bigger than bumble bees). L. grandiflora yields a much-valued timber marketed as wadadura.
Cannonball fruits grow straight from the trunk
The wooden fruits of Couroupita guianensis grow straight out from the trunk and may be 20 centimetres across, giving it the name of ‘cannonball tree’. The fruits break as they hit the ground to expose a bluey-green pulp, packed with hairy seeds. To people the pulp smells foul but peccaries (American wild pigs) love it. The seeds, or some of them at least, pass right through the peccary, apparently protected from its digestive juices by their hairiness, and may germinate in the dung. The pulp of cannonball trees is also fed to domestic pigs and poultry. The cannonball tree is often grown as an ornamental: its intriguing fruits follow a show of large, waxy, sweet-smelling flowers.
Also grown as ornamentals are species of Barringtonia, the most important genus from the Old World. Careya, of Malaysia and India, gives useful timber known as tummy wood.
Nightshade, Borage – and Some Very Fine Trees: ORDER SOLANALES
It isn’t a hundred per cent clear that the Solanales do form a coherent group, a true clade. For the time being, however, the order is taken to include around 7,400 species of herbs, shrubs, vines and trees in six families, of which three are of particular interest.
The Solanaceae are the family of potatoes, tomatoes, capsicums and aubergines. All are pharmacologically potent, at least in the wild form: wild potatoes and tomatoes are generally poisonous. Also in the family, as if to rub the point home, are tobacco, mandrake and the nightshades. The shrub jimsonweed (Datura) provides steroids that are used to prepare oral contraceptives. Only a few Solanaceae are trees, however. I have seen some of them out in the Cerrado. Attractive, but not large.
The family Boraginaceae m
ay or may not belong among the Solan-ales. Its position, says Judd, is ‘somewhat problematic’. In any case it includes 2,650 species in 134 genera of herbs (including borage and comfrey), climbers and shrubs both tropical and temperate – and some very convincing and commercially significant trees. The 320 or so known species of the genus Cordia include C. abyssynica and C. millenii from East Africa, and C. platythyrsa from West Africa, all marketed as ‘African cordia’, though all have euphonious local names as well. They grow up to thirty metres, and up to a metre thick. The bole has an irregular shape but the sapwood is a pleasant cream and the heartwood is golden brown, and although it is weak and soft it is good for decorative trimmings, like the edges of shelves in libraries, and for veneers. More to the point it resonates well, and is favoured for drums and sounding boards; and the people of West Africa make boats from cordia. Brazil has its own Cordia: C. goeldiana, known as freijo (or in Brazil as frei Jorge) and also, in the US, as cordia wood or jenny wood. Some species of Cordia live around the coast, and their corky seeds are dispersed by water.
Coffee, Quinine and Some Excellent Timber: ORDER GENTIANALES
Within the Gentianales order are four families containing about 14,200 species, with many excellent and important trees. The very large family of the Rubiaceae contains around 9,000 species in 550 genera. Most live in the tropics and subtropics, and most of the tropical species are trees or shrubs. They include many fine ornamentals, notably the much-valued Gardenia, some of which are trees in the wild. Most important by far of the many Rubiaceae that are pharmacologically significant is the genus of coffee, Coffea. C. arabica produces the best quality coffee, and is traditionally grown in tropical America, notably Brazil; while C. canophora yields ‘robusta’ coffees which are generally less fine, but higher yielding, and have been largely grown in Africa and Asia. Coffee is grown in various ways but the quality is finest when the bushes are grown in shade, because then the fruits mature more slowly; the shade trees can be of many kinds but often leguminous types are grown which yield excellent fodder as a bonus. Everyone should do well out of coffee, but thanks to modern globalized trading laws all farmers in the tropics just about everywhere are now being exhorted to grow more and more of it – in places like East Timor and Vietnam as well as the traditional countries – so now there is world glut: prices fell by nearly 70 per cent in the five years up to 2004. Farmers borrow from banks or sometimes from moneylenders to start their coffee plantations, then find themselves selling for less than the cost of production, and go bust (I have seen the failing plantations in eastern Brazil). Myth has it that the consumer benefits from their misery but high street prices have not dropped noticeably and in truth the only beneficiaries are the traders. ‘Twas ever thus, it seems.
Several species of Cinchona were also of great pharmacological significance as the source of quinine, for a long time the front-line drug against malaria, much favoured by the British colonialists. Whether the British obtained the rubber tree from Brazil by underhand means is somewhat arguable, but the removal of cinchona seeds from Bolivia in the nineteenth century was explicitly against Bolivian law. This seed founded the Javanese quinine industry, which dominated the world’s trade until 1939.
The Rubiaceae family also provides some fine timbers. Abura (Mitragyna ciliata) of the west coastal swamps of tropical West Africa grows to 30 metres and provides a pale-yellow to pinkish-brown timber, excellent for mouldings and floors, and also used to encase accumulators (batteries) because it is resistant to acid. Even taller, at around 50 metres, is the opepe, Nauclea diderrichii. Its creamy-pink sapwood and golden-yellow heartwood are valued both for their looks – for furniture, floors, turnery, veneers – and for rough work outside, from jetties to railway sleepers. Degame, Calycophyllum candidissi-mum, from Cuba, Mexico, Venezuela and Colombia is smaller than its African cousins (up to 20 metres tall) but again excellent for sculpture, turnery, furniture and floors.
The Apocynaceae family is again big and highly various, with around 3,700 species of trees, shrubs, climbers and herbs in 335 genera, again mainly tropical and subtropical with just a few in temperate lands. Most of the genera contain poisonous species which, as is the nature of things, are often converted to valuable drugs – none more so than the Madagascar periwinkle (Catharanthus) source of some of the most effective drugs against leukaemia, and Rauvolfia, which provides a drug that’s used to treat hypertension. But the Apocynaceae also include some pleasant and quaint ornamentals including periwinkle (Vinca), oleander (Nerium) and the carrion flower (Stapelia), a peculiar worm-like succulent whose evil smelling blooms are pollinated by flies and yet is beloved of collectors (among whose ranks I once was, and perhaps will be again). The trees of the Apocynaceae, all tropical, are often huge and impressive. The genus Dyera includes D. costulata of Malaysia and Indonesia, known as jelutong. It stands up to 60 metres tall and yields creamy timber that matures to the colour of straw, excellent for sculpting and carving, not least of wooden clogs. It also yields a latex that is extracted for chewing gum – and the process of extraction commonly leads to fungus infection that colours the timber which, as in beech, or indeed in blue cheeses, can increase its value. Species of Aspidosperma from south-eastern Brazil are marketed as rosa peroba. The trees stand around 15 metres tall; the sapwood is creamy yellow, the heartwood rosy red, hard, heavy, very dense, and used for everything from building ships to parquet floors, turnery and very beautiful veneers.
Best known of all the trees of the Apocynaceae, however, is the frangipani, Plumeria rubra, alias the temple tree or pagoda tree, sometimes growing as a small tree up to 6 metres and often as a large bush. The frangipani was imported to India from its native Jamaica, Mexico and Ecuador. Mrs Cowen, in Flowering Trees and Shrubs of India, writes that with its ‘pale swollen limbs the tree is in itself no thing of abundant beauty’. But ‘It claims affection for its sweet-scented flowers which, nearly throughout the year, open, bloom, and fall to lie immaculate on the earth beneath. To both Buddhists and Mohammedans the tree is an emblem of immortality because of its extraordinary power of producing leaves and flowers after it has been lifted from the soil. For this reason it is frequently planted near temples and in graveyards, where daily the fresh, creamy blooms fall upon the tombs. Hindus make use of the flowers in worship and they are frequently given as votive offerings to the gods.’ Frangipani finds many uses in medicine and its yellow-brown and reddish timber, though it comes only in smallish pieces, is easily worked.
Among the 970 or so species (in 84 genera) in the Gentianaceae are the gentians for which the whole family and order are named. These are not trees, but ornamental herbs. Some members of the family are extreme parasites with small leaves and no chlorophyll (showing once again that flowering plants have a considerable predilection for parasitism). Some are pleasant shrubs. Many provide medicines and flavourings. But there would be precious few significant trees among the Gentianaceae were it not that the Loganiaceae, which is the last family of the Gentianales, has recently been re-examined and reorganized. So the tropical Asian genus Fragraea has been transferred to the Gentianaceae from the Loganiaceae, where it traditionally resided: and Fragraea includes some significant timber trees, one of which (F. fragrans) has particularly huge flowers and is also planted as an ornamental. The plants that remain in Loganiaceae include nothing that need occupy a book on trees.
Olive, Ash, Jacaranda and Teak: ORDER LAMIALES
Taxonomists have got seriously stuck into the Lamiales this past few years. The order has grown: it now embraces the traditional order Scrophulariales, which included the antirrhinums and foxglove; and subsumes the old Bignoniales, which contains some magnificent trees as will shortly be described. In addition, there has been much chopping and changing of genera between the different families that made up the original three orders that are now included within the Lamiales. I will not go into details because most of the changes do not involve trees – and I am mentioning all this only to provide continuity with trad
itional texts. (If you read Heywood, for example, as everyone should, you will find the order Scrophulariales, and might be wondering what happened to it if it wasn’t mentioned here.)
The new-style, expanded Lamiales now includes 17,800 species in twenty-four families. Nineteen of those families contain mainly herbs, some of which are parasitic, like the serious tropical weed Striga and the temperate wayside broomrapes, Orobanche. There are many epiphytes (notably in the African violet family, Gesneriaceae) and also some vines and shrubs (the garden favourite Buddleia has been imported into Lamiales from its former position among the Gen-tianales), but at best these families include only a few small trees. Among five of the Lamiales families, though, there are some very significant trees indeed.