Kingdom of Plants: Survival
A cactus that flowers for one night a year. A plant that hides underground and looks at the sun through windows in its leaves. A shrub that waits 40 years, flowers once and dies. In the desert glasshouses and the deep-frozen vaults of Kew, David Attenborough meets the plants that survive the harshest places on Earth and the people making sure none of them is lost.
How Can a Plant Survive Where It Almost Never Rains?
From the morning fog. Under a microscope its skin is covered in thousands of tiny jagged points. When sea fog drifts in at dawn, droplets condense on them and trickle down to the plant. Its round, ball-shaped body holds as much water as possible for the smallest surface to lose it from.
A tiny cactus called Blossfeldia. David Attenborough calls it the only flowering plant that can dry out completely for months on end. Give it a shower of rain and it comes back to life and produces a little flower. Waiting for the right moment is the trump card of many desert plants.
Put Your Instincts to the Test
Desert plants have had millions of years to solve the problems of heat, drought and hungry animals. Pick an answer for each question, then see if your instincts were right.
Huge, bright flowers and a powerful scent. Its blooms usually open on a night of the full moon, the biggest and brightest around, with a nectar feast for night-flying animals such as bats. By morning the petals have closed, wrapping the newly pollinated seeds and locking their moisture inside.
Through windows in its leaf tips. Only the flat ends of its leaves poke above the sand. Each contains a clear patch that works like a lens, letting sunlight shine down through the leaf to the green cells inside, while the rest of the plant stays cool and moist underground.
It calls in the ladybirds. Each bite makes the pine release more scent, which sets off other branches and even other trees, until a whole forest is cloaked in it. Eyed ladybirds follow the trail as surely as sharks follow blood and eat the aphids. The ladybirds get a meal and the tree gets rid of its pests.
Understanding the Science
Tap each card to see how plants cope with heat, drought and hungry animals and how Kew is protecting them.
Key Concepts
Living by Night
Tap to learn moreIn deserts where midday can reach 50°C, many plants do little in the heat of the day and become active in the cool of the night. Night-flowering cacti are pollinated by bats, which can drink one and a half times their own weight in nectar in a night. In Mexico the flowers open along the route the bats take each spring, a nectar corridor across the desert.
Storing Water
Tap to learn moreLeaves are thin with a large surface, so they lose a lot of water. Many desert plants have done without them: the green pigment moves to a thick, swollen stem that stores water. Pleats in the stem open out after a storm so it can soak up as much as possible while it lasts. Some stems are almost round, because a sphere has the smallest surface for its volume.
Keeping Water In
Tap to learn moreThe old man cactus is covered in thick white hair, which shades it and traps still air around its stem so less water evaporates. Others have a thick waxy skin. Pine needles are another answer: in winter, when water in the ground is frozen, tough narrow needles lose very little. Every one of these is a way of slowing down water loss.
Waiting for Rain
Tap to learn moreMany desert plants survive months or even years of drought by slowing their life almost to a stop. When rain finally comes they spring back: the resurrection plant, a spike moss from Mexico, uncurls within hours. Desert flowers then burst out in brilliant colours, because they must attract pollinators and set seed before the ground dries out again.
Grow Slowly, Flower Once
Tap to learn moreAn agave can spend 40 years or more storing food and water in its fat leaves. Then it puts everything into one huge flower stalk that grows a quarter of a metre a day, so tall that Kew has to take panes out of the glasshouse roof. Its bright flowers at the top attract hummingbirds, which hunt by sight. Having flowered once, the century plant dies.
Defences
Tap to learn moreA plant full of water is tempting to thirsty animals. Some defend themselves with long, strong spines against grazers such as llamas. Living stones from Africa are camouflaged to look like the pebbles around them and even change colour to match the local rock. Others fill their sap with chemicals that animals find nasty.
Chemical Warfare
Tap to learn morePlants also fight each other with chemicals. Eucalyptus trees make so much oil that it can hang over a forest as a blue haze. When their leaves fall and rot, the oil soaks into the soil, and the roots add more. It stops the seeds of other plants from growing round the tree's base, so the eucalyptus faces less competition for water and light.
Seeds: Time Capsules
Tap to learn moreA seed is a young plant with a packed lunch inside a tough coat. It can wait, dormant, until conditions are right, sometimes for centuries: seeds of a South African pincushion plant captured at sea in 1803 grew at Kew 200 years later. Kew's Millennium Seed Bank cleans and dries seeds, seals them in jars and keeps them at minus 20°C, so that no plant need be lost for ever.
Try It: Design a Desert Plant
Click the cards to design a plant, then put it through a desert year of scorching days, rare storms and hungry llamas. Can it survive and make seeds for the seed bank?
Every choice is a trade-off. Big leaves make lots of food but lose water fast; a fat, pleated stem holds water and swells after a storm, but it's tempting to grazers; wax and hair slow down drying; spines and camouflage put grazers off. Real desert plants have each found their own balance, and Kew keeps seeds of thousands of them frozen in case they're ever lost from the wild. A year here takes a minute.
Wildlife of the Dry Zone
Meet some of the toughest plants on Earth, from Kew's desert house and seed bank, along with an animal or two that depends on them.
Queen of the Night
Tap to learn moreA scruffy-looking Mexican cactus for 364 days a year. On one night, usually at full moon, it opens enormous white flowers that glow in the moonlight and fill the air with scent. Bats and moths come for the nectar. By morning the flowers have closed for ever.
Nectar Bats
Tap to learn moreEvery spring, 100,000 pregnant bats fly about 1,600 kilometres (1,000 miles) across the desert from central Mexico to caves in Arizona. They feed on night-flowering cacti all the way and later spread the cacti's seeds in their droppings. David Attenborough calls them cactus farmers.
Old Man Cactus
Tap to learn moreA tall Mexican cactus wrapped in long white hair, like an old man's beard. The hair shades the stem from the fierce sun and traps a layer of still air against it, so less water evaporates.
Window Plant
Tap to learn moreFenestraria hides almost its whole body under the sand, out of the heat. Only the flat tips of its leaves show. Each tip has a clear window that lets sunlight shine down inside the leaf to the green cells below.
Century Plant
Tap to learn moreAn agave that may wait 40 years or more to flower. When it does, it drains the food from its leaves to shoot up a stalk many metres tall, a quarter of a metre a day. Hummingbirds visit the bright flowers at the top. Then the plant dies, leaving its seeds behind.
Living Stones
Tap to learn moreThese little African plants, Lithops, look exactly like pebbles. Each is just two fat leaves, marked to match the rocks around them, and plants growing on pale rocks are paler than those on reddish ones. A thirsty animal walks right past them.
Eyed Ladybird
Tap to learn moreBritain's largest ladybird, with pale rings round its spots. It hunts pine aphids, and it finds them by following the cloud of scent that pine trees give off when the aphids bite. The tree, in effect, calls for help.
Café Marron
Tap to learn moreA tree from Rodrigues in the Indian Ocean, once down to a single plant in the wild. When young its leaves are thin and dark, not green, so the island's giant tortoises, which had poor eyesight, didn't notice it; proper green leaves only grew once it was out of their reach.
Apply Your Knowledge
Each of these plants has its own answer to a hard life. Can you match them up?
Match the Plant to Its Survival Trick
Click an item to select it, then click the matching description to place it.
Real-World Challenge
There are about 400,000 kinds of plant on Earth, and many are disappearing faster than ever before. If you could choose ten plants to send to the Millennium Seed Bank first, how would you decide? Would you choose the rarest, the most useful to people, the ones animals depend on most, or something else? Explain your reasons.
Saving the World's Plants
David Attenborough says plants are disappearing faster than at any time in Earth's history. Here's how Kew and others are fighting back.
Response: By 1979 the café marron was thought to be extinct, until one plant was found on Rodrigues. Kew grew cuttings, but they never set seed. After months of experimenting with heat and light, Carlos Magdalena finally got them to produce seeds, so new young café marron plants could be grown at last.
Response: Kew's herbarium holds millions of dried specimens, a record of the world's plants through time, including some species known only from specimens because they're now extinct. Comparing a living plant with the original specimen proved the single café marron really was the lost tree.
Response: The Millennium Seed Bank, deep underground at Wakehurst in Sussex, is built to survive a bomb or a plane crash. Seeds collected with partners in many countries are dried and frozen there, so a species lost in the wild can one day be grown again and returned.
What Has Changed Since This Documentary Aired
This documentary was first shown in 2012. Here's what has changed since.
Updated: Many more. By the 2020s the seed bank and its partners had banked seeds from around 40,000 kinds of wild plant, well over two billion seeds, and it keeps growing every year.
Updated: No. In 2020 scientists in Israel reported growing six more date palms from ancient seeds found in archaeological sites near the Dead Sea, some of them around 2,000 years old. The first ancient palm, a male nicknamed Methuselah, has since pollinated one of the new female palms, and she has borne dates.
Updated: Botanists have found no good evidence that cistus sets itself alight. What is true is that cistus is built for fire: its seeds survive the heat in tough capsules and sprout readily afterwards, so a burnt hillside soon fills with young cistus.
Test Your Understanding
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Results
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Reflection
David Attenborough ends by saying plants are the very basis of all life on Earth. Think about everything you've eaten, worn and breathed today. How much of it can you trace back to a plant?
Sir David Attenborough showed us that Kew’s Millennium Seed Bank is safeguarding the future of global biodiversity by freezing seeds at minus twenty degrees centigrade. If you had to choose just one plant species to preserve in the vault for future generations, what would it be and why? Let us know your choices in the comments below!