The Secret Life of Trees (2025) s01e01 Episode Script

MICHAEL PALIN: Three trillion trees
blanket our world
..from spectacular cherries
in spring
..to the golden maples
of North America
..and the strange-looking
baobab trees of Madagascar.
They can bring us joy
..and even keep us alive.
All these amazing trees around us
give us the air that we breathe.
But what do we really know
about their hidden world?
As you get closer to the tree, it
just gets more and more remarkable.
In this series, we'll follow
their incredible life spans
There are trees alive on earth today
that are as old
as the Great Pyramids.
..discover how trees communicate
This whole wood is interconnected,
and that opens up
so many possibilities.
..and learn how they survive in some
of the toughest places on earth.
In this first episode,
we're beginning with birth
..and the journey
to become an adult
..as we reveal how trees mate
These flowers aren't for us.
They evolved for trees to have sex.
..and even how
a growing tree drinks.
You can hear it.
GENTLE BUBBLING
Oh, what a lovely sound.
You'll never look at a tree
in the same way again.
There are more than 70,000
species of tree on our planet.
But they all begin life
in the same way
..even the giants
of the tree world
..the redwoods.
The largest trees on earth
live in Northern California.
Towering up to 116 metres, they're
taller than the Statue of Liberty.
Redwoods grow in Europe, too.
And some of the biggest
are found at Benmore Botanic Garden
in Western Scotland.
Tony Kirkham was the head of trees
at Kew Gardens.
He's spent a lifetime
around the world's greatest trees.
I spent 50 years in my professional
career working with trees,
and I'm still learning about them
every day.
So, these trees
are the giant redwoods,
and they're my favourite trees.
And I think it's probably cos
of their sheer size that they make
and how long they live for,
up to 3,000 years old.
And they can have trunks
about eight metres diameter.
So, you know, they are monsters.
These were planted in 1863,
so they're just about 160 years old.
They're taller than Nelson's Column,
to put things into perspective.
50, 55 metres. So they're tall.
But like almost all trees,
even these giants begin life
as something tiny
..little seeds.
So, one of the incredible things
about these massive trees
is that they come
from a seed this small.
So tiny.
Most people would think
it'd be the size of a coconut,
you know, to make a tree this big,
but they are minute.
To think that something so small
can generate something so massive.
All the redwoods
and all the trees on the planet -
three trillion of them -
all grow from something so small.
I think that's pretty amazing -
astonishing, actually.
But how are seeds actually made
in the first place?
For many trees,
the creation of new life begins
with one of the most beautiful
displays in the natural world
..blossom.
For a few brief weeks in spring,
trees are painted
in a fresh coat of colour
..as their flowers burst into life.
From the vivid pinks
of Japan's cherry trees
..to the pastel shades of almonds,
apples, peaches and plums.
And from magnolias
..to the vibrant pomegranate tree.
But as beautiful as it looks,
all this colour isn't for us.
It has a very important job -
helping the tree to create new life
in the form of seeds.
CONNOR BUTLER: This is one
of my favourite times of the year,
when all the colour starts to appear
back into the countryside
after such a long, barren,
bleak winter.
Biologist Connor Butler
is visiting elder trees.
Each elder has thousands of flowers,
many more than most blossom trees.
And in this orchard at Beaver Farm,
the sweet-scented blooms
are bursting into life.
Connor is here to unlock the mystery
of why many trees produce blossom.
So, this field is filled with
thousands and thousands of flowers,
and it smells really incredible
right now.
But these flowers aren't for us.
They evolved for trees to have sex.
Like us, to make the next
generation, trees need to reproduce.
But when it comes to mating,
they have a major problem
..they are literally rooted
to the spot.
So, unlike us, trees can't move,
so in order for them to find a mate,
they've actually got to find
a pretty ingenious way to do that.
And the way they've done that
is to have flowers.
The clever trees are using flowers
to attract something that can move -
bees and other insects -
to help them mate.
So, I've just caught this bee
off this elderflower tree here.
And this bee
is visiting all the flowers.
And these flowers
are really brightly coloured,
they smell fantastic,
and they contain a really
sugary liquid called nectar.
And the trees produce that nectar
to try and attract
these pollenating insects in.
The flowers look beautiful to us,
but for insects, they look a whole
other level of attractiveness.
Trees use their bright flowers
and sweet smelling nectar
to lure in the bees.
And whilst the bee
is getting a tasty treat,
the tree gives it
something else to take away
..pollen.
So, pollen is essentially
tree sperm,
and it wants to get that pollen
as far away as possible
to a tree which could be hundreds
and hundreds of metres away.
And it uses bees and other
insects to do that travelling.
On beautiful spring days
..as the air is filled
with the scent of flowers
..it also hums
with a soundtrack of insects.
BUZZING
A single bee can visit more than
a thousand flowers in one day
..bees and trees working together
to create a seed.
So, let's have a closer look
at some of these flowers.
What we can see here
are the male parts,
which are the bits that are
kind of yellowish in colour,
they're kind of sticking up
out of the flower.
And on each one of these
is loads and loads of pollen grains.
And when a bee or an insect
visits the flower,
it gets covered
in this really dusty pollen.
And when it's had its fill,
it flies off to another flower.
When it lands on that flower,
it then deposits that pollen
onto the female part,
which is right in this centre
of this flower.
The pollen will make its way
to an egg hidden inside.
And that
is the moment of conception.
And that is
where the seed starts to form.
And actually,
on some of these bunches here,
we can see
the petals have dropped off,
and that will then swell,
and it starts to grow into a seed.
Most blossom only lasts
a few short weeks in spring.
Once the tree has shed its petals,
it focuses its energy
over the summer months
growing thousands
of brand-new seeds.
But fewer than one in a thousand
newly created seeds
will make it into adulthood.
So for many, there's a long
and precarious journey ahead.
It's summertime.
And for trees, it's an important
season for their precious offspring.
The seeds are growing fast
..and soon,
they'll be ready to leave home.
To get the best start in life,
they must take root
far from the parent tree.
And many have adopted
ingenious ways to travel.
Some use the wind
..like the cleverly shaped
helicopter seeds
of sycamores and maples
..catching a gust
to be scattered far and wide.
Other seeds are tucked away
inside colourful fruits,
to entice hungry animals.
They eat the fruit
but leave the seeds behind
to take root
away from the parent tree.
And then, from the bare soil
..a brand new tree begins to grow.
But for many infant trees, the next
stage of life can be challenging.
In Italy, the steep slopes
along its southern coastline
are the perfect place to grow
..lemon trees.
Salvatore Aceto
tends to 2,600 Amalfi lemon trees
on a 12-acre farm his family
has worked for two centuries.
I represent my sixth generation
in the lemon farm, the business.
The lemons are everything for us.
We have a connection
with the plants.
We consider our plants like
our relatives, part of our family.
In our veins, we don't have blood,
we have lemon juice.
In Salvatore's orchard,
he has a special nursery
for the youngest infant trees.
Lemon trees grow up fast
..and by the age of just five,
they're producing
their own juicy fruit.
Mm? It's huge!
You can eat like an apple.
This is very sweet.
You can't imagine.
But there's a problem.
Just like any infant, Salvatore's
young trees can be reckless.
These inexperienced youngsters
are making more fruit than
their slender branches can bear.
We are having a lot of troubles
on the young trees,
because when the plant
has too much lemons,
can be a little bit dangerous.
The young trees get so carried away
producing lemons,
they're at risk
of snapping their branches,
so they're given a frame
to hold onto as they grow.
To support the lemons, we tie it,
and we use as like a scaffolding.
Because it's the same
in human nature -
when you are young,
you need more attention
through the father, the mother.
It's the same for the plants.
It's the same a baby in the cradle.
They stay nice, they have support
and they can grow better.
Once they're matured,
the trees can safely bear
huge quantities of giant lemons.
We have to wait 15, 20 years.
This tree, like, for example,
this tree can give me 150 kilograms.
Salvatore's tiny slice
of the Amalfi coast
produces 70 tonnes
of luscious lemons a year.
And I know
many people don't believe,
but when I sell my lemons,
I am jealous.
I don't wanna give 'em, because
I consider my lemons like a baby.
CHUCKLING:
I don't wanna give my baby.
After a long day in the orchard,
Salvatore's wife, Giovanna,
uses their precious fruit
to make a meal for two.
The lemons are everything for us.
I eat, I drink lemons, I see lemons.
Sometimes I dream lemons.
HE LAUGHS
With this spaghetti,
she cooks very well, simple.
At the end of the day, what else?
Spaghetti.
The taste is very, very nice.
Simple food.
And the lemon zest, the lemon sauce,
it's fantastic.
From lemon trees
growing in the Italian sunshine
..to 11,000 trees
thriving in one of the most
famous gardens in the world.
The Royal Botanic Gardens
at Kew in London
is home to 2,000 different species
of tree.
It's the perfect place
to find out how young trees
mature into adulthood.
Just like us,
all growing youngsters need to eat.
And for a tree,
its food is sunlight
..which it gathers with its leaves.
Cecily Whithall
is a member of Kew's tree gang.
Her job is to keep a watchful eye
on the health of the garden's trees.
As a child, I climbed trees a lot,
and my family now find it hilarious
that I climb trees
for a job as a grown up.
To get to literally work
with these trees every day,
it really is something
that is beyond wonderful.
The leaves at Kew span every
conceivable shape, colour and size.
Today, Cecily's checking up
on some of her favourite trees
..starting with one that has
some of the biggest leaves
..the Indian bean tree
..otherwise known as catalpa.
So, as you can see,
this is a huge leaf on the catalpa,
and some can reach
up to 30 centimetres in length,
which is really big
compared to other species of tree.
Big leaves are ideal
for taking on the most important job
for any tree -
feeding itself.
The most amazing things
that trees do
is their ability
to make their own food.
So, we as humans have to source
our food to fuel our bodies.
But the tree here is making its own.
Trees are very, very clever,
and they do something
called photosynthesis,
and that's when they're taking in
the sun's energy
through the sunlight
that penetrates the leaf.
When you look at that,
it's a huge leaf.
It's giving the most surface area
to collect the light.
Leaves combine
the energy from the sun
with water
sucked up from the ground,
as well as carbon dioxide
from the air -
a remarkable recipe
that creates trees' food.
I think it's pretty amazing
that leaves are able
to make and produce their own food,
whereas we're still
popping off to the shops.
To catch as much nourishing sunlight
as they can,
trees spread their leaves
over as great an area as possible.
One single tree can grow
two billion leaves.
And all these leaves
don't just feed the tree.
By soaking up carbon dioxide
from the air,
trees also help
to combat climate change.
This purple-leafed oak
has a vast leaf canopy.
The thousands, hundreds of thousands
of leaves covering this tree
are doing such a huge job.
They spread out here
as much as possible
to make the most of that sunlight,
and it's competing against
all the trees around it as well.
That's why you see canopies
stretching out past other trees
to really push them
into the sunlight.
They'll push their leaves
and their branches out
to find that source of the sun
because they obviously need it
to survive.
Not far away
is another of Kew's gems
..a tree
with a distinctive leaf shape
..the gingko.
I think it's really hard
not to create bonds
with certain trees in the garden.
And I think I've got
a secret bond with the gingko
just because
of its history and lineage.
This tree was known to be growing
200 million years ago,
and we still find fossils now
that look identical
to the leaf shape of the gingko.
Gingkoes are one of the most ancient
species of tree living on Earth.
It's remarkable to think
that leaves just like this
were eaten by dinosaurs.
But growing trees can't reach
adulthood on sunlight alone.
They need to drink
vast amounts of water.
But that begs the question -
how do they survive in some
of the hottest places on our planet?
MICHAEL PALIN: As a new day dawns
..young trees stretch out their
leaves towards the rising sun
..gathering its energy as food.
But growing trees can't live
on sunlight alone.
They must drink water.
And finding enough
to quench its thirst
is a life-or-death challenge
for a fragile young tree.
But how does a tree survive
if its home is a desert?
Acacia trees grow
in a part of Israel
where it rains less than an inch
in a whole year.
To thrive,
these trees have extra-long roots
and grow in places
where they can tap into
underground sources of water
..some as deep as 30 metres.
In Madagascar,
there's one of the planet's
most unusual-looking trees
..the otherworldly baobab.
Known as the camels
of the tree world,
the wood inside their giant trunks
acts like a sponge.
Incredibly,
each tree can suck up and hold
120,000 litres of water.
That's as much as one of us
would drink in a hundred years.
In Australia, eucalyptus trees also
manage to thrive in scorching heat.
These young trees are some
of the fastest growing on Earth.
They need to drink a lot of water.
So what does a tree do
to quench its thirst?
Wildlife sound recordist
Ellie Williams
is hoping to reveal
exactly how they do it.
ELLIE: 'When you look at a tree,
it doesn't seem that similar to us.
'They seem still and passive.'
And yet they share
so many needs that we do.
They need nutrients.
They need to grow,
and they need to drink.
Ellie believes that she can find out
how a tree drinks
simply by listening.
This plantation is full of lots
of different-age eucalyptus trees.
This one's really young,
and it's got really beautiful leaves
with kind of pink veins
and a pink rim.
And the leaves are
a really different shape as well
in young eucalyptus trees,
and nobody really knows why.
But there are some older trees
on the other side,
so I'm gonna wander over there now.
This thirsty teenage tree
is already ten metres tall
and should be ideal to listen to
while it drinks.
This is my contact mic.
And it does this magic thing
of picking up the tiniest vibrations
or soundwaves
through this metal pin.
RUMBLING,
CREAKING
It's quite windy today.
The first thing I notice is
the kind of really warm rumblings,
and that's the big vibrations
as the tree sways in the breeze.
As she tunes in, Ellie taps into
fainter sounds from within the tree.
FAINT RUMBLING,
CREAKING
The breeze has slowed down
a little bit,
which might give me a chance
to hear this really delicate sound,
which is the sound
I really want to hear.
And if I'm lucky
FAINT CREAKING,
GURGLING
OK. That might have been one.
POPPING,
SHE INHALES SHARPLY
Oh, yeah. Yeah, yeah, yeah.
There was a little gurgle.
FAINT RUMBLING,
POPPING
I can hear it.
POPPING INTENSIFIES
Oh, what a lovely sound.
It's like the most gentle,
little kind of
series of bubbles.
These faint popping noises
are the sounds the young tree
is making as it drinks
..defying gravity as it sucks water
all the way up its long trunk.
So, trees are full
of these tiny little tubes.
Imagine hundreds
and hundreds of metres
of tiny little drinking straws.
And what the tree does is it pulls
water and nutrients from the soil,
through the roots,
up through the trunk,
into the branches,
into the leaves.
It's just these tiny, little
bubbling, popping sounds.
POPPING,
RUMBLING
So that's basically the sound of air
mixing with the water in the tubes.
And eucalyptus trees
are so, so thirsty.
Each tree can drink about
a bathtub's worth of water a day.
You put these on, and there is
a whole other world going on,
and it's loud, and it's dramatic,
and it's beautiful.
RUMBLING,
POPPING
So, we kind of feel like
trees aren't doing that much,
but they're doing so much.
It makes you realise
that there is all this life
and movement happening all the time,
but we just don't notice it.
The secret life of trees
is happening all around us.
Young trees that started life
as tiny seeds
are getting taller and stronger.
But like most teenagers
on their journey towards adulthood,
the speed at which they grow
is incredibly varied.
Some trees gain height quickly.
These weeping willows can grow
by nearly three metres
in a single year.
They have far-reaching roots
that draw on the abundance of water
around them.
Some of the slowest-growing trees
live high up
in America's Rocky Mountains.
This is the home
of the whitebark pine.
The trees spend eight months
of the year shrouded in snow,
leaving them
just four months to grow.
And to reach their adult size,
it takes these pines
an incredible 250 years -
a quarter of a millennium.
Every tree on Earth
is fed and nourished
by gathering sunshine
with their leaves
and water from their roots.
But how exactly
do trees physically grow?
In the New Forest,
Forestry England archaeologist
Lawrence Shaw
has an unusual way of finding out.
LAWRENCE:
'When I'm walking through forests,
'I think it's probably
a very different experience
'to most other people.'
As others might be listening out for
birds or looking at the wildlife,
I'm interpreting
how people have interacted
with this landscape over millennia.
Lawrence is looking
for tree graffiti
..the carvings that people have made
on trees in the past.
Isn't this tree just beautiful?
And it's absolutely littered
with historic tree graffiti,
people leaving their mark.
They can date back hundreds,
sometimes thousands of years,
and they can connect us
to individuals, specific events,
a whole host of different things.
So, 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.
And 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 gonna shape the war
and the world for years to come.
These days, we shouldn't carve
our names into trees,
as it can harm them.
But these inscriptions from history
can help Lawrence uncover the secret
of how this beech tree has grown.
Whilst the tree
is several metres taller
than it was
during the Second World War,
the carving itself
hasn't moved any higher.
It'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.
So whilst the tree
has grown upwards,
this has stayed where it is.
This tells us that the tree
has gained all its new height
at the top of its trunk,
rather than growing upwards
from its base.
Now Lawrence is in search
of older tree graffiti
to see if the same is true,
even after hundreds of years
have passed.
So, the New Forest was created
by William the Conqueror
in 1079 as a royal hunting forest.
Over the next seven centuries,
thousands of trees were planted
for England's kings and queens.
Oaks provided wood for the warships
of Henry VIII and Elizabeth I.
And 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.
So, this is a lovely example
of a king's mark on this beech tree.
So, you've got the shaft
of the arrow
coming down the trunk of the tree,
with the two returns
making the point of the arrow there.
And this is used to mark
and inventory trees
that are gonna be used
for shipbuilding.
The arrow told foresters
not to cut it down.
The wood was to be saved
for a warship.
The mark on this beech tree
was made around 200 years ago.
At the time,
the tree was still young
and only a few metres tall.
Over the past two centuries,
the tree has added
at least 20 metres in height,
and yet the mark
hasn't moved at all.
I'm basically stood
at the same head level
as the individual
that drew this carving.
200 years ago,
this tree would have been thinner,
but the mark itself
is at the same position
that it was drawn at that time.
What's lovely
about historic tree graffiti
is that they demonstrate
the growing processes of trees.
It may warp as the tree grows wider.
But, certainly, these things
don't disappear up with the tree.
The 200-year-old carving
proves that trees don't grow
from the base of their trunk.
Instead, as they get taller,
all the tree's growth
happens higher up
..as it stretches its branches
towards the sunlight.
If trees do most of their growing
throughout the warm summer months
..how do they prepare themselves
for the freezing weather of winter?
MICHAEL PALIN: It's autumn,
a spectacular time
in a tree's calendar.
After gathering
the sunlight of summer,
many trees must do
one last remarkable thing
before they can rest over winter.
This is Forestry England's
Westonbirt arboretum
in Gloucestershire.
Arborist Joe Porter looks after
its 15,000 trees.
He's fascinated by why, in autumn,
many erupt into a riot of colour.
As you can see,
the trees are putting on
some lovely colour for us.
It's great to see
so many people enjoying
all of these beautiful trees
and enjoying having
that connection with nature.
With the busyness of our job,
every now and then,
it is quite nice just to stop,
take a look and see this colour,
and it sort of lifts your spirits
a little bit.
But it's also not just for us
that they're doing this.
There's also a lot
of important stuff going on
inside the trees
as they prepare for winter.
Many of the 2,500 species
of trees here are deciduous
..which means they lose their leaves
every year
..after a flourish of autumn colour.
And none are more dramatic
than the acers.
So, acer is the botanical name
for a maple tree.
You tend to see a lot of these
planted in people's gardens.
The leaf shape looks like your hand.
It helps them with wind deflection.
The wind can move
through the leaves,
and it causes less damage
when it does get up to high winds.
They're a little bit of a marker
for when autumn has come.
They go this beautiful colour,
and they brighten up
people's gardens
when the gloomy weather comes,
and they're this brilliant show
at the beginning of autumn.
But why do leaves change
their colour from green
to vibrant shades of red and gold?
So, this time of year,
as autumn moves through
and we move into winter,
the trees have got
to prepare themselves
for shorter days
and colder temperatures.
Leaves could get damaged in winter
with frostbite, high winds.
So they've gotta prepare themselves
and get themselves ready
for this hibernation
time of year for them.
Over the summer,
the leaves have been gathering
energy from sunshine.
In autumn,
the colour changes we see,
from greens to oranges,
yellows and reds
..are caused by the trees stopping
this food-making process.
When we see green leaves like this,
it's because they're full
of what we call chlorophyll.
It's a chemical inside the leaf
that helps the tree
to photosynthesise
and create food for itself.
What we see
throughout the process of autumn
is the breakdown
of that chlorophyll
as it draws all of
its good nutrients back into itself.
Trees sense the shorter days
and cooler air of autumn.
It triggers them to claw back
their hard-earned nutrients,
removing the green and revealing
the naked leaf beneath.
And what we are seeing
is its natural hue in behind,
which is the colour
that is present all year round
but you just don't see it,
because the chlorophyll
is so dominating in its colour.
As the trees slowly break down
the chlorophyll,
different combinations of chemicals
are left behind.
They've had this gradual transition
throughout autumn,
trying to get that every last bit
of sunlight that they can
before winter comes along.
So, here we have
one of our younger acers.
You can tell it's a really good
and healthy and vigorous tree.
Quite often when you see
trees dropping their leaves,
it can be sort of seen
as quite a sad thing.
But it's a really positive move
for the tree
as it hunkers down for the winter,
protects itself.
And then there's some tiny little
buds starting to poke through,
which means it's ready,
come springtime,
to sort of burst forth
and, yeah, continue producing
its food from its leaves.
And in a few days or weeks,
this spectacle will be over
..as trees let the wind carry away
the leaves they no longer need.
For every deciduous tree,
it's a vital stage
in their long lives.
As they fall
into a winter slumber
..they've ensured that they have
saved enough energy
to get taller and stronger
for next spring
..and the year ahead.
Next time,
we follow trees
in the prime of their lives
as they do
the most extraordinary things
These trees here, they are
essentially talking to each other.
..adapting to withstand
attacks from nature
..and from us
You had chimneys belching out
smoke, soot,
and this tree managed
to deal with that.
..as they grow
into the largest living things
on the planet's surface.
It blows my mind,
and even though I've been working
with trees for 50 years,
it still fascinates me
how they stand up.
For more information about
the secret life of British trees,
go to the Woodland Trust at