A field guide to a book about trees
How trees drink, breathe, grow tall and grow old — the natural history of trees, told from the floor of a tropical rainforest.
A friendly summary of “Trees: Their Natural History” by Peter A. Thomas (Cambridge University Press),
rooted in the rainforest of Bukit Timah and the trees of Singapore.
Descend into the canopy ↓
The book in a nutshell
We walk past thousands of them without a second glance. Yet a tree is one of the most extraordinary machines on Earth: a living tower that makes its own food from sunlight, hauls water dozens of metres into the sky with no pump, and can keep going for centuries. Peter Thomas set out to answer the simple questions we never think to ask.
Cambridge University Press · 2nd edition
Peter A. Thomas is a forest ecologist at Keele University. His book is loved because it explains the deep biology of trees in plain, playful language — every chapter can be read on its own, and every page hides a surprising fact from a forest somewhere in the world.
There is no pump inside a tree. Water is pulled upward in an unbroken thread, dragged by leaves losing water to the air — a straw kilometres long that never sips.
A century-old tree could have dozens of orders of branching. Instead it keeps only a handful — most buds simply never grow, so light can still reach the leaves.
Just under the bark sits a paper-thin living layer, the cambium, adding a fresh sleeve of wood each year. The bark must split and stretch to keep up.
How a tree works
Thomas builds the book around the tree itself — leaves, trunk, roots and seeds — then asks how each solves the puzzle of staying alive. Here is the whole tree in four movements, plus the tough business of surviving.
The food producers
Leaves are solar panels. They catch sunlight and turn air and water into sugar — the tree's food — while breathing out the oxygen we live on. Their green is chlorophyll doing the work.
Did you knowEvery pore on a leaf is a gamble: open to feed, and the tree loses water; close to save water, and it goes hungry.
More than a drainpipe
The trunk is scaffolding and plumbing. Wood carries water up from the roots; a separate layer carries sugar down from the leaves. The rings you count are years of growth stacked like sleeves.
Did you knowMost of a trunk is dead. Only a thin living skin around the outside is actually alive and growing.
The hidden tree
Half the tree is underground and out of sight — anchoring it, drinking water, mining minerals. Most roots trade with fungi in the soil, swapping sugar for nutrients in a vast secret network.
Did you knowRoots spread wide and shallow far more than they plunge deep — a tree stands like a wine glass on a saucer, not a nail.
The next generation
Flowers are how trees flirt — with wind, bees, birds and bats. A seed is a packed lunch and a set of wings, engineered to land somewhere its parent's shade won't smother it.
Did you knowRainforest trees often bribe animals with sweet fruit to carry their seeds far away for free.
Living in a hostile world
A tree cannot run, so it fights chemically: bitter bark, sticky resin, walls sealed around wounds. It weathers drought, fire, storms and hungry insects — sometimes for hundreds of years.
Did you knowTrees don't die of old age so much as of accumulated damage — they simply run out of ways to keep repairing themselves.
Trees & us
The final chapter turns to people: timber, fruit, medicine, shade, shelter and clean air. Our cultures grew up under trees — and their future now depends on ours.
Did you knowA single large rainforest tree can be a whole neighbourhood — home to hundreds of other plants and animals at once.
Into the tropical rainforest
Thomas shows that no two trees compete on a level playing field — a forest is stacked into layers, each with its own light, air and residents. Nowhere is this clearer than in a lowland tropical rainforest like the one at Bukit Timah, one of the last patches of ancient forest in Singapore. Hover or tap a layer to explore it.
A tiny reserve, an enormous inheritance Bukit Timah covers just 0.2% of Singapore's land, yet it shelters around 40% of the nation's native plants — over 840 kinds of flowering plant crowded into 163 hectares. It is the only hill dipterocarp forest in the country, and one of very few city-centre primary rainforests anywhere on Earth.
Field guide · Bukit Timah Nature Reserve
This forest is ruled by one great family: the dipterocarps — the "two-winged fruit" trees whose seeds spin down like helicopters. They build the towering skyline of the reserve. Around and beneath them grows a riot of figs, palms, climbers and ferns.
↳ 18 dipterocarp species live here · the tallest emergents reach 30–60 m · established 1883, Singapore's oldest reserve
Shorea curtisii
The seraya is the signature tree of Bukit Timah, crowding the drier ridge-tops where few others thrive. From a distance its crown looks like a giant grey-green cauliflower floating above the forest. One seraya here is thought to be around 360 years old — among the oldest living things in Singapore, a sapling long before the island was a city.
Dipterocarpus caudatus
A soaring forest giant whose seeds carry two or three papery wings. They twirl to the ground and germinate almost at once, racing to root before the leaf litter smothers them.
Shorea & Anisoptera spp.
More members of the meranti clan that make up the reserve's high canopy. For centuries their prized timber built houses and boats across the region — which is exactly why so little primary forest survives.
Parishia insignis
One of the true emergent giants of the reserve and a listed Heritage Tree — protected, health-checked and even fitted with a lightning conductor to help it weather the storms of another century.
Ficus spp.
Figs are the forest's great feeders — their fruit sustains birds, bats and monkeys year-round. Each fig is pollinated by its own tiny wasp in one of nature's neatest partnerships. Some figs begin life high on another tree and slowly wrap it in a living cage.
Macaranga spp.
The forest's first responders. When a giant falls and light floods in, fast-growing macarangas rush to fill the gap, sheltering the slower giants that will one day overtake them.
Calamus & Daemonorops spp.
Climbing palms that hook and scramble their way up to the light rather than build their own trunk. They armour themselves in vicious spines — and give us cane furniture.
Licuala · Platycerium · Asplenium
The shady understorey belongs to fan palms and to over 80 kinds of fern. Staghorn and bird's-nest ferns perch high on trunks, catching falling leaves to compost their own private soil.
Field guide · beyond the reserve
Step out of the forest and the trees keep going — shading pavements, arching over expressways, standing guard in parks. Many were planted to turn a hot young city into a Garden City. These are the ones you'll meet on any ordinary day.
Cyrtophyllum fragrans
Singapore's unofficial national tree, native and slow-growing, with wood so hard that termites give up. The famous low-slung branch of the tembusu at the Botanic Gardens is drawn on the back of the S$5 note — you carry one in your wallet.
Samanea saman
The great umbrella that shades Singapore's roads — surprisingly, an immigrant from tropical America. Its leaflets fold up before rain and again around five o'clock, earning the Malay name pukul lima, "five o'clock". Ferns and orchids ride on its mighty arms.
Pterocarpus indicus
A fast-growing giant that greened the city in a hurry. Once a year it erupts in fragrant yellow blossom that lasts a single day — bloom in the morning, a golden carpet on the ground by the next.
Peltophorum pterocarpum
A tough, sun-loving native whose whole crown lights up with fragrant yellow blossom. Its love of heat and drought makes it a natural survivor of the Singapore roadside.
Adenanthera pavonina
A roadside shade tree with a secret treasure: pods that split to reveal glossy, perfectly scarlet seeds. Generations of Singaporean children have collected them by the pocketful.
The city's living monuments
Over 200 exceptional mature trees are protected under Singapore's Heritage Tree Scheme — nominated by the public, health-checked by arborists ("tree doctors") and shielded from lightning. Any giant with a trunk over five metres around can qualify.
A quiet fact hiding in plain sight — half the map of Singapore is named after trees:
Trees & us
Peter Thomas's book ends where it began — with wonder. The best way to feel it isn't to read about a tree at all, but to walk into a forest, look straight up, and realise how little we notice the giants we live among. Bukit Timah is fifteen minutes from the city. Its oldest tree was already ancient before Singapore had a name.