The Secret Life of Trees (2025) s01e03 Episode Script

3 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.
So far, we've learnt
how even the mightiest trees
begin life as tiny seeds.
And we followed them as they thrived
through their mid-life years.
In this final episode,
we'll meet the surprisingly spritely
elder statesman of the tree world.
As trees get old,
they get really exciting.
When the old tree's had enough,
that newly-rooted branch
can start to grow.
And we'll join them
through the final stage
of their remarkable journey.
When a tree dies,
you get to see its past life.
It may look dead
but actually, it's doing far more
than the eye can see.
You'll never look at a tree
in the same way again.
Trees are extraordinary
for so many reasons.
But possibly, the most amazing to us
is their incredibly long life span.
They say it takes an oak tree
300 years to grow.
300 years to live.
And 300 years to die.
But this third chapter
in a tree's long life
is full of surprises.
Especially when some of
the oldest trees on the planet
can live for nearly 5,000 years.
But how do you tell the age
of a tree?
Professor Mary Gagen
from Swansea University
investigates the life stories
of ancient trees.
Trees are just
absolutely wonderful things.
They're some of the biggest,
most majestic natural things
that we see in our environment.
And they also grow with us.
A tree that's small
when we're small,
will be a big, tall,
majestic veteran as we age.
And that way that trees grow
is really important
because it means
that we can find out things
about that tree's life history
from looking inside them.
So, we've got this lovely,
healthy sycamore.
They're a really common tree
in our woodland.
And looking at it,
we can tell a few things about it,
its health, its history,
but if I want to know more
about what it's experienced,
I need to look
inside the tree trunk.
And we use this to take a small core
from inside.
So, a little bit of hard work
to get the core sample out.
For a tree this large,
having a core taken is just like us
getting a blood test.
The tree will soon seal over
the small hole.
I'm gonna pop this in
to slide underneath the core.
Nice. A lovely core there.
And it's just really small.
So what I can see
is what look like stripes
inside this little piece of wood.
And they are the growth rings.
Trees don't grow in a haphazard way.
They grow one ring every year.
And time is marked through this core
in these series
of light and dark bands.
The faster growth of spring
makes a lighter-coloured band.
Slower growth, in late summer
and autumn, makes a darker band.
365 days
of the tree gathering sunshine,
making its food,
and growing bigger and stronger
..all compressed and recorded
in light and dark rings.
Counting the number of these rings
tells us the exact age of a tree.
So that history is hidden
inside its trunk -
everything that has gone on
in its long life.
But tree rings
don't just mark the passage of time,
they can also reveal
something remarkable,
a tree's memories.
Because not every ring
is the same size.
Where you see a wide ring,
something good has happened
to this tree in that year.
Maybe it was very sunny,
there was lots of water,
and the tree was able to grow
a lovely, wide tree ring.
And that history
of what's gone on in the woodland
is almost like a diary
that the tree records
as it grows through time.
And we can have a look at that diary
and read it.
Incredibly,
tree rings can offer glimpses
into specific events in our history.
And reveal how the tree reacted
to them.
This is a piece of oak
from the southeast of the UK,
and this tree died in 1982.
And the outside rings
are nice and wide.
We can see 1982, '81, 1980, '79,
1978, '77.
And then we reach, in 1976,
there is suddenly
an incredibly narrow ring.
In 1976, the UK was hit
by the worst drought for 250 years.
For the nation's trees,
it was a battle for survival
as they competed for the scarce
water that remained underground.
It was an incredibly dry spring
and summer,
and thousands of trees
didn't survive that drought.
But this tree is a real survivor,
it managed to hang on,
even though it could only grow
a really narrow ring.
This traumatic drought left its scar
in the form of the narrow ring.
But what's really interesting
is what the tree did next.
Its neighbours probably
didn't do so well and died
because in the years after 1976,
this tree grows really wide rings
to take advantage of that space
as it recovers from that drought.
After the drought,
this stump's remarkable diary
has recorded how the tree
responded to it,
with six years of healthy growth.
So, do trees have memory?
In some sense, the rings inside
their trunks are their memory.
Trees are all individuals,
and this one was able to recover
quickly and grow wide rings.
But not all trees do that.
Sometimes, those traumatic events
stay in the tree's memory
for decades and decades,
and you see the memory
of that recovery
in years and years of slower growth
and narrower growth
as the tree gives itself time
to get over that event.
Scientists are only
just beginning to understand
how long tree memories can last.
And even if these lessons in life
could be passed on
to the next generation.
One of the most useful things about
looking at how a tree like this
has responded to a drought
in the past
is that it gives us clues
about how trees might respond
to droughts and to extreme events
in the future
as our climate changes.
So, if trees could learn
from events in their past,
what other secrets do they keep
for an incredibly long life?
And which trees have survived
to become the oldest living things
on Earth?
This is Traquair House
..Scotland's oldest
continually-inhabited home.
It's hosted passing kings and queens
for over 900 years.
And in its grounds
are Europe's longest-living trees.
Yews.
Yew trees can grow up
to 20 metres tall
and their canopies
of evergreen needle-like leaves
can spread across 300 square metres.
Expert Tony Kirkham
has come to uncover the tricks these
trees use to reach a ripe old age.
I know I have many favourite trees
but this is one of my favourites.
And many people think it's quite
a boring tree, because it's green,
you know,
it's just a bank of green
It looks pretty bland from outside.
But actually, when you get inside,
I think you'll be in
for a real surprise.
Oh, wow.
Wow.
It's cathedral-like.
You come inside, and it's like being
inside a room of trees.
Yeah, it's quite special.
All you can hear is the wind coming
through that upper canopy.
And the light, this shimmering light
playing tricks on your eyes.
It's going to be good
to explore this.
This yew tree
is an estimated 1,000 years old.
It would have been a young sapling
when William the Conqueror
invaded England in 1066.
As a mature tree, it's vast
and has grown
a huge umbrella-like canopy,
consisting of millions
of tiny leaves.
One of the interesting things
about this tree
that allows it to live for so long
is that every part of the tree
is toxic
to humans, animals and birds -
so the leaves, the branches,
the bark, the wood.
The fact they're so poisonous
means yews have been linked
with death for thousands of years.
It's why graveyards are home
to many of the UK's oldest yews.
And because few creatures
can harm them,
the trees just get on
with growing bigger.
Over time, this tree's branches
have entwinned with other yews.
At more than 900 years old,
they're only now considered
mature trees.
And could live
for another 2,000 years.
But they face a big problem.
As they grow taller
and sprout more branches,
their trunks will grow wider
to support the extra weight.
Eventually, the trunks
will get so wide,
they will start to rot
from the inside out.
Unfortunately, most of the ancient
yews in the British Isles,
the centre is rotted out,
so they are hollow.
But these trees already have a plan
for extreme old age.
Yews are amazing trees,
and if you imagine that,
you know, there's the trunk
and these long sweeping branches
are the arms, or the legs,
of the yew.
Before its main trunk rots away,
this wise old tree has changed
the way it grows its branches.
Rather than growing up,
they're growing sideways
and then downwards.
This is why this huge branch,
it's come all the way
from the main trunk,
which is probably
about eight or nine metres.
And you can see here,
it's touched the ground,
and where the branch is touching
the ground, it's generated root.
So it's independent.
It's now got its own root source,
and this is a separate plant but
identical to the original parent.
Over the next few hundred years,
the tree's strategy
is to stop maintaining the old trunk
and let it rot away entirely.
The newly-rooted offshoot will
become the new trunk of the tree.
This next phase,
where the tree is growing out,
will be the second generation
of this tree.
And it will be self-sufficient
on its own root system
and will no longer need
that parent trunk to survive.
It's a fantastic thing to see.
With its new trunk, from which it
will eventually grow more branches,
this tree is essentially moving
very, very slowly.
Around a metre every century.
Most people think
that trees stay put
and they're in one position.
But they're not.
They're not static things.
This is a walking tree.
It's no longer static.
It's heading south.
So the yew tree is adapted
to be long-lived.
A tree that's been around
for a long time
and likely to be around
for a lot longer.
In a warmer corner of Europe,
there's another tree
that proves getting old
doesn't necessarily mean
slowing down.
The sun-soaked coastline
of Puglia, in southern Italy,
is the perfect place for olive trees
to thrive in their sunset years.
Antonio Antico's family has farmed
olive orchards here for generations.
Puglia produces
half of all Italy's olive oil.
40 million trees grow
in an area smaller than Wales.
Olive trees
are fantastically well adapted
to the hot and dry
Mediterranean climate.
They're evergreens,
keeping their leaves all year round.
The leaf's silver sheen
is thanks to tens of thousands
of tiny hairs,
which trap moisture
..so they stay cool
and hydrated in the sunshine.
The trees take their time,
growing extremely slowly.
So slowly,
it's thought their twisted trunks
could be shaped by the spinning
of the Earth itself.
And one gnarly beauty here
is estimated to be
more than a thousand years old.
It's believed to be one of the
oldest olive trees in the world.
So, what's its secret?
As the centuries have passed,
this tree has grown wider
rather than taller.
With its sturdy shape,
it won't topple over
in strong winds.
And being short means it's also less
likely to be struck by lightning.
Scientists have only
recently discovered
that the older trees get,
the faster they grow.
But rather than grow higher branches
that would break in the wind,
they pack on the weight
around their trunks.
And because they're bigger,
old trees are better
for our planet, too.
The older they get, the more carbon
they lock away in their wood,
so the more they're helping
to combat climate change.
Incredibly, every year,
this magnificent old stateman
bears olives.
As juicy as when it was a teenager.
After a long, hot day
in the orchard,
Antonio can enjoy olive oil
from his favourite
thousand-year-old tree.
But in the surprising world
of elderly trees,
we haven't reached the limit yet.
These are the White Mountains,
250 miles from Los Angeles
in California
..home to the oldest living trees
on the planet,
the bristlecone pines.
3,000 metres high,
this rocky terrain
is bone dry in summer
and ice cold in winter
..so the trees grow
incredibly slowly
..their trunks expanding
by just three millimetres a decade.
And rather
than using valuable energy
to grow a fresh set of leaves
each year
..bristlecone needles last
for up to four decades
..20 times as long
as most evergreen leaves.
The oldest bristlecone pines
are an incredible 4,850 years old,
making them as ancient
as the Great Pyramids of Egypt.
In the world of ancient trees,
there are even more magical places
and unique species to discover.
Ancient forests that sustain
millions of different creatures.
And we'll discover
one remarkable tree
that's been around
for hundreds of millions of years.
All over the world,
if you know where to look,
you can find
the most incredible trees.
From dragon blood trees growing
on islands in the Arabian Sea
..to something very special in the
Andes Mountains in South America
..a tree that's one
of the oldest species on Earth
..the weird and wonderful
monkey puzzle.
Expert Tony Kirkham
is at Benmore Botanic Garden
in Western Scotland
to reveal the surprising secret
behind this long-living
spiny specimen.
Wow. Now, this is another one
of my favourite trees,
the monkey puzzle, from Chile.
It is an incredible tree.
It just doesn't look real.
It looks plastic.
But believe you me, it's not soft.
And why do we call it
the monkey puzzle?
Because where it grows in Chile,
there are no monkeys.
But it was introduced in 1795
to the UK,
and as it was growing,
everyone wanted to see this plant,
and a barrister looked at this tree
and said,
"Wow, that is amazing, that would
puzzle any monkey to climb it."
And today, it retains that name -
the monkey puzzle.
If you try and touch this,
it's pretty spiky.
It is a prickly customer.
And they've got these points
on the end
that, you know, would deter
any grazing animal.
And you look at a tree like this,
with all this protection and armour,
and you think,
why does it need all this?
What animal is likely to feed
on this?
The answer is, monkey puzzles
are protecting themselves
..from dinosaurs.
These trees have been growing
on Earth for 200 million years.
Imagine if we were in this forest
200 million years ago.
These tall trees,
up to, you know, 50, 60 metres
and several thousand years old,
and imagine those huge footprints
of a dinosaur
coming into this forest
to feed on them.
These long necks that would reach up
into these canopies,
and that's why
these scale-like, reptile,
sharp, pointed leaves are there.
They've evolved for protection
from feeding dinosaurs.
Ancient trees designed
for a prehistoric world.
From one
of the planet's oldest trees,
to one of its most ancient forests.
The Amazon Rainforest
in South America
has been growing
for an estimated 55 million years.
Today, 400 billion trees
live in its tropical climate
..some of them a staggering
3,000 years old or more.
The rainforest is home
to the largest collection
of living things on Earth.
Three million different species,
many found nowhere else,
live among the trees.
5,000 miles from the Amazon,
there's another patch
of ancient rainforest.
But its location
may come as a surprise.
North West Wales.
It's looked after by the Woodland
Trust's Kylie Jones Mattock.
Well, it's got to be one of my
favourite places in the world.
It's a temperate rainforest.
But that doesn't really capture
how magical this is.
Many people really don't understand
that we have such a thing in the UK.
A temperate rainforest is a woodland
where this sort of
beautiful weather is quite unusual.
It rains.
It rains 200 days of the year.
It's believed that 5,000 years ago,
rainforests like this
covered a fifth of the whole
of the British Isles.
Now it exists
in just 1% of the country,
in precious pockets
of ancient woodland.
It's like a piece of the Amazon
in miniature in the UK.
Formed over thousands of years,
these woodlands are bursting
with life
..much of it living
on centuries-old trees.
Like this giant sessile oak.
As trees get old,
they get really exciting.
That last third of a tree's life
is when they get really interesting.
There are some really old,
gnarly specimens,
and they're really important
because they create this whole world
that supports so much other life.
Just like in the Amazon,
the twisted old trees
create a perfect habitat
for other living things
..including plants and lichens
found nowhere else in Great Britain.
The tree provides
this little microclimate,
this little micro world,
for so many other species to grow.
A single oak like this can be home
to around 2,000 different species,
busy beetles and bustling millipedes
living among its many nooks
and crannies.
To really appreciate the rainforest,
you do have to get up close
and personal.
There's a whole new world
that appears -
the textures, the shapes,
the colours.
This ancient Welsh rainforest
has thrived for thousands of years,
and it's still the perfect place
for trees to live to a ripe old age.
That sense of tranquillity,
the sense that you're also
in a really ancient place.
It's got to be one
of my favourite places in the world.
No matter how many years
a tree lives for,
eventually, it will meet its end.
But like everything
in the extraordinary long life span
of trees,
this last chapter
can span entire centuries.
So, how do trees die?
Insects can kill them.
Especially when they attack
en masse.
Extreme weather
is another common culprit.
But there's one killer that can wipe
out entire species of trees
..disease.
The south coast city of Brighton
is home to what is now one
of the UK's rarest native trees,
the elm.
Kerry Pickett is one of many locals
who treasure the precious elms
of Preston Park.
I think the thing about trees
is that they have
a very calming atmosphere.
People get something from trees
that is not actually tangible
but we all
We're all drawn to them.
I do think that people come to visit
the park to see the trees.
People call it the People's Park,
and it really is, because everyone
is so proud of this area.
Elms can grow up to 40 metres,
taller than a ten-storey building.
But a healthy tree
can live up to 800 years.
The thing about the trees
is that they're huge.
What I like
is the branches kind of look
like they're coming back down to the
earth and joining the earth again.
It has quite a distinguishable bark.
It's really crunchy.
It's very tactile.
You do want to stroke a tree
when you see it like this.
Elms used to be a common sight
across the UK.
But in the 1970s, disaster struck.
Dutch Elm Disease
wiped out 90% of Britain's elms,
over 25 million trees.
The disease is a microscopic fungus
carried onto the tree
by a tiny beetle.
The fungus blocks
the tree's circulatory system
..causing it to die
from a lack of water.
It's the job of Brighton's
Arboriculture Manager, Peter Small,
to protect the city's
precious surviving elms.
We're hugely committed
to preserving the city's trees.
It is unique in terms of diversity
and number of elms.
There is nowhere else like it
in the UK.
The key is to spot signs
of infection
before the beetle can lay its eggs.
This piece has had
all the bark stripped off.
An adult beetle will begin
a journey underneath the bark,
along this central groove,
laying eggs along either side.
In each one of these tiny lines
is a new beetle,
and then they fly on
to find the next bit of elm
to repeat the process.
They've been fighting the disease
in Brighton for over 50 years.
For more than 90% of infected elms,
the only solution is to chop
the tree down
to stop the beetle and fungus
from spreading.
I love trees.
I don't like felling them.
It's devastating.
Certainly for some people
who've grown up with these trees
since they were young.
You know, people who were born
in the city
and remember these trees
from their childhood.
And there's one tree
in Preston Park
that Peter
is particularly keen to protect.
We believe it's the oldest
English elm in Europe.
Over 400 years old.
This single ancient elm
once had a neighbour.
Together, they were known
as the Preston Park Twins.
So you can see from the photograph,
a really nice shot of the twins.
The tree on the left
was the other twin.
A few years ago, one of the twins
caught Dutch Elm Disease.
That, unfortunately,
was removed in 2019.
A tragic loss.
The hollow trunk of the felled tree
is now a poignant sculpture
for locals to remember it by.
But then, despite Peter's
drastic action, the worst happened,
the remaining twin
also showed signs of the disease.
A couple of summers ago,
there was an area
of wilting, yellowing,
on the very tips of a branch.
That was confirmed to be
a very early elm disease infection.
In an effort to save it,
Peter's team cut away a huge area
of the tree's canopy.
For now, it survives.
The remaining twin,
as you can see, is in good health.
It's a solitary twin
but, you know,
the name continues to be used.
Fortunately, it's looking healthy,
and long may it remain so.
No matter what disease
or catastrophe it survives,
the life of every tree
must come to an end.
But that's not the end
of this story.
What happens in the tree
after life is extraordinary.
Over the course of this series,
we've followed the fascinating
lifecycles of our planet's trees.
Every spring,
colour blankets the Earth
..turning to green as fresh leaves
burst from branches.
Then as summer ends,
the spectacle of autumn.
Throughout their long lives, trees
do remarkable things for our planet.
They even help us to breathe.
As leaves make sugar
to fuel the tree,
they breathe out oxygen
..the vital gas that we,
and almost every other living thing
on Earth, relies upon.
But we don't just need trees
whilst they're alive.
Once they've died,
they continue to help us
..as they return to the place
they came from,
the soil.
Scientist Cecilia Reed
follows the journey of trees
from life into death and beyond.
For many people,
trees come to mean something
very personal and precious.
So it's no wonder we grieve its loss
when it dies.
This is Betchworth Estate in Surrey,
which tends to 100,000 trees.
Most are doing well.
But some, like this oak, have died.
It's being left to decay naturally,
which means people like Cecilia can
appreciate its value after death.
We tend to think of oak trees
as pretty sturdy, strong
and resilient trees, which they are.
But just like human beings,
a few too many knockbacks
can just completely destroy them.
Its twisted branches
and scarred wood
tells us stories
of a long, hard life.
After three centuries of life,
this noble giant
recently died of oak decline.
A mix of stress, pests
and diseases overwhelmed the tree
..to a point where
it could no longer fight back.
But after death,
new life is moving in
to feast on
the two dozen tonnes of wood
the tree built up
over the centuries.
As you get closer to the tree,
it just gets more and more
remarkable.
Oak trees are known to host
the most animals
and living creatures in the UK.
But even though
this tree is no longer alive,
there are still plenty
of creatures -
bugs, birds, all kinds of species -
that are making a home here.
There are
even these small little wasps.
I can see two here
that are actually burrowing -
oh, my goodness - into the holes.
These are parasitic wasps.
They're laying eggs
into the hidden grubs of other
insects feasting on the tree.
A grizzly fate for a grub
but a sign of how much new life
this single tree will generate.
It just goes to show
how nature is definitely profiting
from this great big guy
who, even though is dead,
is still giving so much.
The hollows of a dead tree
also offer safe places
for large birds to nest.
And other new life
is also moving in.
If we look down here,
we can see hundreds of fungi
feasting away
at the base of this tree.
Life is literally finding a way
to renew it, to reuse it,
to kind of create
its own renaissance.
This striking skeleton of a tree
will soon start to lose its branches
and then, eventually, the main trunk
will fall down as well,
becoming something
we call fallen deadwood.
So, here we have
a fallen piece of deadwood,
and it does look pretty old.
I mean, the kind of rusty-like
iron colours are seeping through,
giving it this lovely autumnal
aged look.
So, this deadwood,
as we can see, it's on the ground,
it's connected with the earth,
with the soil.
Wood decomposition
is an essential recycling process
and also a really natural part
of every tree's life.
It can take 50 years
for a dead tree to fall,
and another century to decompose.
And that process takes an army
of demolition experts.
This piece of fallen deadwood
is being, bit by bit,
eaten away by bugs, basically.
And they play
a really important role
in digesting the dead tree's wood.
These bugs will then become food
for those animals, such as maybe
shrews or badgers or foxes.
So we have this gorgeous recycling
of life itself
going on right in front
of our very eyes.
Incredibly, 40% of the UK's woodland
wildlife depends on dead wood.
That's at least 5,000
different species.
This is nature's way of recycling.
The creatures feasting
on the dead tree
gradually break down every part
of this once great oak.
And the tree becomes part
of the soil beneath our feet.
A single handful of forest soil
can contain
way more living organisms
than the total number
of human beings on planet Earth.
Which I think
is absolutely remarkable.
Just as trees benefit our planet
in life,
their legacy continues in death.
Trees are a natural defence
against global warming.
The reason being is that they,
on a daily basis,
continually absorb carbon dioxide
and then they store that carbon
in their body.
When they die
and start to decompose,
it's helping to store some carbon
safely away underground,
protecting us
and the surface of our planet
from a dangerously warmer future.
I think we owe these glorious,
ancient friends a big thank you.
They are the ultimate cycle of life,
and the ultimate legacy.
We still have much to learn
about the secret lives
of many of the trees on Earth.
But as we walk
through a park in spring
..visit a much-loved
family favourite
..or stroll
through an ancient woodland
..we can stop to appreciate
their incredible inner world.
Trees are beautiful and fascinating.
Above all,
they're vital to our own lives,
to our health,
and that of our precious planet.
For more information about
the Secret Life Of British Trees,
go to the Woodland Trust at