You really are on the edge of South Downs.

Could you describe it as a natural landscape or...

So, the landscape we're driving through now is not really natural.

No.

So, these fields are arable fields, so they would normally be gray cereals, but for this year, at least they've been sown with it looks like some kind of wild seed mix.

I'm in a Jeep lurching over a dusty single track road where deep in the South Downs National Park, which is just beyond Brighton on England's southern coast.

Skylarks are taking advantage of that because they nest in the ground.

So, they're probably nesting.

You can hear them outside.

That's Ted Chapman behind the Wheel UK Conservation Partnerships Coordinator at Kew's Millennium Seed Bank at Wakehurst.

He's also my guide for today.

So, these hills that we're driving over now are all chalk, and the chalk is really close to the surface.

So, the soil here is only 10 or 20 centimeters deep and that very chalky soil, very low fertility, very sharply drained, it drains really quickly.

That's really what informs the type of vegetation that we have, and that's what makes this habitat special because these types of soil conditions and rock conditions are not found very commonly.

We're heading to Castle Hill National Nature Reserve, which is looked after by Natural England, and I'm joining Ted and his team to collect wild seeds.

Is this somewhere where you'd come see collecting a lot?

Is this an annual pilgrimage?

So, we've collected a lot of seed in Castle Hill in sites like this, because the chalk grassland supports an exceptionally diverse flora, and many of those species are highly specialized and quite rare.

So, because we're often targeting threatened species, we're often found in places like this.

The MSB's central mission is to gather wild seeds from across the globe, preserving them to safeguard the future of our planet.

This work focuses on species under threat around the world, often found in far- flung countries.

However, you might be surprised to know that some of the species most in need of protection are much closer to home.

It's just magnificent.

It's so wide and open and there's a big smudge of red down there though poppies.

Yeah, we're going to get a close- up view of these beautiful poppies.

But just as important as place is time.

In seed collecting, timing is everything.

What we're hoping for today is that our visit coincides with the precise moment the seeds are ready to be gathered, so that we can follow their journey as they're carefully processed and then stored for safekeeping in the vaults of the Millennium Seed Bank at Wakehurst.

I am Cate Blanchett, Kew's ambassador for Wakehurst, and this is Unearthed: The need for seeds.

Episode two, the present.

So, we need to get through this gate.

Yeah, I can do it.

It's the gate etiquette.

You learn that in Australia very quickly.

Oh, I see those two bars there.

So, the last thing we want is off- road bikes, off- road vehicles coming into the reserve and destroying the habitat, which would just happen so easily.

You can imagine these habitats takes centuries or millennia to evolve, but only seconds to destroy.

Yes, yeah.

Gosh, there's this team flowers, isn't it?

Yeah.

They're heavy.

They are heavier.

Are you okay with that?

And then you twist it at the top.

That's it.

Oh, great.

Okay.

Okay.

In we go.

Here we go.

We pass through multiple gates and descend into a valley.

It's wildly overgrown with shrubs and vegetation encroaching on the track.

And then as we lurch around a corner, the tree's clear and I'm greeted with the most beautiful vista.

Oh my goodness, this is magnificent.

It looks so ancient because the hills are just given away to a flat plane.

It's got a smattering of poppies.

And what's the yellow?

Is that this grass...

Man, it's so beautiful.

It's almost like someone's taken a brush with a thousand colours.

Yes, yeah.

So, the reserve is on these steep hillsides and then at the bottom of the valley, we've got this flatter area with deeper soils.

And then we've got this wash of poppies.

So, beautiful.

Something out of The Wizard of Oz.

So, if you find me asleep in there, rescue me.

So, the slope ahead of us is where we're going to be doing our harvesting today.

And this is Castle Hill itself.

You mean the green quite vertiginous- looking slope ahead of us that's got the...

Exactly.

So, we can see-

The strawberry on the top.

...

we've got the scrub at the top.

We've got this arable field at the bottom.

We've got this slightly flatter, rough bit in between.

And that area was ploughed in the second world war.

And that's why even now, it's still very different to the ancient short grassland, which is on the steep slope.

And what was attempted to be grown there?

That would've been crops for eating in that dig for victory effort.

So, these soils are with chemical fertilizers, they're quite amenable to growing things like cereals, wheat, barley, flax.

Now that farming ceased some decades ago, but even with decades of very careful management, you can see the grassland at the bottom of the slope is very different to the grasslands on the sides.

It's really green and tufty.

Yeah.

So, that is good, but we don't want too much of that.

We need a good balance.

So, what makes this spot so special apart from its incredible beauty?

It's really the quality of the chalk grassland.

So, we're going to be in one of the nicest patches in just a second.

You'll see the diversity of species and they're all tiny weeny because it's so infertile, but there are many, many species packed in.

So, we can record 40 or more species in a square metre here.

So, this is one of the most plant- diverse habitats in Western Europe on this small scale.

So, it's really special floristically and it's of course the vegetation then supports the butterflies, the other invertebrates, the birds that are associated with the invertebrates and so forth.

So, that's really why this is such a special place.

After a quick safety briefing from Ted and his colleague, Isabel Negri, UK Conservation projects officer at the MSB, we start to clamber up the hill.

We wade through some tall grasses at the bottom, but they soon thin out.

There's so many varieties of plants and I'm sure a myriad of insects all thriving underneath my feet.

We try to tread lightly in habitats like this where we can.

So, we've got into the chalk grassland.

It's very low.

And not as dense.

Much, much less dense.

And if you start looking into the sword, you can see there are lots of different species, different grasses, different species, and they're all little thistle there, a little bedstraw there, all growing intermeshed, one with another.

And underneath, you can see it now looking very dry and droughty this grey soil.

That's the very chalky alkaline soil.

So, this site is grazed by cattle.

Grazing is essential because without the grazing this would revert through scrub to woodland and the grassland would be lost.

So, that sustained grazing at the right level over centuries and centuries is what has created and maintained this landscape.

As Ted started pointing out different plants, I began to think I was getting rather good at spotting unusual species.

I should work at the MSB.

Let's head up.

We'll find...

There's always so much to see.

Yes.

It's hard not to get waylaid.

Yeah.

What's that little?

That is rabbit poo.

Oh, great.

I might put that in my pocket

So, we don't aim to collect that.

We can use it later.

Chocolate covered rabbit poo.

Here I was, thinking I'd found a rare seed rabbit poo.

Clearly, I'm not going to get a job at Wakehurst.

After my identification of the rabbit poo, we continued up the hill making our way towards some orange markers.

So, these markers mark out where we've got a really lovely population of yellow rattle.

So, yellow rattle is what we've come here to collect today.

And what's so important about the yellow rattle?

So, yellow rattle is a semi- parasitic species.

So, that means it produces its own food, but it also parasitizes other species growing with it.

And that means it reduces their vigor.

And that makes it quite important in this habitat, because it helps balance the really vigorous species against the more delicate species and allows those more delicate species to thrive.

So, it's really very important for the kind of function of the plants growing here.

It's a regulator.

It's a regulator, like a community engineer almost.

It's found in a lot of grassland sites.

We specifically need to collect it now because we've used quite a lot of the collection that we have for research work that we've done looking at the germination needs of this species.

So, yellow rattle is actually a species which has a very narrow temperature window in which it can germinate.

And so, we've done some work and Isabel has been involved in this to work out exactly what the minimum and maximum temperature range that yellow rattle needs.

And then we model that against climate change.

So, we think in 50 years' time, will the climate still provide the conditions that yellow rattle and other species need to germinate?

So, many species are resilient and they will be able to regenerate successfully in a warm climate.

But yellow rattle is an example of a species which is quite vulnerable, because it needs cold winter conditions to break dormancy and germinate.

So, it's important to understand that and start thinking about how we can manage grasslands and restoration projects to counter that and build adaptation and make sure this particularly important species survives.

So, we've used seed to support that research, so we need to replenish that seed in the seed bank.

So, we've got it for next time.

So, the first thing we're going to do is find similar rattle and take a look at it.

Some specimens here.

It's got a sort of a reddish brown stem with almost like two little pods, green pods.

That's right.

Yeah.

Will it rattle?

That's the seed rattling around and that's how it gets its name.

So, you want to collect them when they're dried?

Exactly right.

So, we want to collect seed at the point of natural dispersal.

So, that's when it's being dispersed into the environment.

That's when it's mature, it's when its longevity.

So, the amount of time it will be able to survive in the seed bank is at its greatest.

It struck me as almost paradoxical that we were gathering seeds from the very habitat where I just learned how vital they are as nature's own community engineers.

But Ted and his team work by a clear principle.

You never take more than 20% of the seeds in the field.

Each of the pods are filled with tiny seeds.

And so, our collection begins with some counting.

Okay, I make that 25 in my patch.

There's quite a lot here actually.

How many did you find?

I think about between 35 and 40 in a square meter.

Oh.

Okay.

Yeah, we average at about 20 plants per square meter.

And a little bit of maths.

I've crunched the numbers and I can tell you that we have approximately 1.

4 million seeds in our sampling area here of yellow rattle.

Yeah, down.

There's always tonnes more seed than you think there is.

And just before we start collecting, there's one more important step.

If you've got some seed in your hand, Isabel- ...

shall we see if we can do a cut test?

Yes.

Yeah.

I'll pass it to Kate.

There you go.

A cut test is used to determine whether the seeds are of good quality.

So, I'm going to give you the tools of the trade.

So, some snips, just watch yourself.

Little, they're very sharp scissors.

And so, the question is, can you grip that seed in the end of your fingertips?

Carefully slice off the top.

Am I going into the dark part of the seed?

In the dark part, yeah, right through the middle.

Nice.

And then I'll give you that lens.

And then if you hold up joy and then have a look, see if you can see-

Oh gosh.

...

anything white and flowery in there.

Well, on the edge of the seed, there's a tiny bit of...

It almost looks like someone's moved to a white pencil along the edge of it.

That's probably what it will look like is like...

Do you want to check?

It will look like a little white,

Little tiny little dots.

You see?

So, that's the end of sperm of the seed.

It's its food store.

So, sometimes we can also see the embryo, which is the little seedling waiting to come out.

And if we can see those things, it gives a clue that the seed has got the potential to germinate.

We don't know if it definitely will, but it potentially could.

If it's empty or moldy or there's a grub, then we know it's not good.

So, the cut test is a really important way we go about in the field just assessing the likely quality of the seed.

Yep.

That seed's good.

Yep.

So, yellow rattles, it's a very thin seed.

Yes.

And the bulk of it's dark.

And the bulk of it's dark.

But those white flowery bits tell me that that seed is good.

So, we've cut tested five in total, four of which were good and one of which was not good.

So, we could say for the purposes of our collection today, that about 80% of the seed here is full and good.

So, what I would do now is I'm going to take my 1.

4 million seeds in this whole population.

I'm going to work out 80% of that.

So, you've got 1, 120,000 approximately good seed in the population.

But our absolute maximum that we could collect here is only 20% of that seed, which is 224, 000 seed.

So, there's tons of seed here.

We don't need worry about depleting the natural population.

Over one million seeds are available here, an astonishing number.

To make our conservation collection, we're going to want to get 25 heads each because there are three of us collecting today.

So, we're pretty much ready to go.

We fan out, walking slowly, each of us following our own line in parallel with one another gathering as we go.

We're walking towards that orange marker.

It's fine if we wave around a little bit.

It doesn't have to be a dead straight line, but it just means that we'll cover the whole area between us.

This is when seed collecting gets competitive.

I'm trying to get a lot of heads.

There we go.

Don't be tempted to just collect the pretty ones.

No.

You want the ugly ones too.

No, that's a different one.

Yeah, it hasn't got so many heads on it.

These ones are really rattley.

I may have felt slightly competitive, but ultimately, this is a team sport.

You've actually done it.

Have I?

How many have you got?

I think I've got about 25.

Okay.

All right.

I think I've got about 13.

Okay.

Do I get the job?

Yeah.

The yellow rattle heads are scooped up into a bag, carefully labeled and a specimen is pressed.

This part of the process is now complete.

So, once we've collected the seeds, what happens now?

Where do we go?

Where do these little seeds travel?

So, those seeds would be returned as quickly as possible to the drying room at the Millennium Seed Bank.

And that's where they'll start their drying and can begin their journey through being cleaned and tested and ultimately banked.

Come on little seeds.

Later, I'll be going inside the MSB to see what happens to the seeds when they arrive at Wakehurst.

Collections like this are essential to the work of the Millennium Seed Bank, but they're carried out not just on its doorstep, but also in collaboration with partner organisations all over the world.

With a global network across nearly 100 countries, the MSB works with experts to help inform projects that will save biodiversity in myriad places.

I am Nattanit Yiamthaisong.

I am a PhD student in Chiang Mai University.

I'm working with FORRU, which is Forest Restoration Research Unit or in Thai name we call, Nuay Wichai Fuenfu Pa.

FORRU and MSB is like we are the partnership for collaboration around more than 25 years.

FORRU do the research about the restoration and we collect the seeds for sent to the MSB and I am the small part in the team for collect the seeds to send it here.

Nattanit is spending three months at the MSB as part of her PhD studying how varying temperatures influence seed germination.

We want to know if the climate change or the global warming in the future, the temperature will increase is maybe effect with the seed and germination of the seed.

We want to know if the temperature increases effect with the seed or not.

For two species from Thailand in different temperature from five to 45 degrees Celsius.

She has come to the Millennium Seed Bank to access equipment she doesn't have in Thailand.

I would like to learn about everything here because everything is new thing for me.

In Thailand, we have a lot of limitation because we don't have enough incubator, we don't have enough machine to handle with the seed.

Then I have to come here to use the facility, use the machine here.

It's like a x- ray machine, aspirator or the incubator that I have to germinate the seed.

After I finished the germination here, I have to analyze it in Thailand.

Nattanit's research allows us to understand how different seed species respond to shifting temperatures.

Knowledge that could guide us in choosing the right seeds to use for future restoration.

Her work was made possible by an MSB project called the Western Global Tree Seed Bank.

Nattanit says that their funding has inspired and opened new doors for her career.

The scholarship or the fund for the student is so good for Thai student or every student who do the research for approve the research and for learn the new things.

And everyone here is so nice.

I like everything here.

And the machine is so good, it's so new.

I think the MSB and the Seed Bank is like a treasure in the future for everyone.

It's like a hope for everyone in the future, because we don't know what happened in the future, right?

If we have the result in my hand, we can do anything in the future.

Once collected, the seeds must be carefully processed to ensure that they survive in the seed bank so that researchers both here at Wakehurst and around the world can use them for study or habitat restoration.

It's a meticulous and time- consuming process.

So, not many people get to do this.

I've been invited inside the lab in the Millennium Seed Bank to get a better understanding of how the seeds are actually banked.

And showing me around is seed curator, Sian McCabe.

Hello, Sian.

Hi.

Hey, hey.

Can you explain what are we going

Hi, nice to meet you.

to do today?

Oh, is that to clean my feet?

Yeah, yeah.

Just to make sure you're not bringing any-

There we go.

...

outdoor.

Everything's nice and squeaky clean.

Biosecurity is important at the MSB.

So, I slip on a lab coat.

Very official.

This is where the magic happens.

We've stepped into the cleaning lab, the space where every single seed is carefully freed from dust and debris and seeds that are empty or infested are removed.

But before they're cleaned, there's a very important stop they have to make.

So, this looks like a freezer, but it's more like a sauna.

So, it's 18 degrees Celsius and 15% relative humidity.

And this is really important because with every 1% a seed is dried, it can double the lifespan of the seed.

And then what do you do with say, a recalcitrant seed?

So, the seeds that won't withstand the drying process.

Yep.

So, we have other different humidity rooms.

So, this one is at 70%, so we...

Quite a big difference humidity.

So, yeah.

Sian told me that 90% of the seeds collected are what we call orthodox.

And those orthodox seeds can withstand normal drying and freezing processes.

The remaining 10% can't.

We know not to put them into the dry room and to treat them regarding...

And what's an example of a non- orthodox seed like that?

They tend to be food, so quite yummy.

So, we've got avocado and I wouldn't recommend eating it, but acorns are recalcitrant.

So, they're just a few examples.

So, there's the door.

Okay.

And this is the airlock area.

Ooh.

Through double airlock doors, we move into a cool unassuming room with every corner stacked and packed with crates.

So, we need to make sure that door's shut, that's it, before opening this one to protect our seeds.

Like Star Wars.

Yeah, if you just push it.

It resembles a supermarket store room.

Yet here, I'm surrounded by seeds from all over the world.

There's lots of plastic storage trays and there's some seeds in envelopes of South Africa, Sierra Leone, Georgia, Madagascar, they're from all over.

Greece, Ghana, Mozambique.

Goodness.

Yeah, all these crates to the right are ready to clean and to process.

Given that you've got so many seeds, I mean they all obviously need to drive for different amounts of time.

That's quite a complicated thing to matter.

Yeah.

Yeah, we have species that are super short- lived, so they're outlined at the beginning.

And with some seeds, like with the orchid seeds, we come in, we have to process within two weeks to keep the seeds alive and well.

But with most orthodox non- short lived seeds, six months seems because we have really big seeds that will take longer to drive.

So, the default position of these collections are in the dry room.

And when we get out to process them and after each process, they'll go back here to re- dry.

Once the seeds are fully dried, the next step is to clean them.

Oh, there's a rack of metal.

They look like film canisters, but they're not.

Yeah.

What goes on here.

So, these are sieves.

So, similar to what you'd have in your kitchen, but they're all different pore sizes.

So, we go from the small this end.

So, you can see here that it's a very fine mesh.

So, that's for something like dust particle seeds like the orchid I imagine?

Yeah, exactly.

Wow, I can't imagine how...

it feels so solid.

How could anything go through there?

Yeah, it's sometimes to save the seeds above it and then the dust falls behind.

And then we have the larger ones at this end.

This is for the big tree seeds, and this is what we use to get most of the bulk from the collection to separate the seeds and the debris.

There's a more high- tech solution too.

This looks like something in a fun arcade.

This machine is called an aspirator, and that uses airflow to separate the light parts of the collection to the heavy part.

Looks like you put a coin in and it will travel all the way along.

There's a almost like a big slide.

There's an opening in the top, goes into a slot, then it goes along a strange convoluted journey bit.

It's a bit like a pinball machine.

Is that to shake things off the seed or...

Yeah.

So, here's the chute.

So, it's a bit like a funnel.

We'll just turn it down so the seeds don't escape.

So, you're popping the seeds in the top, like peppercorns.

There we go.

So, in theory, the heavy parts are the good full seeds and the light parts are the debris and the empty seeds.

So, the light empty seeds get exposed to the airflow and fly over to the right- hand side.

Down the pinball machine sheet.

Yeah.

And then the heavy seeds fall down.

And that's done with air.

So, this button, you turn right to vary the vibrations of the plate to move the seeds along.

So, they're bouncing off the side of that chute and then bouncing off it, that's shaking.

You can see some bits of debris flying over onto the right-hand.

I see the air takes the light debris up and down.

So, we've got manual sieving, and this is a more high- tech version.

And then the very low- tech version is we have a rubber mat and a rubber glove.

Once the seeds have been cleaned, they are x- rayed to assess their quality.

I hadn't really thought before that a seed could actually be x- rayed.

After cleaning, it's really good to see inside of the seed to see whether there's still any empty seeds or invested seeds.

As you can see in this image, we have a few different seeds.

So, here, you can see the embryo.

So, this is the endosperm surrounding the seed.

And this is...

Tiny little thing.

This is what's going to hopefully turn it into a plant.

So, we have some really bright white images of seeds, which means that it's a solid, lovely, full content.

But here, can you see...

It's like a dark shadow in the middle

It's a maggot.

Oh.

It's a maggot?

Yes.

You've got three maggots in that batch?

Yep, but the problem with maggots is when it comes to cleaning, if you think back to the aspirator that it's all based on weight difference.

So, we can't necessarily clean out this collection because the weight of a seed with a maggot in weighs a similar amount to a full seed.

So, we try our best, but the maggots are usually not with us after six months of drying.

After being x- rayed, the seeds are counted and then taken underground to the vaults, the seed bank itself.

Downstairs?

Yes.

Sian leads me there next, descending a steep metal spiral staircase to arrive at the heart of the building concealed behind a thick metal door.

So, this is the door of the vault.

This is the door of...

And that is the longest key I've ever seen in my life.

Say about 10, 15 centimeters long.

I would say it is.

So, we just need to open the very heavy door.

Welcome in.

This is actually the most biodiverse place in the world.

In this very room?

Yeah, because we have so many species in.

So, are these technically called the vaults?

Yeah, these are the vaults where their seeds are kept at minus 20.

Oh my goodness.

It is absolutely freezing in here.

Arctic.

It feels so alien.

Almost like an old- fashioned library.

You're expecting library cards to be pulled out from these metal trays.

But along the right- hand side from meters and meters and meters are a whole lot of preserving jars, which look like the ones that I've got at home in my pantry.

Yeah.

So, the pickling jars are actually the best glass jars that we have.

And on the right- hand side, ooh, it's really icy.

On this side here, they almost look like tiny little medicine or pill bottles.

Yeah.

And so, some seeds are stored in the preserving jars and some?

It all depends on the size of the collection.

I can show you some examples in the warmer.

So, that's minus 20?

Yeah, minus 20.

I've been cold dipping, but really that is quite cold.

And how many times a day do you go in there?

Probably once or twice a week, but we had a fluffy hat with ears on to protect us, two gloves and a really big coat that makes me look 10 times the size.

But not all the seeds remain here locked away indefinitely.

When our seeds are ready to bank, we separate them into two parts.

So, we have an active part.

That's the parts that gets used for germination testing and for research and for restoration.

And then the other part, which is the base just gets left there because we're not sure.

And taking seeds in and out of the bank too often, we don't want to compromise the quality of a collection.

So, these are all glass.

So, it's really nice to see the seeds, but we're moving more onto these foil bags.

Taking up less space.

And if you drop them accidentally, they don't break.

But these new bags that you've got, look a little bit like my daughter got some astronaut's ice cream.

Oh, yeah.

That was look like it came into one of those pancakes.

Yeah, this is exactly it.

So, it's a thick foil sachet that we heat seal.

So, yeah, exactly what they have in space.

Storing the seeds is one thing, but the team here must also ensure that they can be brought back to life revived as fully fledged plants when needed.

Just as we heard in episode one, after the fires in South Australia, this process begins just a few months after the seeds are first banked and then is repeated at 5- or 10- year intervals.

It is a meticulous and monumental task.

You ready for the heat?

Oh, and here we are.

So, this is our germination lab.

Oh, wow.

The smell is really, it's very strong, very earthy.

You can tell things are growing in here.

You can really smell the soil.

These ones are growing, the clappers.

Those ones are massive.

They almost look like cockroaches, and those ones almost look like a moldy chocolate.

They're very strange and the shape of them is really varied because normally, you think about a seed as looking uniform.

Yeah, a bit like humans.

Even though we are the same species, we all look a bit different, don't we?

Really?

So, yeah.

We're surrounded by Petri dishes filled with germinating seeds.

Tiny emerging plants of every shape and size.

Some are gnarled, like potato roots, others almost otherworldly like something from science fiction.

The lab simulates day and night, 12 hours of UV light followed by 12 hours of darkness.

What's this one here?

So, this is a goat willow from Scotland.

And as you can see, it's got really good germination.

So, you can see the part that's coming out from the seed is what we call a radical.

And the cotyledons, which are the first leads coming out.

And this is really good because Salix, the goat willow, it's supposed to be super short- lived, but this has been in our bank since 2019.

So, this is five years after checking to check it's still alive-

It's still doing.

...

and it's still alive.

And so, now that all of these little goat willows have germinated, will any of those get planted out?

Only if they're needed for identification purposes or restoration purposes.

Thank you.

Thanks so much.

I've had the privilege of going inside the working spaces of the MSB and of witnessing the seed's journey from collection to germination.

But this is not a world hidden away.

Anyone visiting Wakehurst can step into the atrium here at the Millennium Seed Bank, peer into the labs, and even look down at the vault door.

What really strikes me is how these tiny, fragile beginnings hold such extraordinary promise.

I mean, each sprouting seed is a quiet guardian of our future, a small, but vital piece of the puzzle protecting our planet.

Join me next time as we look forward to the future these seeds may protect to the vision driving the final chapter of our story and the innovative science behind it.

This is Unearthed: The need for seeds.

Please follow us wherever you find your podcasts.

And hey, leave us a review so others can find us too.

And I invite you to join me in supporting the vital work of the Millennium Seed Bank by making a donation today.

You can just click the link in the episode description to learn more.

Until next time, thanks for listening.