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00:00Three trillion trees blanket our world.
00:12From spectacular cherries in spring,
00:17to the golden maples of North America,
00:22and the strange-looking baobab trees of Madagascar.
00:30They can bring us joy...
00:34..and even keep us alive.
00:38All these amazing trees around us give us the air that we breathe.
00:43But what do we really know about their hidden world?
00:47As you get closer to the tree, it just gets more and more remarkable.
00:52In this series, we'll follow their incredible lifespans.
00:56There are trees alive on Earth today that are as old as the Great Pyramids.
01:01Discover how trees communicate.
01:04This whole wood is interconnected,
01:08and that opens up so many possibilities.
01:11And learn how they survive in some of the toughest places on Earth.
01:15In this first episode, we're beginning with birth.
01:27And the journey to become an adult.
01:32As we reveal how trees mate.
01:35These flowers aren't for us.
01:39They're bold for trees to have sex.
01:42And even how a growing tree drinks.
01:46I can hear it.
01:48Oh, what a lovely sound.
01:51You'll never look at a tree in the same way again.
01:54There are more than 70,000 species of tree on our planet.
02:15But they all begin life in the same way.
02:25Even the giants of the tree world.
02:30The redwoods.
02:31The largest trees on Earth live in Northern California.
02:46Towering up to 116 metres, they're taller than the Statue of Liberty.
02:51Redwoods grow in Europe too.
03:06And some of the biggest are found at Benmore Botanic Garden
03:10in Western Scotland.
03:14Tony Kirken was the head of trees at Kew Gardens.
03:17He's spent a lifetime around the world's greatest trees.
03:24I spent 50 years of my professional career working with trees.
03:30And I'm still learning about them every day.
03:37So these trees are the giant redwoods.
03:40And they're my favourite trees.
03:42And I think it's probably because of the sheer size that they make.
03:45And how long they live for.
03:48Up to 3,000 years old.
03:50And they can have trunks about 8 metres diameter.
03:53So they, you know, they are monsters.
03:58These were planted in 1863.
04:01So they're just about 160 years old.
04:06They're taller than Nelson's Column.
04:08To put things into perspective.
04:1050, 55 metres.
04:11So they're tall.
04:14But like almost all trees, even these giants begin life as something tiny.
04:27Little seeds.
04:28So one of the incredible things about these massive trees is that they come from a seed this small.
04:37So tiny.
04:38Most people would think it would be the size of a coconut, you know, to make a tree this big.
04:42But they are minute.
04:43They are minute.
04:45To think that something so small can generate something so massive.
04:50All the redwoods and all the trees on the planet, three trillion of them, all grow from something so small.
04:58I think that's pretty amazing, astonishing actually.
05:08But how are seeds actually made in the first place?
05:12For many trees, the creation of new life begins with one of the most beautiful displays in the natural world.
05:27Blossom.
05:28Blossom.
05:29Blossom.
05:30Well, the rain is subtle.
05:32The rain is Hetalai Mountain.
05:33For a few brief weeks in Spring.
05:37Trees are painted in a fresh coat of colour.
05:41Blossom.
05:42As their flowers burst into life.
05:45Blossom.
05:48Heards Huic Lires.
05:49Blossom.
05:51From the vivid pinks of Japan's cherry trees.
05:54trees, to the pastel shades of almonds, apples, peaches and plums, and from
06:04magnolias, to the vibrant pomegranate tree.
06:14But as beautiful as it looks, all this colour isn't for us. It has a very
06:21important job, helping the tree to create new life in the form of seeds.
06:32This is one of my favourite times of the year, when all the colour starts to appear
06:37back into the countryside after such a long, barren, bleak winter.
06:43Biologist Connor Butler is visiting elder trees. Each elder has thousands of
06:51flowers, many more than most blossom trees. And in this orchard at Beaver Farm, the
07:00sweet-scented blooms are bursting into life. Connor is here to unlock the mystery
07:07of why many trees produce blossom. This field is filled with thousands and
07:13thousands of flowers and it smells really incredible right now. But these flowers
07:18aren't for us. They evolved for trees to have sex.
07:23Like us, to mate the next generation, trees need to reproduce.
07:32But when it comes to mating, they have a major problem. They are literally rooted to the spot.
07:39So unlike us, trees can't move. So in order for them to find a mate, they've actually got to find a pretty
07:45ingenious way to do that. And the way they've done that is to have flowers.
08:00The clever trees are using flowers to attract something that can move. Bees and other insects.
08:08To help them mate.
08:09So I've just caught this bee off this elderflower tree here. And this bee is visiting all of the
08:16flowers. And these flowers are really brightly coloured. They smell fantastic. And they contain
08:21a really sugary liquid called nectar. And the trees produce that nectar. They're trying to attract
08:27these pollinating insects in. The flowers look beautiful to us, but for insects, they look a whole
08:33other level of attractiveness.
08:38Trees use their bright flowers and sweet smelling nectar to lure in the bees. And whilst the bee is
08:46getting a tasty treat, the tree gives it something else to take away.
08:53Pollen.
08:55So pollen is essentially tree sperm. And it wants to get that pollen as far away as possible to a tree which
09:00could be hundreds and hundreds of meters away. And it uses bees and other insects to do that traveling.
09:08On beautiful spring days, as the air is filled with the scent of flowers,
09:15it also hums with the soundtrack of insects.
09:23A single bee can visit more than a thousand flowers in one day.
09:31Bees and trees working together to create a seed.
09:38So let's have a closer look at some of these flowers. What we can see here are the male parts,
09:43which are a bit kind of yellowish in colour. They're kind of sticking up out of the flower.
09:47And on each one of these is loads and loads of pollen grains. And when a bee or an insect visits the
09:52flower, it gets covered in this really dusty pollen. And when it's had its fill, it flies off to another
09:57flower. When it lands on that flower, it then deposits that pollen onto the female part, which is
10:03right in the centre of this flower. The pollen will make its way to an egg hidden inside.
10:11And that is the moment of conception. And that is where the seed starts to form.
10:23And actually, on some of these bunches here, we can see the petals have dropped off,
10:27and that will then swell and starts to grow into a seed.
10:34Most blossom only lasts a few short weeks in spring. Once the tree has shed its petals,
10:41it focuses its energy over the summer months, growing thousands of brand new seeds.
10:48But fewer than one in a thousand newly created seeds will make it into adulthood.
11:06So for many, there's a long and precarious journey ahead.
11:18It's summertime.
11:29And for trees, it's an important season for their precious offspring.
11:35The seeds are growing fast.
11:39And soon they'll be ready to leave home.
11:41To get the best start in life, they must take root far from the parent tree.
11:53And many have adopted ingenious ways to travel.
12:04Some use the wind,
12:05like the cleverly shaped helicopter seeds of sycamores and maples,
12:13catching a gust to be scattered far and wide.
12:20Other seeds are tucked away inside colorful fruits to entice hungry animals.
12:26They eat the fruit, but leave the seeds behind to take root away from the parent tree.
12:38And then, from the bare soil,
12:45a brand new tree begins to grow.
12:56But for many infant trees, the next stage of life can be challenging.
13:06In Italy, the steep slopes along its southern coastline are the perfect place to grow...
13:14lemon trees.
13:15Salvatore Aceto tends to 2,600 amalfi lemon trees on a 12-acre farm his family has worked for two centuries.
13:32I represent my sixth generation in the lemon farm, the business.
13:38The lemons are everything for us.
13:42We have a connection with the plants.
13:43We consider our plants like our relatives, part of our family.
13:47In our veins, we don't have blood, we have lemon juice.
13:57In Salvatore's orchard, he has a special nursery for the youngest infant trees.
14:07Lemon trees grow up fast.
14:10And by the age of just five,
14:12they're producing their own juicy fruit.
14:21It's huge.
14:26You can eat it like an apple.
14:28It is very sweet.
14:30You can't imagine.
14:31But there's a problem.
14:39Just like any infant, Salvatore's young trees can be reckless.
14:44These inexperienced youngsters are making more fruit than their slender branches can bear.
14:53We are having a lot of troubles on the young trees.
14:56The young trees get so carried away producing lemons, they're at risk of snapping their branches.
15:10So they're given a frame to hold onto as they grow.
15:14To support the lemons, we're tired and we use it like a scarf folding.
15:20Because it's the same as human nature.
15:21When you are young, you need more attention to the father, to the mother.
15:25It's the same for the plants.
15:26It's the same as a baby in the cradle.
15:34They stay nice, they have a support, and they can grow them better.
15:38Once they're matured, the trees can safely bear huge quantities of giant lemons.
15:49We have to wait 15, 20 years.
15:52This tree, like for example, this tree can give me 150 kilograms.
15:59Salvatore's tiny slice of the Amalfi Coast produces 70 tons of luscious lemons a year.
16:08And I know many people don't believe, but when I sell my lemons, I am jealous.
16:14I don't want to give up because I consider my lemons like a baby.
16:17I don't want to give my baby.
16:26After a long day in the orchard, Salvatore's wife Giovanna uses their precious fruit to make a meal for two.
16:38The lemons are everything for us.
16:44I eat, I drink lemons, I see lemons sometimes, I drink lemons.
16:51With this spaghetti, she cooks very well, it's simple.
16:54At the end of the day, what else?
16:56Spaghetti, the taste is very, very nice, a simple food.
17:01And the lemon zest, the lemon sauce, it's fantastic.
17:14From lemon trees growing in the Italian sunshine,
17:18to 11,000 trees thriving in one of the most famous gardens in the world.
17:33The Royal Botanic Gardens at Kew in London is home to 2,000 different species of tree.
17:40It's the perfect place to find out how young trees mature into adulthood.
17:55Just like us, all growing youngsters need to eat.
17:59And for a tree, its food is sunlight, which it gathers with its leaves.
18:11Cecily Withall is a member of Kew's tree gang.
18:16Her job is to keep a watchful eye on the health of the garden's trees.
18:21As a child, I climbed trees a lot.
18:31And my family now find it hilarious that I climb trees for a job as a grown-up.
18:35To get to literally work with these trees every day,
18:38it really is something that is beyond wonderful.
18:42The leaves at Kew span every conceivable shape, colour and size.
18:56Today, Cecily is checking up on some of her favourite trees.
19:02Starting with one that has some of the biggest leaves,
19:06the Indian bean tree, otherwise known as catalpa.
19:12So, as you can see, this is a huge leaf on the catalpa.
19:18And some can reach up to 30 centimetres in length,
19:21which is really big compared to other species of tree.
19:27Big leaves are ideal for taking on the most important job for any tree, feeding itself.
19:36The most amazing things that trees do is their ability to make their own food.
19:40So, we as humans have to source our food to fuel our bodies.
19:46But the tree here is making its own.
19:50Trees are very, very clever and they do something called photosynthesis.
19:54And that's when they're taking in the sun's energy through the sunlight that penetrates the leaf.
19:59When you look at that, it's a huge leaf. It's giving the most surface area to collect the light.
20:09Leaves combine the energy from the sun with water sucked up from the ground,
20:14as well as carbon dioxide from the air.
20:19A remarkable recipe that creates trees' food.
20:24I think it's pretty amazing that leaves are able to make and produce their own food,
20:28whereas we're still popping off to the shops.
20:31To catch as much nourishing sunlight as they can,
20:39trees spread their leaves over as great an area as possible.
20:47One single tree can grow two billion leaves.
20:52And all these leaves don't just feed the tree.
20:58By soaking up carbon dioxide from the air, trees also help to combat climate change.
21:09This purple-leaved oak has a vast leaf canopy.
21:14The thousands, hundreds of thousands of leaves covering this tree are doing such a huge job.
21:19It's spread out here as much as possible to make the most of that sunlight,
21:24and it's competing against all the trees around it as well.
21:28That's why you see canopies stretching out past other trees to really push them into the sunlight.
21:34They'll push their leaves and their branches out to find that source of the sun,
21:38because they obviously need it to survive.
21:40They'll push their leaves.
21:46Not far away is another of Q's gems.
21:50A tree with a distinctive leaf shape.
21:55The ginkgo.
22:00I think it's really hard not to create bonds with certain trees in the garden,
22:05and I think I've got a secret bond with the ginkgo, just because of its history and lineage.
22:14This tree was known to be growing 200 million years ago,
22:18and we still find fossils now that look identical to the leaf shape of the ginkgo.
22:23Ginkgos are one of the most ancient species of tree living on Earth.
22:35It's remarkable to think that leaves just like this were eaten by dinosaurs.
22:48But growing trees can't reach adulthood on sunlight alone.
22:53They need to drink vast amounts of water.
23:00But that begs the question.
23:02How do they survive in some of the hottest places on our planet?
23:24As a new day dawns,
23:28young trees stretch out their leaves towards the rising sun,
23:34gathering its energy as food.
23:38But growing trees can't live on sunlight alone.
23:41They must drink water.
23:50And finding enough to quench its thirst is a life-or-death challenge for a fragile young tree.
23:57But how does a tree survive if its home is a desert?
24:11Acacia trees grow in a part of Israel where it rains less than an inch in a whole year.
24:18And grow in places where they can tap into underground sources of water.
24:32Some as deep as 30 meters.
24:35Some as deep as many trees.
24:41In Madagascar, there's one of the planet's most unusual-looking trees.
24:48The otherworldly baobab.
24:50Known as the camels of the tree world, the wood inside their giant trunks acts like a sponge.
25:05Incredibly, each tree can suck up and hold 120,000 liters of water.
25:12That's as much as one of us would drink in a hundred years.
25:27In Australia, eucalyptus trees also manage to thrive in scorching heat.
25:34These young trees are some of the fastest growing on Earth.
25:38They need to drink a lot of water.
25:44So what does a tree do to quench its thirst?
25:51Wildlife sound recordist Ellie Williams is hoping to reveal exactly how they do it.
26:01When you look at a tree, it doesn't seem that similar to us.
26:05They seem still and passive and yet they share so many needs that we do.
26:11They need nutrients, they need to grow and they need to drink.
26:18Ellie believes that she can find out how a tree drinks simply by listening.
26:27This plantation is full of lots of different age eucalyptus trees.
26:32This one's really young and it's got really beautiful leaves with kind of pink veins and a pink rim.
26:38And the leaves are a really different shape as well in young eucalyptus trees and
26:42nobody really knows why.
26:44But there are some older trees
26:47in the other side so I'm going to wander over there now.
26:49This thirsty teenage tree is already 10 metres tall and should be ideal to listen to while it drinks.
27:11This is my contact mic and it does this magic thing of picking up the tiniest vibrations,
27:19or sound waves, through this metal pin.
27:25It's quite windy today.
27:40The first thing I notice is the kind of really warm rumblings and that's the big vibrations as the
27:45tree sways in the breeze.
27:46As she tunes in, Ellie taps into fainter sounds from within the tree.
28:03The breeze has slowed down a little bit, which might give me a chance to hear this really delicate
28:07sound, which is the sound I really want to hear.
28:10And if I'm lucky...
28:16Okay, that might have been one.
28:19Oh yeah, yeah, yeah, yeah, there was a little gurgle.
28:28I can hear it.
28:35Oh, what a lovely sound.
28:36It's like the most gentle little kind of series of bubbles.
28:47These faint popping noises are the sounds the young tree is making as it drinks,
28:55defying gravity as it sucks water all the way up its long trunk.
29:00So trees are full of these tiny little tubes. Imagine hundreds and hundreds of meters of tiny
29:09little drinking straws.
29:11And what the tree does is it pulls water and nutrients from the soil, through the roots,
29:18up through the trunk, into the branches, into the leaves.
29:21It's just these tiny little bubbling popping sounds.
29:28So that's basically the sound of air mixing with the water in the tubes.
29:34And eucalyptus trees are so, so thirsty. Each tree can drink about a bathtub's worth of water a day.
29:41You put these on and there's a whole other world going on and it's loud and it's dramatic and it's beautiful.
29:54So we kind of feel that trees aren't, aren't doing that much but they're doing so much.
29:57It makes you realise that there is all this life and movement happening all the time but we just don't notice it.
30:13The secret life of trees is happening all around us.
30:17Young trees that started life as tiny seeds are getting taller and stronger.
30:32But like most teenagers on their journey towards adulthood, the speed at which they grow is incredibly varied.
30:40Some trees gain height quickly.
30:48These weeping willows can grow by nearly three metres in a single year.
30:57They have far-reaching roots that draw on the abundance of water around them.
31:02Some of the slowest growing trees live high up in America's rocky mountains.
31:13This is the home of the whitebark pine.
31:20The trees spend eight months of the year shrouded in snow, leaving them just four months to grow.
31:27And to reach their adult size, it takes these pines an incredible 250 years, a quarter of a millennium.
31:45Every tree on earth is fed and nourished by gathering sunshine with their leaves and water from their roots.
31:53But how exactly do trees physically grow?
32:09In the new forest, Forestry England archaeologist Lawrence Shaw has an unusual way of finding out.
32:17When I'm walking through forests, I think it's probably a very different experience to most other people.
32:23As others might be listening out for birds or looking at the wildlife, I'm interpreting how people have interacted with this landscape over millennia.
32:36Lawrence is looking for tree graffiti.
32:41The carvings that people have made on trees in the past.
32:44Isn't this tree just beautiful and it's absolutely littered with historic tree graffiti, people leaving their mark.
32:54They can date back hundreds, sometimes thousands of years and they can connect us to individuals, specific events, a whole host of different things.
33:04So we have two initials here and a beautifully signed signature of TB James and the year of 1944, all carved into the tree bark of this beech tree.
33:15And we know that American service personnel were stationed here in advance of the D-Day landing and there's every probability that TB James was an American serviceman who was part of that assault on Normandy on that fateful night that was going to shape the war and the world for years to come.
33:35These days we shouldn't carve our names into trees as it can harm them.
33:44But these inscriptions from history can help Lawrence uncover the secret of how this beech tree has grown.
33:55Whilst the tree is several meters taller than it was during the Second World War, the carving itself hasn't moved any higher.
34:03It's been, yeah, 80 years since, but what's lovely to see is that it's still at exactly the same height that that individual carved those.
34:13So whilst the tree has grown upwards, this has stayed where it is.
34:24This tells us that the tree has gained all its new height at the top of its trunk, rather than growing upwards from its base.
34:33Now Lawrence is in search of older tree graffiti to see if the same is true even after hundreds of years have passed.
34:47So the new forest was created by William the Conqueror in 1079 as a royal hunting forest.
34:54Over the next seven centuries, thousands of trees were planted for England's kings and queens.
35:10Oaks provided wood for the warships of Henry VIII and Elizabeth I.
35:15And Lawrence knows of a special tree still standing that was growing in the 1800s when George III's navy was fighting sea battles against Napoleon Bonaparte.
35:31So this is a lovely example of a king's mark on this beech tree.
35:41So you've got the shaft with the arrow coming down the trunk of the tree with the two returns making the point of the arrow there.
35:48And this is used to mark and infantry trees that are going to be used for shipbuilding.
35:52The arrow told foresters not to cut it down.
35:59The wood was to be saved for a warship.
36:03The mark on this beech tree was made around 200 years ago.
36:07At the time, the tree was still young and only a few metres tall.
36:16Over the past two centuries, the tree has added at least 20 metres in height and yet the mark hasn't moved at all.
36:25I'm basically stood at the same head level as the individual that drew this carving.
36:31200 years ago, this tree would have been thinner,
36:34but the mark itself is at the same position that it was drawn at that time.
36:40What's lovely about historic tree graffiti is that they demonstrate the growing processes of trees.
36:45It may warp as a tree grows wider.
36:51But certainly these things don't disappear up with the tree.
36:56The 200-year-old carving proves that trees don't grow from the base of their trunk.
37:04Instead, as they get taller, all the tree's growth happens higher up,
37:11as it stretches its branches towards the sunlight.
37:19If trees do most of their growing throughout the warm summer months,
37:23the tree's growths, how do they prepare themselves for the freezing weather of winter?
37:30It's autumn, a spectacular time in a tree's calendar.
37:49After gathering in the sunlight of summer,
37:55many trees must do one last remarkable thing before they can rest over winter.
38:01This is Forestry England's Western Burt Arboretum in Gloucestershire.
38:18Arborist Joe Porter looks after its 15,000 trees.
38:23He's fascinated by why, in autumn, many erupt into a riot of colour.
38:36As you can see, the trees are putting on some lovely colour for us.
38:43It's great to see so many people enjoying
38:47all of these beautiful trees and enjoying having that connection with nature.
38:51With the busyness of our job, every now and then it is quite nice just to stop,
38:56take a look and see this colour and it sort of lifts your spirits a little bit.
39:01But it's also not just for us that they're doing this.
39:03There's also a lot of important stuff going on inside the trees as they prepare for winter.
39:14Many of the two and a half thousand species of trees here are deciduous,
39:21which means they lose their leaves every year after a flourish of autumn colour.
39:27And none are more dramatic than the acers.
39:37Acer is the botanical name for a maple tree.
39:41You tend to see a lot of these plants in people's gardens.
39:44The leaf shape looks like your hand. It helps them with wind deflection.
39:50The wind can move through the leaves and it causes less damage when it does get up to high winds.
39:57They're a little bit of a marker for when autumn has come.
40:00They go in this beautiful colour and they brighten up people's gardens
40:03when gloomy weather comes and they're just this brilliant sort of show at the beginning of autumn.
40:09But why do leaves change their colour from green to vibrant shades of red and gold?
40:18So this time of year, as autumn moves through and we move into winter,
40:22the trees have got to prepare themselves for shorter days and colder temperatures.
40:27Leaves could get damaged in winter with frostbite, high winds.
40:31So they've got to prepare themselves and get themselves ready for this hibernation time of year for them.
40:42Over the summer, the leaves have been gathering energy from sunshine.
40:47In autumn, the colour changes we see from greens to oranges, yellows and reds
40:58are caused by the trees stopping this food making process.
41:02When we see green leaves like this, it's because they're full of what we call chlorophyll.
41:11It's a chemical inside the leaf that helps the tree to photosynthesise and create food for itself.
41:22What we see throughout the process of autumn is the breakdown of that chlorophyll,
41:26as it draws all of its good nutrients back into itself.
41:32Trees sense the shorter days and cooler air of autumn.
41:37It triggers them to claw back their harder nutrients, removing the green and revealing the naked leaf beneath.
41:45And what we are seeing is this natural hue in behind, which is the colour that is present all year round,
41:54but you just don't see it because the chlorophyll is so dominating in its colour.
41:57As the trees slowly break down the chlorophyll, different combinations of chemicals are left behind.
42:10They've had this gradual transition throughout autumn,
42:14trying to get that every last bit of sunlight that they can before winter comes along.
42:27So here we have one of our younger acers. You can tell it's a really good and healthy and vigorous tree.
42:41Quite often when you see trees dropping their leaves, it can be seen as quite a sad thing.
42:45But it's a really positive move for the tree as it hunkers down for the winter, protects itself,
42:51and then there's some tiny little buds starting to poke through,
42:55which means it's ready come springtime to sort of burst forth and continue producing its food from its leaves.
43:10And in a few days or weeks, this spectacle will be over.
43:18As trees let the wind carry away the leaves they no longer need.
43:25For every deciduous tree, it's a vital stage in their long lives.
43:36As they fall into a winter slumber,
43:40they've ensured that they have saved enough energy to get taller and stronger for next spring
43:48and the year ahead.
43:55Next time, we follow trees in the prime of their lives as they do the most extraordinary things.
44:03These trees here, they are essentially talking to each other.
44:08Adapting to withstand attacks from nature.
44:10As they grow into the largest living things on the planet's surface.
44:23As they grow into the largest living things on the planet's surface.
44:25It blows my mind and even though I've been working with trees for 50 years,
44:30it still fascinates me how they stand up.
44:32For more information about the secret life of British trees,
44:37trees, go to the Woodland Trust at woodlandtrust.org.uk
44:43The Secret Life of Trees continues brand new next Friday at nine.
44:53From North Korea to Nigeria, follow Michael Palin's adventures around the world,
44:58streaming now on five.
45:00And what makes Princess Anne a quite remarkable royal?
45:03We explore her extraordinary career brand new tomorrow at nine.
45:07Next, lip reading the royals, The Secret Conversations.
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