Letter U The A to Z of TV Gardening

Hello, and welcome to the A-Z Of TV Gardening.

We are on a mission to dig up the best advice and guidance

from all your favourite programmes and presenters.

So join me as, letter after letter, one by one,

we explore everything from flowers and trees to fruit and veg.

Everything we're looking at today begins with the letter U.

Here's what's coming up.

Joe Swift goes to Germany for inspiration on urban gardening.

You know, this place is so impressive.

It's doesn't feel like high-density housing at all.

We tool up for a fight against knotweed.

It's just down here.

It's impossible to miss, it's huge!

I know. You just affect the plant you're targeting,

you don't get anything else affected.

And fatal attraction, Christine Walkden visits a garden

that is packed with poisonous plants.

I'm surrounded by a rather sinister collection of plants.

Ones that you'd do well to avoid.

That's all to look forward to, but let's begin with a gardening

family that covers a huge range of plants, flowers and even vegetables.

This U is for Umbelliferae, also known as Apiaceae.

and here's Carol Klein on why she thinks they're unbeatable.

I adore all sorts of cottage plants.

But perhaps Astrantia major is the most iconic of them all.

One of its country names is pincushion. You can quite see why.

It belongs to the Umbelliferae family, which is now called Apiaceae.

And usually the plants you associate with that are things like this Pimpinella,

with these flat heads composed of lots of tiny flowers.

But here it's got a completely different form.

And I think it's unique.

Each flower in the centre here is suspended on a little stem,

so the whole thing shakes and shivers.

And around the edge is this big circle of bracts

in which these tiny flowers sit.

And those bracts will stay there

right the way through when this has been pollinated

and each of these flowers has changed to seed.

What happens then is the seeds fall off and they sit encompassed

in these bracts until exactly the right time,

when they fall to the ground.

It does self-seed everywhere. You're always getting lovely seedlings.

In its native habitat it lives on fringes of woodland

around the edge, because what this plant adores is ample moisture

and a really good, rich diet

and dappled shade,

and that's the kind of place

where you will find it at its best in this garden too.

And as well as this lovely green and white form,

there are a whole load of others too.

Come and look at this one here.

This plant, which I've got all over the place here,

is astrantia Roma, one of the best atrantias of the lot.

It's a completely sterile hybrid,

so these plants last for ages and ages and ages.

The sort of neighbours that astrantias enjoy living with are things

that enjoy the same sort of condition.

Just look how it goes

so beautifully with things like this lovely soft Rosa mundi.

With dark-red Sweet Williams. It's lovely with crimson.

But as well as astrantia Roma,

with these very pink flowers, there's also

a whole range of very exciting astrantias in dark-crimson shades.

I love to grow those dark ones

with things like verbascum Cotswold Beauty,

and the spikes of the verbascum

are perfect with these big, soft mounds of flowers.

Try them with all manner of things.

It really doesn't matter what you put them with.

You can make them look formal,

you can make them look completely soft, relaxed, laid-back.

They're plants that everybody can use.

I'm looking for the right home for these lovely Cenolophium denudatum,

Baltic parsley,

that I picked up at Chelsea, where it was very much in evidence.

You can see immediately why this was one of the first

groups of plants to be identified as belonging to one family.

And so this seems at first to be just one flower,

if you look more closely, you can identify

the fact that it is composed of lots of these tiny little bouquets.

And if you look underneath, what a wonderful evolution.

All those stems are different lengths,

but they make sure that that plateau is as flat as a pancake.

So on different sort of levels you can get into more and more detail.

Another characteristic is the stems,

which become hollow as the plant begins to flower.

And yet another one is these ferny leaves.

In some cases they are so ferny, they are downright filigree.

One of the finest examples of this froth of foliage

is this fabulous fennel.

It's so tactile, you just feel like diving into the middle of it

and the scent...

Out of this world!

This is the opposite sort of a plant. Ow!

It's Eryngium bourgatii,

and at first sight you'd think what has that got to do with Apiaceae?

But there's always one or two members of every family

that are quite different from the rest.

I grow lots more of these from seed, from selected plants.

But every so often you get a few plants which are extra special

and the only way to propagate them

and make certain that you've got the same plant,

is to take root cuttings of them. There's a nice chunky root.

Look at that. Let's just pull this out. It's mouthwatering!

I should get several out of that,

so I won't bother with this little end bit,

but I'll take one piece here.

Just going to cut them into quite even-sized pieces,

making sure, because polarity is important,

that the bit that was closest to the crown is facing upwards in my pot.

Erngiums just adore a hot, sunny site

and they love decent drainage,

but there are some members of the family

that like the opposite kind of conditions.

Astrantias thrive on heavy, damp soil,

where they make luscious clumps. There are all manner of varieties.

The pure green and white of major, hybrids like Astrantia roma,

with these rich pink flowers and lots of glorious dark crimson shades, too.

When you get right down to it,

the structure of many of the flowers of this family

are very, very similar, but when it comes to scale,

it's quite a different matter.

These towering stems of angelica archangelica

represent one end of the scale.

There are all manner of herbs and spices,

from coriander to caraway to cumin,

not forgetting the common or garden carrot.

That's right, the green spouting part of the carrot

is a sign that it belongs to the umbelliferae family, too.

How's that for a bit of gardening general knowledge?

Still to come, city gardening,

and the undesirable plants you don't want growing near you.

But now, for something completely different,

extraordinary creations you encounter in gardening design,

because this U is for unusual gardens.

And we start by celebrating the king of unusual gardening,

Diarmuid Gavin.

This is my seventh garden in 15 years

and it just seems appropriate.

I had an idea that I thought would be exciting.

I had no particular desire to do Chelsea this year,

but it just came together as something, that...

..it was fate.

You see the empty plot and you think, "Oh no!

"I've got to dominate that and every square inch of it,"

but after a while, you start to dig and you realise nothing has changed.

As a generation of garden designers,

we have to discover something new to say.

On all sorts of different levels and for me there's no point in being here

just painting a pretty picture that I've seen a million times before.

It would be utterly pointless.

There's lots of bits of inspiration for the garden,

first of all it's coming from Ireland, but also a cinema,

Avatar, the idea of those floating islands,

with strange creatures in blue zooming past them.

Then the Giant's Causeway in County Antrim,

the stones that make this fascinating structure,

stepping up, out of the water, I love that

and also the idea of being able to be up in a garden in the sky

and almost see home.

I just love the elegance of it. I like the colour.

Seeing the colour in relation to this ribinia,

this tree that's just outside.

It's the first kind of garden association I've had with it,

so that's a bit of a thrill.

We have some trees coming today from Germany

and I'm probably a bit more excited about those trees

because they're unbelievable. Oh!

Is it a big indulgence, is it a big pink elephant?

I've caused this, I've caused a big load on a truck

and I hope it's valid.

Think about the colour.

-You won't see too much when we plant it.

-No.

What we have here is one of the feature trees of the garden,

it's a cone-shaped carpinus.

The big disks we see on the ground

are 25, 30, very large circular pools.

Based on the idea of the Giant's Causeway, of those stones

stepping up out of the water, almost up a hill,

these will be reflective pools.

The Chelsea Flower Show gave me a life.

I did my first garden here in 1995.

It's a very fair place, it's a fun place, it's a difficult place,

it's a stressful place, but I owe it everything.

So what does Chelsea owe Diarmuid?

Well, quite a lot, when it comes to publicity.

You can't have escaped the pictures of this flying pod

in the newspapers all week and the cries from some

that this isn't about gardening, it's about fantasy.

We want to be rooted in the earth!

So, is Diarmuid's garden a triumph of style over substance.

I don't think so, come and have a look,

along this snaking, rusted steel pathway,

you pass banks of trees and shrubs, very few flowers.

There's a bit of frothing lady's mantle down here

and the odd pure white arum lily over there.

The majority are grasses,

these wonderful clipped scones of box,

nudging aside the pines between them.

And up here, a sort of valley that shows you the depth

of this garden, it goes on and on, a whole flock of clipped yews,

they're just beginning to grow out of their clipping,

which gives them a pleasing, woolly texture.

There are birch trees, photinias to add stature,

but perhaps the most dramatic thing is these enormous clipped hornbeams.

Clipped into cones, some of them with foliage going right down

to the ground, others as standards.

Now, these are classy trees, and pricey ones, too.

One of these will cost you about £2,000.

They take care, time and trouble to establish.

If you're on a budget and even if you're a really good gardener,

perhaps a smaller plant, allowed to grow will give you the pleasure

of anticipating it looking like this,

but this is quality plant material

and the way in which it's all been stitched together,

around these pools, some of which are clear,

and some of which look like Irish stout, is a work, dare I say it?

Just a little flash of genius.

You look at Diarmuid, up there, standing proud in his pod,

and you think, "Is it all pie in the sky?"

"Is he flying in the face of tradition?" Yes he is, in a way.

Pie in the sky, though, it isn't,

down here on the ground, it's rooted in reality.

What remains to be seen is if the height of his medal

is as high as his aspirations, and his standard of planting.

I hope it is. I wish him well.

And there's more from Diarmuid later in the show.

Now, gardening can go on anywhere

and our next topic is for urban gardening.

Joe Swift wants our towns and cities to become more garden friendly,

so he went to Germany to see how they do things there.

I've come to Freiburg in Germany,

because it's one of Europe's finest examples of a sustainable community.

It combines high-density housing with loads of green space,

both public and private.

It's been dubbed the eco-capital of Germany and it's a huge success.

Vauban, a suburb in the city,

is a mixed tenure housing development that's home to 5,000 residents.

It has imaginative landscape architecture

and a socially-oriented policy towards public space.

Master planning was crucial in the creation of this settlement.

City planners set stringent design codes for developments,

which even private developers had to adhere to.

Unlike Britain, here, planners, architects and landscape designers

work together, contributing to each other's work and crucially,

landscape design is viewed as integral

to the planning applications, which has resulted in a high standard

of green space, both private and public.

Oh wow, look at this, this is absolutely fantastic!

A courtyard, were all the flats are overlooking

down into the central space. It's so green, it's so lush.

They've got these nice little low fences

so that you can see over into it from the outside,

but also from your neighbour's garden.

Everybody has got their own balconies at the same time.

Combined with the modern architecture,

I think it works beautifully well.

I mean, look at this, it's a bike shed and it's got a green roof on it.

It's just brilliant, the sedum on there

is going to encourage loads of bees into it,

it's going to flower, it's so much more...

It fills your soul, it makes you feel good

walking round in an environment like this

and if it was just buildings alone, it would be so grim.

Look over here, right, these lime trees,

it makes sense, in the summer, they're cooling the building

because they're all in leaf, but in the winter

when they've dropped their leaves, they let more light through,

that's when you need it, using plants cleverly, combined with architecture,

they seem to have got it just right here.

Even the tram lines for the citywide tram network

are inter-planted with grass,

and it's all part of the city's approach to environmental matters.

A stone's throw away from Vauban is the solar community area

of Schlierberg. Here, 58 timber-framed houses

have been fitted with state-of-the-art solar panels

and as a result, actually produce a net gain of energy.

A five-storey office residential and retail block

forms part of the development and provides hot water for the houses

through its solar technology.

You know, this place is so impressive.

I can't quite believe it, it doesn't feel like high-density

housing at all, because of the green spaces integrated into it.

And everybody has made an effort, they've done their bit,

they've got real pride and it's a fantastic place to live.

So, that's how it can be done, with serious design and planning.

But a bit of DIY gardening can cheer up anywhere,

as Joe Crowley found out in Liverpool.

This might look like any other alley around here,

but it's actually an oasis of green. Blooming marvellous!

In 2007, Irene Humphreys and Audrey Roberts

started turning their alleyway into a stunning garden.

And so all this, it's incredible, where did it all begin?

I came home and Irene said, "Have a look at what I've got in my back."

And I said, "It's a bath, what's that for?"

She said, "I'm going to plant flowers." I said, "Are you?"

"Where's mine? Because you can't have one without me!"

And before you know it, suddenly...

-This is what we're left with.

-You've got walled gardens.

As you can see, these are tomatoes,

last year our courgettes were about two foot long.

That bathtub is one big bouquet, basically, isn't it?

-See the honeysuckle?

-Yes I do.

-Isn't that fantastic?

That's been there for 40 years.

I completely missed that, the cistern just above it.

What was this alleyway like before, you've got to help me out,

-because all I can see is a beautiful garden.

-It was a disgrace.

A dumping ground.

Instead of putting your rubbish out for binmen,

the rubbish went into the back alley,

so we just decided to get rid of it all and start this oasis.

We've got gardens here, so this is our garden, really.

We can come out here any time.

Children can come out here, it's a safe place for them.

They come up and down on their little scooters and bikes.

One man who understands how special this place is

is chairman of Northwest in Bloom, Bill Blackledge.

They won the Northwest in Bloom Best alleyway competition

for two out of three years.

They've also won the Royal Horticultural Society certificates

for it must be five years now.

They've won so many trophies in the Liverpool area,

I've just lost count!

So what do the neighbours make of it?

-It's really good, because it makes a nice and clean.

-I like the roses.

-You like the roses?

-I like the purple ones.

Not all the neighbours are behind the project

and that's why the garden stops right here at this point.

-Gardens used to come up further.

-Right.

Until then people got fed up with that.

They were enriching the schemes.

There were hints that people didn't care

and they were the only ones who cared.

It's a personal choice, if they don't want to get involved,

there's nothing we can do about that, we have to go with the flow.

Keeping a garden like this going isn't cheap,

it cost over £1,000 last year and now the funding could be drying up.

The council has finished funding us. We're not getting funded at all.

You can't do it on fresh air, we need funding.

I couldn't imagine it not to be here, really.

-I don't even want to think about it.

-Oh, I don't.

I might have to go out and get myself a fella, to come and keep me company!

Well, for the good of him, I hope the garden stays!

THEY LAUGH

Very funny, Joe. We had you in line, actually.

Cheeky! Now, it's competition time.

The challenge? To build an urban garden worthy of the title

Young Gardener Of The Year.

So, this is it. The final challenge.

In just three hours, competitive Damian from Wigan

or green-fingered entrepreneur John from Lancashire

will be crowned the first-ever Young Gardener Of The Year.

I just want to give you a brief, and show you what I was thinking of.

Can you get us the plants off the trolley that are ours?

The rivals get straight down to choosing their materials,

planning their design and briefing their team,

in the hope that their urban garden

will blow the competition out of the water, and win them the title.

Try and keep it as simple as possible, really.

Small, circular table in the middle.

Need a gate at the front,

but I don't know how we're going to secure that.

Judges Chris and Alex will be analysing every stage

of this gardening battle.

Plus, to pile on the pressure, our finalists' friends and family

are watching their every move.

-You all right, Damian?

-No!

Let's have a look at the plans.

Damian's design includes

a circular entertainment area,

a circular lawn,

and a large set of metal gates.

I'm just trying to think of a small space,

so I've gone with a circle theme on both sides,

and try and get it as low maintenance as possible, so that's the planting I've chosen.

And then they just need to keep on top of the lawn, really. But that's why I kept it small.

And your thought process revolving around the materials?

Try and keep it a bit more rustic, really.

It's a modern couple, they've probably got a modern house,

so a bit more of a retreat, something totally different.

And just give them an escape.

Take a seat, by all means.

So, can you just talk us through your approach to this plan

and the garden?

For John's urban garden,

he's planned a winding gravel path

with a rope handrail,

large beds and a back trellis.

Taking a different slant on urban.

-Right.

-It is very low maintenance

because they've got quite a hectic lifestyle.

Can you justify the choice of your materials?

It's urban, but you could say it's urban, brinking on the edges of rustic.

But I'm hoping, with all the gravel, bricks, a lot of hard materials,

to soften it up with the planting. So I'll be very focused

on the choice of plants we're going to use.

Throughout the contest, competitive Damian's creative skills

have beaten his opponents' hands down.

With these, do you reckon I should just screw them to this board?

Less than an hour into the challenge, his gates are up

and he's already laying the turf for his circular lawn.

Like laying a carpet. Look at that!

Although the grassroots gardener's plant knowledge

has been unbeatable in every round,

John's creative flair has been severely lacking

throughout the competition.

-And if you can put two more in.

-Same?

-Yeah, please.

But, having painted the backboard a fresh blue,

and with his winding path starting to take shape,

John's garden is poles apart from his rival's design disaster.

You're at the halfway mark, guys, you've got about an hour and a half to go.

With the clock ticking until our judges crown the first ever

Young Gardener Of The Year,

our contenders' empty plots

are being totally transformed into stunning gardens.

We want to fill it up.

John's team are busy filling beds with bark.

Yeah, keep it coming.

While his attention is fully focused on climbing a jasmine up his back trellis.

DAMIAN SIGHS

Damian's team have constructed an archway,

to divide his controversial circular areas.

The fences are up, and his lawn has completely taken shape.

You got 20 minutes to go, guys. 20 minutes left.

With only minutes left until the judges choose their winner,

the rivals pick up the pace and push their teams for perfection.

Put that back in that barrow.

-I think it's neck and neck at the moment.

-Really?

I certainly think John has gone not for that show impact at all.

The back of it looks a bit sparse. And how is he going to view that in the future?

Damian has produced some crazy combinations of plants.

I'm so worried about them.

He's got cotinus next to fatsia, and they're cheek by jowl.

That is just not going to work.

-It's just...

-SHE GROANS

OK, guys, five,

four,

three, two,

and one. Time's up.

APPLAUSE AND CHEERING

Two very different gardens, two very different contenders,

but who will be the first ever Young Gardener Of The Year?

Damian, John, it's been a tough contest,

but only one of you will be going home as Young Gardener Of The Year.

Before we find out which one of you that's going to be,

-I'd like to get some feedback from the judges.

-Damian, you were strong and brave in your design,

and you took risks, which I liked. Keep working on your plant knowledge,

and remember, plants don't sit still, they move and they grow.

Well, John, you have constantly wowed Chris and I

with your plant knowledge, but what has thrilled us most

is your growth in your design work in this competition.

Still lots to improve, but you're well on your way.

OK, guys, crunch time.

This is it, the first ever Young Gardener Of The Year is...

It's John.

APPLAUSE AND CHEERING

John's outstanding plant knowledge blew the judges away.

Now, most of the plants we show you on the A To Z Of TV Gardening

are things of beauty, for you to admire and desire.

But not all. Because our next U is for Undesirable Plants.

Those you'd normally want to avoid outright.

Christine Walkden's found a very good place to get us started.

Alnwick Castle in Northumberland, built in the 11th century,

and now home to a very unusual garden.

I'm surrounded by a rather sinister collection of plants -

ones that you'd do well to avoid.

Eating this can cause an agonising death.

Just a taste of this can make you vomit,

and this plant contains one of the most toxic chemicals known to man.

Welcome to the Poison Garden.

This garden is so dangerous, the gates are kept locked.

It's monitored round the clock,

and visitors are not allowed in without a guide.

All this is down to one woman - the 12th Duchess of Northumberland.

She's been fascinated by poisonous plants for 15 years.

Jane, why are you so passionate about poisonous plants?

The same plant almost always kills and cures.

And I saw gardens around the world, mostly which were apothecary gardens,

and I just thought, this is a bit boring, let's try and do it differently.

Let's focus on the kill rather than the cure.

There are some notorious killers in here,

such as belladonna - Italian for "beautiful woman",

but you'll know it by another name.

Deadly nightshade is one of the biggest nasties here,

and if you were to eat just one leaf, it could kill you.

But centuries ago women used it as a beauty aid, in the form of eye drops.

This plant contains atropine, which paralyses the muscles in the eye.

So the eye drops dilated the pupils, making them appear more attractive.

But overuse of belladonna could cause blindness.

Jane, which plant turns you on the most?

The datura without a doubt.

Beautiful, beautiful flower,

but every part of the plant is poisonous.

Datura was used by the Aztecs to prepare human sacrifices.

It would leave their victims numb to their gruesome fate.

You have to take special precautions in this garden.

Gloves are essential. A little while ago one of the gardeners had blisters all over their arms,

caused by the sap of this plant, known as rue.

Otherwise known as ruta graveolens,

rue causes light-sensitive burns which can flare up whenever they're exposed to the sun.

The Duchess has sourced her plants from all over the world.

This is the castor oil plant, a native of India,

but I used to have to take the oil of this as a kid,

and it tasted just like poison!

It is. It's disgusting. Revolting smell. But once you've extracted the oil,

-you're then left with a really poisonous residue.

-Right.

You then have a really strong and very potent poison,

and there's no antidote to that.

The plants have really developed their strengths

to keep away their natural enemies - insects, not really us -

and it's how we've decided to use the plants to suit our means,

and that's where we've had trouble.

This is obviously a labour of love.

I love this garden. I love the stories about poison.

When I'm dead, I'm going to have some of my ashes scattered here,

probably against one of the walls,

and I plan to come back and haunt this garden and keep an eye on it!

I'm normally at my happiest when I'm surrounded by plants,

but this Poison Garden leaves me on edge.

But it is absolutely fascinating.

It's not just deadly poisonous plants that are undesirable -

here's Christine with more.

In this community garden behind me lurks something quite sinister,

which is wreaking havoc across the UK.

Believe it or not, it's this, fallopia japonica,

commonly known as Japanese knotweed.

The nearest thing to Godzilla in the plant world.

Native to Japan, it was introduced into the UK by the Victorians as an ornamental plant.

But it soon escaped, and it's now romping across the UK.

Listed by the International Union For Conservation Of Nature

as one of the world's 100 most invasive species,

Japanese knotweed swamps all over vegetation in its path and can even burst through tarmac.

It grows incredibly quickly, over a metre in three weeks,

and is now so prolific that there's not a single six square mile in the country

where it's not found.

If you've ever tried to eradicate this Triffid-like plant, you'll know how difficult it is.

Complete removal methods are both difficult and expensive,

and currently cost the UK an estimated £150 million a year.

And it's incredibly easy to spread knotweed -

all it takes is a pea-sized root fragment to infest an area,

like this site in West Horsley, Surrey.

It appears to me it's likely to have come in on that rubbish.

We've marked it all off,

so that people don't keep walking in and out here

cos if we just take a little bit away on our boots

without checking them when we leave,

we could have it all over the rest of the garden.

Absolutely. Well, I think that's the problem. People don't recognise it,

then don't know how to deal with it and don't realise that

the tiniest little bit in a bit of rubbish like a dump

can then infect your land. So what have you done so far to control it?

Well, last autumn we had a spray in here,

and as you can see,

this spring it's come back as if nothing had happened.

To eradicate the knotweed for good,

the community have had to call in an environmental consultant.

So why is Japanese knotweed so incredibly difficult to remove?

Well, you've got underneath this stand of Japanese knotweed

a massive underground root system which we call rhizomes.

Typically on a well-established stand like this

you'll have roots going down at least two metres deep,

and they will spread laterally,

normally within two to three metres of any visible plant.

So why can't I just dig it up and throw it in my dustbin?

Well, because Japanese knotweed is classified as a controlled waste,

and therefore all the Environmental Protection Act requirements

apply to this plant.

Knotweed's destructive force is now gaining the attention of homeowners,

as some High Street banks are declining mortgages

on properties infested with knotweed.

To finally rid the community garden of knotweed,

Nic and his team have had to extract and sift tons of infested soil.

'This costly method is effective, but researchers at CABI,

'an agricultural research organisation,

'are hoping they've found a natural solution to the knotweed problem.'

So what research have you been doing here?

Well, we've been going back to the area of origin of the plant,

which is surprisingly Japan,

and trying to find the natural enemies that feed on it

and might have a potential for controlling it here.

In Japan there's almost 200 species feeding on it,

and our job was to find which of those might be suitable.

It's vital to find a predator which feeds only on knotweed,

so it does not damage other British plants and wildlife.

It's a process of elimination choosing the agent -

we had to reject 199 of those organisms to find the one that does feed on it, aphalara itadori,

this is this little psylid, and these psylids suck the sap from the plant,

or at least their young do.

This is the damage caused by a group of nymphs just feeding at the base here,

but what you can see here is these tiny leaves,

and those leaves won't get any bigger.

So that plant is not going to be performing well if it had loads of leaves like this.

It ends up with the plant suffering quite significantly.

-So it's basically stunting it.

-Effectively, yeah.

The Government have now granted a licence for a controlled release of this natural predator.

In the time being, if you're under attack from Japanese knotweed,

call in the experts.

If tests with natural predators go well, we could soon have a method of

controlling this super weed,

saving the economy millions of pounds a year.

Thanks, Christine. Now let's join Helen Skelton,

who's with Sam Bull from the Wildlife Trust,

for a case of same undesirable problem, different solution.

Right, here we are.

This is the serious work.

This is the serious work.

We've got Japanese knotweed all around us.

Because we're doing injection using pesticides,

I've got to get my kit on.

I've got this lovely white suit.

You can carry the bucket.

You've cut all this back yet it still seems to be growing really well here.

We cut this back about a month ago to help control it,

but, as you can see, this is all grown up within a month.

You can see how fast it grows and what a problem that is.

If it crops up in your garden, how do you get rid of it?

Act as quickly as you possibly can. The longer you

leave it, the more expensive it gets to treat

and the more difficult it can be to get rid of.

-It's like something out of Day Of The Triffids.

-Yes, a bit.

'What Sam is doing today is far more hardcore than pulling up

'a few roots.

'This is chemical warfare.'

It's just down here.

-It's impossible to miss. It's huge.

-I know.

This is the area that couldn't have been chopped down.

We're going to treat it today using the injection guns.

How effective is the injection?

It's really effective because the spraying,

you're landing the spray on the leaves

and you are not always going to get 100% take-up by the plant.

It's so much better for wildlife because with injecting,

we're getting the chemicals straight into the stems

and nothing that's surrounding us will be hit by any chemical.

You just affect the plant that you're targeting.

You don't get anything else affected.

It's fairly simple.

We just need to inject between the first node, which you can see

is the ring around the stem here.

And the third node. This one up here.

We need to get the chemical in there.

It's just a simple push in there and an injection.

That one is done.

There is a little hole halfway down the needle which shoots

-the chemical down into this stem.

-How long does it take to die?

You can see the effects between almost immediately

and in a few weeks' time.

Because we use a dye in the chemical,

you will see the stems turn blue and you can see it, the colour

moving down as it takes the chemical down into its root system.

It can be worrying for people. They pass stands of blue knotweeds,

we put up a sign saying to people that it's been treated

so don't worry about it.

We've seen how quickly it grows. Do you think we'll ever get rid of it?

I think, on this site in particular, yes, if we persevere with this

and keep visiting it, year-on-year, we'll be able to eradicate it.

-What about the rest of the country?

-It depends on everyone else.

I think countrywide is a big task.

We end today with a return journey to the unconventional world

of Diarmuid Gavin.

And Alan Titchmarsh is looking at his entry

for the 2012 Chelsea Flower Show.

Alliums and hostas, silver birches and rhododendrons,

a swing and scaffolding.

It's gardening, Scotty, but not as we know it.

It's had Chelsea pensioners stacked up its outside

and ladies shrieking as they come down that steel chute to escape.

It's Diarmuid's magic pyramid.

Enough of the flummery. What's it all about?

-There must be a serious point to this as well. Isn't there?

-There is.

It is exploring the notion of a multi-storey garden

in an increasingly urbanised society.

Lots of people live in cities like London.

There's not a lot of green space.

It is an experiment in gardening,

lots of people gardening on top of each other.

You reckon this could work on a tower block?

It's a scaffolding pyramid that could be permanent in a plaza.

We've created, from a 16-by-16 metre base, 576 square metres of usable

garden space.

If there is enough light coming in, I don't see why not.

Let's go and have a look. Let's go and look at it.

This is a fabulously padded swing seat. I'm reluctant to leave it.

-Past the shed.

-Past the practical garden shed.

We've lots of sheds, lots of water.

We want to show sustainable gardening.

We come up to a communal terrace, which is the meet and greet area

where everybody who gardens here would come together.

-How many floors altogether?

-Seven different floors.

-Wow.

Residents' members' club.

I'm not a member. Am I allowed in?

-You are a member now.

-Oh, look.

Oriental style pavilion that's half Irish cowshed, half...

It's rustic in nature

and we have this circular opening leading into a secret garden.

You walk into a secret garden. It is magical.

You just disappear from one area into another.

-It's a garden that keeps you moving.

-It does.

I love this sort of treetop bamboo walk.

They shoot up, then the black ones start from here.

You walk past this shady plant and rhododendrons

and walk up around the pink shade to another level.

-There is a pond here!

-The roof of the shed collects water.

It's used in the washing machine.

You do your washing as you're gardening and you hang it out to dry.

-Good drying day.

-Very good, isn't it?

-It's your washing, it really is, isn't it?

-It is.

Fir tree, elevated on the fourth floor. Rosemary, thyme.

Good light levels up here.

We have the Victorian style greenhouse

and these old industrial containers used to plant our fruit and veg.

-Which level are we on now?

-On four, about to go to five.

Vegetables going up.

So you wash your clothes down below and your body

-and do your ablutions up here?

-That's right.

This is a shower and a bath. The water is collected.

It's fed to a barrel down below and used for the fruit and vegetables.

I needn't have stayed in a hotel!

I could've stayed here in your pyramid.

-You could have lived here.

-Magical. Are we still going up then?

-One more?

-Yeah.

-Two more?

-Up and up and up.

-Great vantage point.

-Across the river.

-Absolutely.

From here, I can see what you have for breakfast.

From here, a lot of people would see their own breakfast.

Getting very high.

It's rather fitting that,

on top of your 80-foot pyramid, is a plant and it's a fabulous birch.

Wonderful peeling bark. Which one is it?

It's a beauty, a heritage. It has fantastic bark.

We wanted to crown it with a plant.

It's in a bed of billowing Mediterranean-style planting.

There is full sun so I think it's going to enjoy it here.

There could not be a better day to see this. It's absolutely wonderful.

The London skyline around us.

The bridges into London and Battersea Power Station. Well done.

It's a lovely job. Congratulations.

Unusual but wonderful. I hope you enjoyed that.

Do join us again on the next A-Z Of TV Gardening. Goodbye.

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