I grew up near the Royal Botanic Gardens, Kew, London. My parents, an engineer and a speech therapist, shared a passion for plants and they inspired my brother and me with beauty and botany. This tree was used for deadly poison, that one for chocolate, another to insulate the communications cables that criss-cross the Earth. Here was a species with flowers that change colour when they are pollinated. We used all our senses: a lick of latex from an opium poppy was particularly entertaining, mostly for the look on friends’ parents’ faces when we told them. Virtually every story about a plant was part of a wider one about animals or people. I learned about the horror of the slave trade when my father gave me a tiny piece of Dieffenbachia, known in the United States as ‘dumb cane’ for the effect it had on the tongues and throats of plantation workers who had been too vocal about their lot. Those visits left me with a lasting interest in plants and their relationships with people, although I don’t think anyone told me what a tree actually was. We just knew them when we saw them.
After a career that included making science documentaries, I found myself returning to Kew, this time as a trustee. I also joined the boards of the Woodland Trust and the Eden Project, and the Council of Ambassadors of the World Wide Fund for Nature, all organizations that engage the public with the natural world. I soaked up the expertise around me and combined it with my own experience. Several TED talks and 3 million views later, I realized that there is public interest in plant stories that cross disciplines – hence my urge to write Around the World in 80 Trees.
The world’s trees are astonishingly diverse – we now know that there are at least 60,000 distinct species. Unable to run away from animals that would love to eat them, they manufacture unpleasant chemicals as a deterrent. They exude gum, resin and latex in order to swamp, poison and immobilize insects and other attackers, and to exclude fungi and bacteria. Those defences give us chewing gum, rubber and the world’s longest-traded luxury good, frankincense. Trees, such as the alder, which have adapted to live in wet places, have wood that resists rotting in water. The city of Venice was literally founded on such trees. Trees did not evolve to satisfy human demand, however. Over millions of years they adapted to environmental niches, to defend themselves and to ensure the survival and dispersal of the next generation. The best adapted bore more progeny and spread.
Being rooted to the ground, trees have an inexorable link to the habitat in which they grow, and every location forges different relationships among landscape, people and trees. Lindens (or limes) and beeches look familiar to a British eye, but the German affinity with those same trees has a nearly mythic quality. In the hot, dry conditions of southern Africa, baobabs go to extraordinary lengths to find and conserve water, and under a frazzling Middle Eastern sun, being able to slake one’s thirst from a pomegranate fruit bursting with juice is laugh-out-loud special. In its native and biodiverse boreal habitat, the Dahurian larch reveals unusual adaptations to the cold, while the humid warmth of rainforests supports elaborate relationships, such as that between the Malaysian durian and the bat. Many Australian species, such as the Eucalyptus genus, secrete resins and essential oils that protect them against herbivores, while the trees of Hawaii, which lacks native grazing mammals, have had less need to develop spines and unpleasant chemicals. In Canada, the climate causes maple leaves to mount a gorgeous autumn display of colours. Back in Europe, the same species appears drab in comparison.
There was a whole world in that tree, and so there is in every tree. They warrant our appreciation, and many of them need our protection
The range and variation of trees form only one way of thinking about their incalculable value. One of my earliest memories is of a spectacular cedar of Lebanon, near our home. One winter morning we found it dead, its trunk and limbs strewn haphazardly and being sawn up. It had been struck by lightning. That was the first time I saw my father cry. I thought about the huge, heavy, beautiful thing that was hundreds of years old and that I had thought invincible, and wasn’t, and my father, who I had thought would always be in benign control of everything, and wasn’t. I recall my mother saying that there had been a whole world in that tree. I remember puzzling over that.
My mother was right. There was a whole world in that tree, and so there is in every tree. They warrant our appreciation, and many of them need our protection.
London Plane Tree
With large maple-like leaves and towering height, the London plane is a tree of pomp and circumstance, a symbol of a nation at the height of its powers. The branches begin high up the trunk so that mature trees have a lofty, architectural quality, giving plenty of shade without restricting the view at street level. Planted throughout London in the nineteenth century to complement the city’s imposing squares and thoroughfares, the plane was the ideal symbol for the capital of a growing empire. Visitors, watching in awe and envy at state processions along plane-lined boulevards between Parliament and Buckingham Palace, would have got the message: here was the centre of a powerful, industrialized country, stable and confident enough to plan a century ahead, where even the trees were incorruptible. How British.
The London plane is not merely an immigrant but one of mixed parentage…
Except that the London plane is not merely an immigrant but one of mixed parentage: the multiplication sign in the scientific name denotes a hybrid, in this case between the American sycamore and the Oriental plane, which is native to southeastern Europe and southwestern Asia. Introduced by plant-hunters, the two trees probably met and mingled towards the end of the seventeenth century, although there is debate about whether this was in England, Spain or – quelle horreur! – France.
The London plane is an excellent example of heterosis, or ‘hybrid vigour’, whereby the offspring of two species or varieties that have each been isolated and inbred can show remarkably increased vitality and strength. The London plane was just such a cross and embraced with enthusiasm the burdens of city living.
In the heyday of its planting, the plane grew up alongside pumps and factories – the nineteenth-century engines of Empire. But the Industrial Revolution, which harnessed steam power, also left London black with soot. Few species could survive such insult, but the London plane is especially well adapted to urban life, having a special trick that helps it thrive in polluted air. Its bark is brittle and, because it cannot adapt to the fast growth of the trunk and branches underneath, it drops off in flakes the size of a baby’s hand. The pleasingly random dappling left behind on the trunk resembles army camouflage and represents a critical part of the tree’s defence. The bark of the London plane, like that of many other species, is dotted with tiny pores, a millimetre or two across, called lenticels, which allow the exchange of gases. If these become clogged, the tree suffers. The ability of the plane to slough off a layer of grime that it has removed from the atmosphere helps to keep both this city-dweller and its human companions healthy.
Today, the London plane makes up more than half of London’s trees. Berkeley Square has the most impressive specimens (planted with remarkable foresight in 1789 by a local resident), but there are plenty of others, lining the Thames riverside, populating the city’s magnifi cent royal parks and serving as the city’s shade and lungs. Town planners from around the world have had plenty of opportunity to consider the advantages of the tree for their own cities, and what was originally an almost exclusively London phenomenon has spread across the temperate world. Paris, Rome and New York have gained, at the expense of London’s uniqueness.
But even this most stately of trees is not always dignified: in autumn and winter, dangling pairs of seed-balls festoon it, creating quirky silhouettes that pander to smutty schoolboy humour. The pom-poms also provide food for birds and the raw material for itching powder. On a sweltering July afternoon, though, London’s planes are a glorious and imposing spectacle and a reminder of a time when this was the centre of the world.
Figs are the fruit of desert orchards. With deep roots, famously able to seek out water, they can also insinuate themselves into crevices and sprout from walls. They can grow as straggly bushes or as trees up to 12 metres (40 feet) high with smooth, elephant-grey bark. Leafless in winter, their broad, rough-to-the-touch leaves appear in late spring, just when people and animals start to need the shade.
Despite the best efforts of painters over the centuries, fig leaves are generally too deeply lobed to have reliably covered the nakedness of Adam and Eve. However, the fi g and its fertility-related stories have featured in all the cultures of the Middle and Near East, where it has been cultivated for at least 4,000 years. Appropriately, the botanical story of the fi g is one of sex and gender.
The fig ‘fruit’ itself can be male or female and is a fleshy, hollow flask, lined on the inside with a thick carpet: a mass of tiny florets. (This container is called a syconium, after the Greek sykon, meaning fig; the word ‘sycophant’ is from the same root and probably referred originally to ancient do-gooders who informed on anyone illegally side-stepping an export ban on the fruit.) There are two kinds of fi g tree. Female trees, with female flowers, bear the juicy fruit that we eat. Male trees bear dry, inedible ‘caprifigs’, in which some of the flowers are male and some female. (Caprifigs take their name from goats – the only creature that will eat them.) The challenge is to get the pollen from male flowers inside the fig on the caprifig tree over to the female flowers, which are inside the fruit growing on a female tree.
Even before a female wasp emerges, a male wasp will mate with her, then burrow his way out and die
The flowers of most trees are either wind-pollinated or gaudy and sufficiently sweet-nectared to attract pollinators, which deliver pollen efficiently straight to the female parts of a fl ower. Members of the Ficus genus do things differently: each species relies on a specific wasp for pollination. The Blastophaga wasps that pollinate F. carica, the common edible fig, are female, stingless and tiny – just a couple of millimetres long. The way they do it is deliciously baroque. Wasps of both genders hatch inside the male caprifigs. Even before a female wasp emerges, a male wasp will mate with her, then burrow his way out and die. At this stage, the male flowers inside the caprifig produce pollen. After a brief rest, the female makes her way out of an exit hole made by a male wasp, dousing herself in pollen as she goes. Guided by scent, she flies off in search of another fig, in order to lay her eggs. When she finds one, she squeezes through the little hole at the base of the fi g, stripping off her wings and antennae in the process. If she happens to have entered a caprifig, she lays her eggs, which will eventually hatch to continue the cycle. But if she enters a female fig, she will discover that she has been conned. Although she wanders from floret to floret, spreading pollen as she goes, the flowers in the female fig won’t fit her anatomy; she cannot lay her eggs. The flowers are pollinated and scores of tiny seeds develop, but there will be no wasp larvae. The female wasp is doomed, and enzymes in the plant gradually digest her. The female fig swells and sweetens, attracting bats and birds – and humans – to spread its seeds; a laxative ensures that seedlings get a nutritious start.
Some fig varieties have been bred to be parthenocarpic, meaning that they don’t require pollination. However, in Turkey, which is the biggest producer of figs, the most historically popular and by consensus the most delectable fi g variety is the Smyrna, named after the Turkish Aegean coastal region now known as Izmir. This variety, as well as its Californian derivative the Calimyrna and others famed for their flavour, is proudly wasp-pollinated. Early attempts to grow the Smyrna fi g in the United States ended in failure because growers initially dismissed as baseless mumbojumbo the Middle Eastern peasants’ tradition of hanging branches of caprifigs in their orchards, but in fact it is a well-observed encouragement to wasps to act as sexual go-betweens.
This extract is taken from Around the World in 80 Trees by Jonathan Drori and illustrated by Lucille Clerc
Want more great Boundless content in your inbox every Sunday? Sign up to the free, weekly newsletter, here.