0:00:02 > 0:00:07For centuries, our relationship with weeds was one of peaceful co-existence.
0:00:07 > 0:00:13We tolerated them in our gardens and fields as part of the natural order.
0:00:13 > 0:00:17Weeds can be useful to us as well as beautiful.
0:00:17 > 0:00:19But they're more than that.
0:00:19 > 0:00:23They're a vital resource for insects and wildlife.
0:00:23 > 0:00:29They can help us unlock mysteries about the entire plant kingdom.
0:00:29 > 0:00:34And they're key to maintaining the most basic processes of life on Earth.
0:00:34 > 0:00:38'Having worked as a professional gardener for the last 20 years
0:00:38 > 0:00:40'at Kew Gardens, Edinburgh Botanics
0:00:40 > 0:00:44'and Westminster Abbey, I've fought a low-level war
0:00:44 > 0:00:49'against those plants which I condemn as weeds.'
0:00:49 > 0:00:53I've probably condemned thousands of plants to the compost bin
0:00:53 > 0:00:54over the last two decades.
0:00:56 > 0:00:58'But now I'm starting to wonder
0:00:58 > 0:01:01'what turned me against them in the first place.
0:01:01 > 0:01:06'After all, we've always made good use of them in natural remedies.'
0:01:06 > 0:01:09It's used for joint problems, arthritis and rheumatism.
0:01:09 > 0:01:11Hoo!
0:01:11 > 0:01:14'Today's problems really started
0:01:14 > 0:01:18'when we began to bring in non-native wild plants from abroad.
0:01:19 > 0:01:23'Many of these plants looked pretty appealing at first,
0:01:23 > 0:01:26but there was one small problem.'
0:01:26 > 0:01:29This is one of the most invasive species in Britain today.
0:01:29 > 0:01:34Each one of these racemes is capable of producing hundreds of seeds.
0:01:34 > 0:01:38'We ended up throwing everything we could into the fight against weeds,
0:01:38 > 0:01:41'a battle I've been part of myself.'
0:01:44 > 0:01:48Applying a poisonous emulsion, it works 40 acres a day...
0:01:48 > 0:01:51But ultimately, it's a war I will lose
0:01:51 > 0:01:54as these hardy, opportunistic plants
0:01:54 > 0:01:59have inventive ways to make sure they survive in the natural world.
0:02:00 > 0:02:03'In turning them into enemies,
0:02:03 > 0:02:06'we forgot what they can be like as friends.'
0:02:06 > 0:02:08We see them as vegetable trash.
0:02:08 > 0:02:13They're like maggots or vultures. There's more and more all the time.
0:02:13 > 0:02:15'Time to repair our relationship
0:02:15 > 0:02:19'with these humble, but essential plants before it's too late.'
0:02:31 > 0:02:35'In the last 50 years, there's been an all-out war on weeds.
0:02:38 > 0:02:42'The weeds have got tougher and so have the weapons.
0:02:44 > 0:02:46'It wasn't always like this.
0:02:48 > 0:02:52'Out in the countryside, weeds, if they weren't exactly our mates,
0:02:52 > 0:02:54'were part of the natural order.
0:02:57 > 0:03:00'People thought weeds were something we'd lived with
0:03:00 > 0:03:03'since we got kicked out of the Garden of Eden.
0:03:03 > 0:03:05'But then something came along
0:03:05 > 0:03:09'which made weeds feel very unwelcome.
0:03:10 > 0:03:12'Gardens.
0:03:12 > 0:03:17'Once, gardening was a pastime only for the aristocracy,
0:03:17 > 0:03:18'but in the 19th century,
0:03:18 > 0:03:22'new red-brick terraces sprang up across Victorian England.
0:03:22 > 0:03:26'And they all came with their own little garden.
0:03:26 > 0:03:29'For the first time, every British man and woman
0:03:29 > 0:03:33'could control nature for artistic effect.
0:03:33 > 0:03:38'The chance to impose order on the natural world really caught on
0:03:38 > 0:03:42'and now no-one loves their gardens more than we do.
0:03:42 > 0:03:45'This is our own precious patch of ground,
0:03:45 > 0:03:48'where weeds are strictly not invited.
0:03:50 > 0:03:55'We've been firmly told there's no room anywhere for weeds.'
0:03:55 > 0:03:59These are the seeds of annual weeds.
0:03:59 > 0:04:02They will compete with my seedlings for light and moisture
0:04:02 > 0:04:05unless I do something about it.
0:04:06 > 0:04:09'But what we haven't been told is that the more we struggle
0:04:09 > 0:04:13'to keep them out, the more the weeds will come back.
0:04:13 > 0:04:17'They move in like an invading army.
0:04:17 > 0:04:21'They are plants that thrive where we least want them.
0:04:21 > 0:04:25'We think of them as intruders from an alien world.'
0:04:29 > 0:04:31Monster plants on the march!
0:04:32 > 0:04:35'The irony is, there'd be no such thing as weeds
0:04:35 > 0:04:38'without our very efforts to get rid of them.
0:04:38 > 0:04:42'And it's taken me a long time to realise why.
0:04:43 > 0:04:48'My personal relationship with weeds started with my formal training.'
0:04:48 > 0:04:51When I was a student here at Edinburgh Botanics,
0:04:51 > 0:04:54I was sent out to defend these plants.
0:04:54 > 0:04:57One of my foes was this little chap here -
0:04:57 > 0:05:00Cardamine hirsuta or the bittercress.
0:05:00 > 0:05:02I begrudgingly admired this plant,
0:05:02 > 0:05:06because I'd get my tweezers and pick it out of the ground,
0:05:06 > 0:05:10but as I did it, I found out it had an exploding seed head.
0:05:10 > 0:05:14It was almost as if I pulled it out and the seed shot everywhere,
0:05:14 > 0:05:17it was saying to me, "I'll see you next week."
0:05:24 > 0:05:27'When I left Edinburgh, weeds were still my enemies.
0:05:27 > 0:05:29'It wasn't until I took over at Westminster Abbey
0:05:29 > 0:05:32'that I saw things differently.
0:05:32 > 0:05:35'Although weeds seem like the lower orders,
0:05:35 > 0:05:38'they're not going to be pushed around by anyone.'
0:05:40 > 0:05:43When I first came here as Head Gardener,
0:05:43 > 0:05:46following in the footsteps of nine centuries of gardeners,
0:05:46 > 0:05:48I knew it was a special place.
0:05:48 > 0:05:51The first real event I was to experience
0:05:51 > 0:05:53was a celebration of the Battle of Britain.
0:05:53 > 0:05:55The great and the good came along -
0:05:55 > 0:05:57a sovereign, lords and ladies,
0:05:57 > 0:06:01Knights of the Order of Bath, politicians and our veterans.
0:06:01 > 0:06:03In such esteemed company,
0:06:03 > 0:06:06I developed an obsession with weeding.
0:06:09 > 0:06:12'The truth is that the more we try to get rid of them,
0:06:12 > 0:06:15'the more they come back. That's what they do.'
0:06:15 > 0:06:20What I learnt was that weeds are rebels. They adhere to no boundaries
0:06:20 > 0:06:23and conform to no rules. The fact that they did that
0:06:23 > 0:06:26within the walls of the establishment led me to have
0:06:26 > 0:06:28a great sense of admiration for them.
0:06:35 > 0:06:38'To me, weeds' willingness to grow everywhere and anywhere
0:06:38 > 0:06:44'represents regeneration and new life, surely something to celebrate.
0:06:58 > 0:07:03'I think we've forgotten what a weed is and what it does,
0:07:03 > 0:07:06'what makes it so special, so I'll start at the very beginning.
0:07:07 > 0:07:08'What is a weed?
0:07:08 > 0:07:13'Surely there must be an official definition?
0:07:13 > 0:07:16'Gardeners' Question Time organic gardener Bob Flowerdew
0:07:16 > 0:07:18'has always championed the plants
0:07:18 > 0:07:21'most people think of as useless weeds.'
0:07:24 > 0:07:28All the textbooks will say a weed is a plant in the wrong place,
0:07:28 > 0:07:31which is fairly true.
0:07:31 > 0:07:34They're not as pretty as the flowers you want to cultivate,
0:07:34 > 0:07:35or they're not as productive.
0:07:35 > 0:07:39Would you want carrots or weeds choking them all?
0:07:39 > 0:07:40You want the carrots.
0:07:40 > 0:07:43- Weeds are this potential resource. - Yeah.
0:07:43 > 0:07:49Most, all of our garden plants were once weeds. They were wild plants.
0:07:49 > 0:07:50And we've improved them,
0:07:50 > 0:07:54first, by giving them better culture and by selection.
0:07:54 > 0:07:59- Botanically, there's no such thing as a weed.- There's no difference.
0:07:59 > 0:08:02It is just a plant that we haven't discovered the virtues of yet.
0:08:02 > 0:08:06When I started gardening, on the parks, it was very meticulous -
0:08:06 > 0:08:10pruning the hybrid tea roses, edge the green, stripe the lawn.
0:08:10 > 0:08:13Have attitudes to weeds changed? We're more relaxed?
0:08:13 > 0:08:18There's a time for everything. Some people love a neat garden.
0:08:18 > 0:08:21However, they won't have as many butterflies, hoverflies
0:08:21 > 0:08:24and other interesting things as they haven't the resources.
0:08:24 > 0:08:28They also will have bare soil and have to buy in fertiliser.
0:08:28 > 0:08:33It's bizarre, but they're throwing away what makes fertility for free.
0:08:33 > 0:08:37- So they have a place in your garden? - Oh, very much so.
0:08:41 > 0:08:45'There are over 40 different definitions of a weed,
0:08:45 > 0:08:47'but none of them is definitive.
0:08:47 > 0:08:51'They're all really descriptions of our attitudes to weeds,
0:08:51 > 0:08:52'not botanical categories.
0:08:56 > 0:08:58'Calling a weed unattractive or unwanted
0:08:58 > 0:09:01'makes sense if you're a suburban gardener,
0:09:01 > 0:09:05'but not if you want to look at the plant kingdom as a whole.
0:09:05 > 0:09:10'Richard Mabey has been writing about wild plants and weeds
0:09:10 > 0:09:12'for the last 30 years.'
0:09:12 > 0:09:16Well, there have been masses of definitions.
0:09:16 > 0:09:19In America, a weed is any wild plant
0:09:19 > 0:09:23which grows six inches above the ground in a garden and it's illegal!
0:09:23 > 0:09:26Somebody, an American writer, Ralph Waldo Emerson,
0:09:26 > 0:09:29said a weed is simply a plant
0:09:29 > 0:09:33for which a use has not yet been discovered.
0:09:33 > 0:09:38The most popular one is that a weed is a plant in the wrong place,
0:09:38 > 0:09:42but that means somebody's got to decide what the right place is.
0:09:42 > 0:09:48'To show me the difference between a right place and a wrong place,
0:09:48 > 0:09:52'Richard took me to the 12th-century abbey at Bury St Edmunds.'
0:09:52 > 0:09:54There's a very graphic illustration
0:09:54 > 0:09:58of the extent to which there are minute differences
0:09:58 > 0:10:01in what can be the right and wrong place for a plant.
0:10:01 > 0:10:04Here we've got Aubretia in the wrong place in two ways.
0:10:04 > 0:10:10It's a native wild flower of southern Europe, brought into this country
0:10:10 > 0:10:11as a rockery plant.
0:10:11 > 0:10:15It's escaped onto the walls of the abbey where it's tolerated
0:10:15 > 0:10:19only if it's about five feet above the ground. If you come down here,
0:10:19 > 0:10:24the Aubretia has been the subject of weed killer spray.
0:10:24 > 0:10:27It injects so much subjective opinion into it.
0:10:27 > 0:10:31Some people, if they get bluebells in their garden,
0:10:31 > 0:10:35you know wild bluebells from the outside, regard them as a weed
0:10:35 > 0:10:38because they should stay in the woods where they belong.
0:10:38 > 0:10:42And conservationists regard the Spanish bluebell,
0:10:42 > 0:10:45a slightly bigger, more aggressive sort that people grow,
0:10:45 > 0:10:48when that gets out and into woods and hybridises with the English bluebell,
0:10:48 > 0:10:50THAT'S a weed!
0:10:50 > 0:10:55So there's enormous kinds of social and convention and even fashion
0:10:55 > 0:10:58which come into this definition.
0:10:59 > 0:11:02'If the definition of a weed just depends on fashion,
0:11:02 > 0:11:05'then you can bet that what counts as a weed
0:11:05 > 0:11:09'has changed again and again over the last 300 years.
0:11:09 > 0:11:11'In fact, the story of our changing attitude to weeds
0:11:11 > 0:11:14'is really the story of our changing attitudes
0:11:14 > 0:11:16'to civilisation and nature.
0:11:20 > 0:11:24'In the 18th century, buccaneering plant hunters set sail
0:11:24 > 0:11:28'in search of new non-native wild plants.
0:11:29 > 0:11:33'One of their prize discoveries was Senecio squalidus,
0:11:33 > 0:11:38'commonly known as Oxford ragwort and, today, a confirmed pest.
0:11:39 > 0:11:42'It started life as a native wild flower
0:11:42 > 0:11:44'on the slopes of Mount Etna in Sicily,
0:11:44 > 0:11:49'where it had thrived on the volcanic clinker.
0:11:49 > 0:11:52'It was brought to England and arrived in Oxford in the 1700s,
0:11:52 > 0:11:55where it was studied carefully.'
0:11:55 > 0:11:57Its first recorded point of arrival
0:11:57 > 0:12:00was here at the Botanic Gardens in Oxford,
0:12:00 > 0:12:03hence its name. It was either brought by collectors
0:12:03 > 0:12:05or snuck in on the root ball
0:12:05 > 0:12:08of one of the many plants being collected at the time.
0:12:08 > 0:12:13'It was recorded by Joseph Banks, the great 18th-century plantsman,
0:12:13 > 0:12:17'as growing within the garden quite happily in the 1770s.
0:12:19 > 0:12:23'By the turn of the century, seeds found their way into the walls,
0:12:23 > 0:12:27'the lime of the mortar suiting their taste for a high pH.
0:12:28 > 0:12:31'But it wasn't long before the plant escaped
0:12:31 > 0:12:33'and spread throughout Britain.
0:12:34 > 0:12:37'The seeds wafted over the walls,
0:12:38 > 0:12:41'down the lanes and past the colleges,
0:12:41 > 0:12:44'past the Sheldonian Theatre.
0:12:46 > 0:12:50'By 1830, the plant had arrived at Oxford railway station.
0:12:52 > 0:12:55'The dry rocky shingle used as ballast along the railway line
0:12:55 > 0:13:00'soon became a home from home for the newly-escaped ragwort,
0:13:00 > 0:13:03'mimicking perfectly the conditions it would have enjoyed
0:13:03 > 0:13:06'in its native land.
0:13:12 > 0:13:17'As well as getting on board via the soles of passengers' shoes,
0:13:17 > 0:13:21'the seeds were also carried along by the trains' slipstream.
0:13:24 > 0:13:28'And as a result of all this help from the wind, trains and humans,
0:13:28 > 0:13:32'Oxford ragwort spread quickly around the entire railway network.
0:13:35 > 0:13:40'But if the 18th century was the great age of plant hunting
0:13:40 > 0:13:42'in the name of science,
0:13:42 > 0:13:45'by the 19th century, our attitude had changed again.
0:13:48 > 0:13:52'Victorian plant hunters looked, above all, for colour and drama
0:13:52 > 0:13:56'and they didn't worry about what mischief the plant might do
0:13:56 > 0:14:00'in the temperate, accommodating climate of Britain.'
0:14:00 > 0:14:03- Any idea of what it is? - No, not really.
0:14:03 > 0:14:07A foreign import of some sort. I know not what of.
0:14:07 > 0:14:12'Little did they know that many of the plants prized for their beauty
0:14:12 > 0:14:15'would, years later, be vilified as pests.
0:14:21 > 0:14:24'And when exotic plants were brought back from abroad
0:14:24 > 0:14:26'by our 18th-century forebears,
0:14:26 > 0:14:31'no-one gave a thought to the effect they might have on native species.
0:14:31 > 0:14:34'Three plants in particular,
0:14:34 > 0:14:37'highly prized as ornamental blooms in the 19th century,
0:14:37 > 0:14:39'are now officially blacklisted as plant pariahs
0:14:39 > 0:14:42'to be hunted down and exterminated.
0:14:45 > 0:14:47'And each of them tells us something different
0:14:47 > 0:14:50'about our changing relationship with weeds.
0:14:52 > 0:14:56'Buddleja Davidii, or the butterfly bush, came from China,
0:14:56 > 0:14:59'the first of these aggressive plants brought into Britain
0:14:59 > 0:15:01'that have since escaped from our gardens
0:15:01 > 0:15:04'and into places that remind them of their native land.'
0:15:06 > 0:15:09This is one of the most invasive species in Britain today.
0:15:09 > 0:15:13Each of these raceme is capable of producing hundreds of seeds.
0:15:13 > 0:15:16A plant like this would produce thousands,
0:15:16 > 0:15:20each one capable of germinating in ballast, mortar or even concrete.
0:15:24 > 0:15:25'Like Oxford ragworts,
0:15:25 > 0:15:30'Buddleja feels completely at home along the rocky railway tracks,
0:15:30 > 0:15:33'where it has spread the length and breadth of the country.
0:15:33 > 0:15:36'Preventing these plants damaging
0:15:36 > 0:15:39'and of the thousands of miles of Britain's railway lines
0:15:39 > 0:15:42'is a costly process for Network Rail.'
0:15:43 > 0:15:46Neil, a big weed problem. How much is it costing?
0:15:46 > 0:15:52To deal with the weeds on the track, every year it's £3-£4 million.
0:15:52 > 0:15:55To deal with all the vegetation on the network,
0:15:55 > 0:15:59dangerous trees and the weeds, £30-£40 million.
0:15:59 > 0:16:04- And I suppose one of your biggest problems will be Buddleja.- Yes.
0:16:06 > 0:16:10I know these come from China where they're on lime cliff faces.
0:16:10 > 0:16:15- Is there a connection with here? - I think there must be.
0:16:15 > 0:16:18The retaining walls have a lot of lime mortar holding the bricks in.
0:16:18 > 0:16:24The pH must be just right for the seeds to germinate and thrive.
0:16:24 > 0:16:28You can't pull that out. It's solid in the ground. How do you attack it?
0:16:28 > 0:16:30It would be a chemical treatment.
0:16:30 > 0:16:33For the small plants, we use a leaf application,
0:16:33 > 0:16:36so it's just dealing with that one plant.
0:16:36 > 0:16:40For the larger ones, our new technique is to cut the stumps
0:16:40 > 0:16:44and rather than putting a herbicide onto the stump itself,
0:16:44 > 0:16:46because you can get issues with run off,
0:16:46 > 0:16:50what we're looking at as a new system is using these plugs
0:16:50 > 0:16:56whereby you drill a hole into the stump itself, hammer it in,
0:16:56 > 0:16:58this then splits the casing
0:16:58 > 0:17:04and that herbicide dissolves directly into the sap of the tree or Buddleja
0:17:04 > 0:17:08- and gets straight into the system. - So that's very targeted.
0:17:08 > 0:17:09- That's systemic.- Yes.
0:17:09 > 0:17:14So when the chemical is released, it goes into the vascular bundle,
0:17:14 > 0:17:18which poisons the entire plant. Right to the root, nothing left.
0:17:18 > 0:17:22All being well, what it means is it's very good at killing the whole plant,
0:17:22 > 0:17:24so we don't have to come back,
0:17:24 > 0:17:26so guys don't have to go up once
0:17:26 > 0:17:30to height on the mobile platforms and it's done.
0:17:30 > 0:17:32So that is the magic bullet.
0:17:32 > 0:17:37It's the targeted application of herbicide to kill that plant.
0:17:37 > 0:17:40'Magic bullets are all well and good,
0:17:40 > 0:17:43'but we're fighting a losing battle here.
0:17:43 > 0:17:46'The Buddleja is always likely to get the upper hand
0:17:46 > 0:17:50'and it doesn't even know it's in a war.'
0:17:50 > 0:17:54The Buddleja is a plant only doing what comes totally naturally to it.
0:17:54 > 0:17:55It's a survivor.
0:17:55 > 0:18:00If we've got problems with it, maybe that's down to us.
0:18:00 > 0:18:04'Despite our best efforts, Buddleja has found a comfortable niche
0:18:04 > 0:18:07'in the overlooked spaces of our cities.
0:18:07 > 0:18:10'It's a garden escapee that has got above itself
0:18:10 > 0:18:11'and for some reason,
0:18:11 > 0:18:16'we've decided we can't tolerate it living beyond our back yards.
0:18:22 > 0:18:26'It's not just in towns that fashions have changed.
0:18:26 > 0:18:29'In one of the most remote and rural parts of Britain,
0:18:29 > 0:18:31'the Isle of Bute in Argyll,
0:18:31 > 0:18:33'another much-loved Victorian bloom
0:18:33 > 0:18:36'has been reclassified as a menace to society.
0:18:41 > 0:18:45'Scotland has thousands of square miles of forest.
0:18:45 > 0:18:49'From the millions of acres of Forestry Commission spruce
0:18:49 > 0:18:55to the ancient pines of Glen Affric, remnants of the Caledonian forest.
0:18:55 > 0:18:58'And thanks to our Victorian forefathers, a very un-Celtic plant
0:18:58 > 0:19:03'is spreading unchecked, fit to choke the glens, say its critics.
0:19:04 > 0:19:06'It's Rhododendron Ponticum
0:19:06 > 0:19:10and it's roused the ire of the Scots.
0:19:13 > 0:19:16'One of the most invasive weeds in Britain today,
0:19:16 > 0:19:20'it came from the northwest of Spain in the 1840s.'
0:19:20 > 0:19:24At the time, it was a gardener's delight with its thick, waxy leaves,
0:19:24 > 0:19:27its spreading and ground-cover habit and sprays of purple flower.
0:19:32 > 0:19:35'And it wasn't just Victorian gardeners who embraced it.
0:19:35 > 0:19:38'Rich landowners snapped it up
0:19:38 > 0:19:41'as part of their impressive botanical collections.
0:19:41 > 0:19:46'On shooting estates, Rhododendron Ponticum was introduced
0:19:46 > 0:19:49'to provide ground cover for game birds.
0:19:49 > 0:19:51'This was a fatal mistake.
0:19:52 > 0:19:55'The most common Rhododendron in Britain,
0:19:55 > 0:19:59'it spreads at the expense of almost all other species.
0:20:00 > 0:20:02'In Argyll, it can climb the ancient oaks
0:20:02 > 0:20:06'and block the light so essential for the lichen and moss.
0:20:09 > 0:20:12'Each plant produces millions of seeds.'
0:20:13 > 0:20:18Ponticum even uses chemical warfare to conquer all that surrounds it.
0:20:18 > 0:20:20It releases poison from its roots
0:20:20 > 0:20:24that knocks out anything that dares to compete.
0:20:24 > 0:20:29'The plant is host to Phytophthora, a fungus-like mould genus
0:20:29 > 0:20:32'implicated in the tree disease known as Sudden Oak Death.
0:20:35 > 0:20:37'Gordon Gray Stephens from Scottish Natural Woodland
0:20:37 > 0:20:40'knows what it's like to be at the sharp end
0:20:40 > 0:20:44'of this war against Rhododendron Ponticum in Argyll.'
0:20:44 > 0:20:47What proportion of the county is covered in Rhododendron?
0:20:47 > 0:20:50The Forestry Commission survey three years ago,
0:20:50 > 0:20:52a partial survey of Argyll,
0:20:52 > 0:20:55and they came out with over 3,000 hectares of ground
0:20:55 > 0:20:58infested with Rhododendron.
0:21:04 > 0:21:06The Rhododendron casts such a dense shade
0:21:06 > 0:21:10that the oak can't seed into that dense mat of Rhododendron.
0:21:10 > 0:21:13In 400 or 500 years' time, we won't have an oak woodland left.
0:21:13 > 0:21:17We'll just have a Ponticum thicket. In the long term, that'll happen.
0:21:17 > 0:21:20In the short term, it destroys the ground layer,
0:21:20 > 0:21:23so there's nothing left growing on the ground.
0:21:23 > 0:21:27That makes a real difference to a lot of these lower plants.
0:21:27 > 0:21:30The root can be on ground that is favourable to Ponticum
0:21:30 > 0:21:33and the layers go away into wet ground.
0:21:33 > 0:21:37Because its main root is on dry land,
0:21:37 > 0:21:41it can spread into areas it otherwise wouldn't be able to get to.
0:21:41 > 0:21:43It's like a Swiss army knife of a plant, I suppose.
0:21:43 > 0:21:47The cost of treating it is quite substantial
0:21:47 > 0:21:50so this is labour-intensive, hard work.
0:21:50 > 0:21:54The Forestry Commission reckoned it would cost £9 million
0:21:54 > 0:21:58to clear Argyll of Rhododendron in 2007.
0:21:58 > 0:22:03But the other dramatic figure is that by 2050, if we don't do anything,
0:22:03 > 0:22:08it'll cost £50 million, so the stuff is spreading so quickly,
0:22:08 > 0:22:13not doing something now means we'll have a far bigger problem later on.
0:22:15 > 0:22:19'The only way to tackle the problem effectively
0:22:19 > 0:22:22'is to gather a group of committed volunteers.'
0:22:22 > 0:22:24If we could see the last 100 years
0:22:24 > 0:22:27of Rhododendron expanding through Scotland
0:22:27 > 0:22:29it would appear as an army,
0:22:29 > 0:22:33advancing all the time up the hills, up the glens.
0:22:33 > 0:22:35It just gets bigger and bigger.
0:22:35 > 0:22:39- How would you physically attack it? - We try to get them out by the roots.
0:22:39 > 0:22:42That way, the plant is finished.
0:22:42 > 0:22:47All that might survive are seedlings coming up over the next few years.
0:22:47 > 0:22:50We knock it back as hard as we can in the first pass.
0:22:53 > 0:22:57You need a vigorous approach for a plant that is so vigorous.
0:22:59 > 0:23:03It is a bit of a battle. You need a team, really.
0:23:03 > 0:23:06One man on his own, it's a bit daunting.
0:23:06 > 0:23:10Even with two, you can go, "I'll start here, you start there."
0:23:10 > 0:23:12The more people you've got in a team,
0:23:12 > 0:23:17the bigger your army is against the army of Rhododendron.
0:23:17 > 0:23:19You engage every part of your body.
0:23:19 > 0:23:23You get battered and scratched and bruised, but it's beautiful.
0:23:23 > 0:23:26Obviously, at the end of each day you see what you've achieved.
0:23:26 > 0:23:28I like the idea that they don't go quietly.
0:23:28 > 0:23:31No, they fight back every time!
0:23:31 > 0:23:35At the end of the day, you know you've been at war for a day.
0:23:35 > 0:23:39- You know you've been fighting. - Here it comes.
0:23:43 > 0:23:46'But again, there is more than meets the eye
0:23:46 > 0:23:49'to our relationship with Rhodies.
0:23:51 > 0:23:54'Rhododendron Ponticum may once have flourished in Britain
0:23:54 > 0:23:58'before the glaciers came 20,000 years ago.
0:23:58 > 0:24:02'And maybe that's why it thrives here today.
0:24:02 > 0:24:05'It's only our decision to classify it as an alien
0:24:05 > 0:24:08'that leads us into battle against it.
0:24:10 > 0:24:13'When something is labelled alien,
0:24:13 > 0:24:17'an entire industry will spring up, dedicated to its destruction.
0:24:20 > 0:24:22'Never was that truer than with the introduction
0:24:22 > 0:24:25'of one very special foreign beauty.
0:24:28 > 0:24:32'Introduced into Britain by Philipp von Siebold,
0:24:32 > 0:24:35'a German biologist, in the early 19th century,
0:24:35 > 0:24:38'this fast-growing plant, producing big white flowers in summer,
0:24:38 > 0:24:41'quickly became a gardeners' favourite.'
0:24:43 > 0:24:47I'm here amongst the strands of Japanese Knotweed
0:24:47 > 0:24:49and it really is like a jungle in here.
0:24:49 > 0:24:52It's conquered the surrounding grounds.
0:24:52 > 0:24:56It's hard to believe this was a much sought-after ornamental,
0:24:56 > 0:24:57and an expensive one at that.
0:24:57 > 0:25:02It was very prized in Victorian gardens. You can see why.
0:25:02 > 0:25:03it's got many qualities -
0:25:03 > 0:25:08it's pollution-resistant, it grows in poor soil and it's fast-growing.
0:25:08 > 0:25:11It can put on five foot in four weeks.
0:25:11 > 0:25:14Speaking as a gardener, I can understand why they prized it.
0:25:14 > 0:25:19In fact, in 1879, the horticultural journal The Garden described it
0:25:19 > 0:25:24as one of the most beautiful herbaceous plants in civilisation.
0:25:24 > 0:25:25How reputations are lost.
0:25:27 > 0:25:32'Today it's turned into the most aggressive alien weed in Britain,
0:25:32 > 0:25:36'an outlaw we decided to hunt down without mercy.
0:25:36 > 0:25:38'True, this is no ordinary weed.
0:25:38 > 0:25:42'It out-competes everything around it.
0:25:42 > 0:25:46'The plant's complex root system or, as we gardeners call it, rhizome
0:25:46 > 0:25:49'spreads up to 20 feet in all directions,
0:25:49 > 0:25:53'as well as going down nine feet below the surface.
0:25:53 > 0:25:55'And just for good measure, the roots can swell
0:25:55 > 0:25:59'and throttle entire root systems of other species.
0:25:59 > 0:26:03'And these plants don't just grow downwards.
0:26:03 > 0:26:06'Above ground, they can grow over 20 feet a year
0:26:06 > 0:26:10'and rapidly swamp any vegetation in their path.
0:26:10 > 0:26:14'But there is a dirty little secret in our relationship with knotweed.'
0:26:16 > 0:26:18The most amazing thing about this plant
0:26:18 > 0:26:22is it's never propagated by seed. Humans spread it.
0:26:23 > 0:26:28Let me show you...the secret... of knotweed's success.
0:26:28 > 0:26:29It's this rhizome here.
0:26:29 > 0:26:33If I break a piece off and take it away, I'd spread the plant.
0:26:33 > 0:26:38'It can penetrate concrete and completely envelop a house.
0:26:39 > 0:26:43'Japanese knotweed is now posing a problem to home owners in the UK.
0:26:43 > 0:26:46'Some high street banks are refusing mortgages
0:26:46 > 0:26:49'on properties infected with the weed.
0:26:54 > 0:26:56'And removing it is difficult.
0:26:56 > 0:26:59'Not only is there the sheer mass of plant and root to remove,
0:26:59 > 0:27:04'but the soil is treated as controlled waste.
0:27:04 > 0:27:08'So a giant weed control industry has grown up along with the knotweed
0:27:08 > 0:27:11'and the two are now locked in mortal combat.
0:27:13 > 0:27:15'It's a lucrative business,
0:27:15 > 0:27:19'worth a staggering £1.5 billion per year in the UK.
0:27:20 > 0:27:23'To clear the new London Olympic site alone
0:27:23 > 0:27:26cost one contractor £9 million.
0:27:27 > 0:27:31'Clearing building land's a big part of the knotweed removal industry.
0:27:31 > 0:27:35'So what do you have to do to get rid of it?'
0:27:35 > 0:27:37You have to erect a fence to prevent humans
0:27:37 > 0:27:41from entering the area and spreading it around.
0:27:41 > 0:27:44We basically apply the herbicide to the plant.
0:27:44 > 0:27:47It can take up to three-five years
0:27:47 > 0:27:51and require several applications per year, if not more.
0:27:51 > 0:27:54The second thing is then to cut and clear
0:27:54 > 0:27:56absolutely all the surface growth.
0:27:56 > 0:27:59We then put it in a designated area and incinerate it,
0:27:59 > 0:28:02usually in a cage incinerator,
0:28:02 > 0:28:05to prevent any small fragments being dispersed
0:28:05 > 0:28:09and potentially regenerating as new infestations.
0:28:11 > 0:28:15You deal with the soil so this is classed as a toxin?
0:28:15 > 0:28:17It's classed as controlled waste
0:28:17 > 0:28:20contaminated with active Japanese knotweed rhizome.
0:28:20 > 0:28:23So if you did build on it, and you didn't get rid of it all,
0:28:23 > 0:28:28- people could have it in their front room?- Literally. That does happen.
0:28:28 > 0:28:30Getting rid of it is quite expensive?
0:28:30 > 0:28:34Yeah, there's some horrific statistics out there.
0:28:34 > 0:28:38To eradicate it all now would cost something like £2 billion.
0:28:41 > 0:28:45'The thing is, we brought all this on ourselves
0:28:45 > 0:28:48'by bringing in non-native species to an environment
0:28:48 > 0:28:51'where they could spread without natural predators.
0:28:52 > 0:28:54'The knotweed removal industry is here to stay,
0:28:54 > 0:28:57'partly thanks to government tax breaks.
0:29:01 > 0:29:04'But there is an arms race going on here
0:29:04 > 0:29:08'and we're never going to win it developing bigger, better weapons.
0:29:08 > 0:29:11'It's time to come up with a new plan.
0:29:11 > 0:29:13'One man thinks he has the answer.
0:29:16 > 0:29:19'Part of the reason Japanese knotweed flourishes in Britain
0:29:19 > 0:29:21is it has no natural enemies here.
0:29:23 > 0:29:27'But in Japan where, as you might expect, the plant is common,
0:29:27 > 0:29:29it doesn't rage out of control,
0:29:29 > 0:29:32'thanks to the insects that keep it in check.
0:29:34 > 0:29:37'10 years ago, plant scientist Dick Shaw
0:29:37 > 0:29:40'began an epic quest to find a natural way
0:29:40 > 0:29:42'of controlling knotweed in the UK.
0:29:42 > 0:29:46'His first port of call was Japan's native insects.
0:29:48 > 0:29:50'He tested various bugs that fed off the weed
0:29:50 > 0:29:55'before selecting a psyllid as the best control agent,
0:29:55 > 0:29:59'a creature with an appetite for Japanese knotweed and little else.'
0:30:00 > 0:30:05I'm really interested. How does it set about attacking the knotweed?
0:30:05 > 0:30:11It's called a psyllid. The adult female lays up to 600 eggs
0:30:11 > 0:30:13and the eggs hatch into nymphs
0:30:13 > 0:30:17and all the stages suck the sap out of the plant,
0:30:17 > 0:30:18just like a bunch of aphids.
0:30:18 > 0:30:22If you have a load of aphids, you know the damage they can cause.
0:30:22 > 0:30:26Our psyllid attacks this plant only and causes stumpier leaves,
0:30:26 > 0:30:30shorter plants and, hopefully, a less invasive species.
0:30:32 > 0:30:35'After battling suspicious authorities in Britain,
0:30:35 > 0:30:38'who quarantined his bugs for several years,
0:30:38 > 0:30:42'Dick finally got clearance last year to release them in Britain.
0:30:44 > 0:30:46'This is the first time that bio-control
0:30:46 > 0:30:50'has ever been used in Europe to fight a weed.
0:30:51 > 0:30:55'This climate-controlled greenhouse is a psyllid breeding colony,
0:30:55 > 0:30:58'where generations of the bugs are being raised to do their duty
0:30:58 > 0:31:01'by devouring our Japanese knotweed.'
0:31:04 > 0:31:09We need an awful lot of knotweed to feed them. It's mass production.
0:31:09 > 0:31:13- So this is a pantry, for all intents and purposes.- Exactly.
0:31:13 > 0:31:16A pantry with only one food source.
0:31:16 > 0:31:17Are there psyllids here now?
0:31:17 > 0:31:22Nothing on these plants. These are ready to be fed to the psyllids
0:31:22 > 0:31:25until they've got to a suitable size.
0:31:25 > 0:31:28So this is like a supermarket. I'm guessing this contraption
0:31:28 > 0:31:30is where our friends, the psyllids, are.
0:31:30 > 0:31:35This is their dining room. They feed on the plants in here,
0:31:35 > 0:31:36go through their cycle
0:31:36 > 0:31:40and we end up with more psyllids at the end than the beginning.
0:31:40 > 0:31:43This is about getting as many psyllids as possible to get them out.
0:31:43 > 0:31:46That must be an exciting moment.
0:31:46 > 0:31:48It's the culmination of a lot of work
0:31:48 > 0:31:51and an awful lot of scientists have been involved in this.
0:31:51 > 0:31:54I hope it's a triumphant return.
0:31:54 > 0:31:56What you can see here, we're lucky,
0:31:56 > 0:31:59is a couple of adults mating here, a female and male.
0:31:59 > 0:32:04There's an other interested male coming down the mid-vein.
0:32:04 > 0:32:06This is exactly what we want.
0:32:06 > 0:32:10With any luck you can see the eggs on the surface of the leaf.
0:32:10 > 0:32:13The tiny white dots are the progeny.
0:32:14 > 0:32:17There's three there, aren't there?
0:32:17 > 0:32:20'This extra psyllid seems to have turned insect reproduction
0:32:20 > 0:32:23'into an eight-legged Carry On film.'
0:32:23 > 0:32:25There's another one in there now.
0:32:25 > 0:32:30It's like a disco dance floor with one bird and three geezers.
0:32:30 > 0:32:32THEY LAUGH
0:32:32 > 0:32:34She's very popular.
0:32:34 > 0:32:38A very frustrated male charging around the leaf now
0:32:38 > 0:32:40with his bottom lip hanging out.
0:32:47 > 0:32:50'Dick's return to organic methods of dealing with weeds
0:32:50 > 0:32:53'fits with the present-day revival
0:32:53 > 0:32:57'of ancient folklore about the use of weeds in herbal remedies.
0:32:59 > 0:33:04'Today, ten million of us spend a total of £240 million
0:33:04 > 0:33:07'on herbal cures derived from weeds.'
0:33:07 > 0:33:09It looks like a big cow parsley.
0:33:09 > 0:33:11'As a medical herbalist, Dee Atkinson
0:33:11 > 0:33:16'knows a great deal about the medicinal qualities of weeds.'
0:33:17 > 0:33:19I see this as a medicine chest.
0:33:19 > 0:33:23Just looking at this, I'm excited about all the medicines I can make.
0:33:23 > 0:33:28Look at those nettles, wild garlic, all sorts of things.
0:33:28 > 0:33:32'Herbal treatment is the oldest form of medicine in the world.
0:33:32 > 0:33:37'Human use of wild plants goes back at least 70,000 years.'
0:33:37 > 0:33:39There's our friend, the nettle.
0:33:39 > 0:33:44So this Galium, or Sticky Willy we call it down south,
0:33:44 > 0:33:46you could combine those two together?
0:33:46 > 0:33:50They're really good. Nettle, cleavers and dandelion
0:33:50 > 0:33:55were the three herbs that we used as spring tonics, the idea being
0:33:55 > 0:33:57that they were some of the first herbs of the early spring
0:33:57 > 0:34:01and after a winter of preserved meats
0:34:01 > 0:34:05and no refrigeration, of course, you needed to cleanse the system.
0:34:05 > 0:34:09'It was time to turn my hand to a weed tonic.'
0:34:09 > 0:34:11I'm just going to use the leaves.
0:34:11 > 0:34:16- If I feed them in...- And I just turn the...- Just turn the handle.- OK.
0:34:16 > 0:34:20'Herbal medicine isn't just used for things like indigestion.
0:34:20 > 0:34:23'The seeds of milk thistle are the only known antidote
0:34:23 > 0:34:26'to death cap mushroom poisoning.' Some galium?
0:34:27 > 0:34:29So I'm going to get up in the morning
0:34:29 > 0:34:33and have a cup of dandelion and nettle tea to help in which way?
0:34:33 > 0:34:38- It will help with your impending arthritis...- OK!
0:34:38 > 0:34:41The cleavers are good for skin problems
0:34:41 > 0:34:43and dandelion is a fantastic bowel herb.
0:34:43 > 0:34:45A mild diuretic.
0:34:45 > 0:34:50It's used for joint problems, for arthritis and rheumatism.
0:34:50 > 0:34:53What I'm going to do is I'm going to take the dive
0:34:53 > 0:34:54and see how this tastes.
0:34:59 > 0:35:04Hoo! I can taste the nettle and I can taste the dandelion.
0:35:04 > 0:35:06It's not bad. A little bit bitter.
0:35:06 > 0:35:08It's interesting you say it's bitter.
0:35:08 > 0:35:12That's where the aperitif came from, the idea of something bitter
0:35:12 > 0:35:16- before a meal to stimulate digestion. - Interesting.
0:35:16 > 0:35:19That's perfectly easy to drink.
0:35:21 > 0:35:25'We had always known weeds could be useful.
0:35:28 > 0:35:32'But then something happened in the 1940s that made us realise
0:35:32 > 0:35:36'how unexpectedly beautiful they can be.
0:35:41 > 0:35:45'The bombing of London during the Blitz
0:35:45 > 0:35:47'had a strange side effect.
0:35:47 > 0:35:50'40,000 Londoners were killed.
0:35:50 > 0:35:53'One and a half million were left homeless
0:35:53 > 0:35:56'and 600 acres of the city were reduced to rubble.
0:36:01 > 0:36:04'But something else happened, too.
0:36:05 > 0:36:09'On May 3rd, 1945, the Times ran a front-page story
0:36:09 > 0:36:12'recording a strange consequence of the Blitz.
0:36:15 > 0:36:18'At the Savoy Chapel, just off London's Strand,
0:36:18 > 0:36:20'one of our most eminent botanists
0:36:20 > 0:36:24'used a public lecture to describe this extraordinary phenomenon.
0:36:26 > 0:36:29'The beautiful and unexpected growth of weeds
0:36:29 > 0:36:31'on London's bleak bomb sites.'
0:36:35 > 0:36:40Most bomb sites were awash with yellow and purple.
0:36:40 > 0:36:43Imagine what an incredible sight that must have been.
0:36:43 > 0:36:48This was the biggest dig over ever and the weeds wouldn't miss out.
0:36:56 > 0:37:01'Weeds' ability to regenerate and bring life where there was none
0:37:01 > 0:37:05'was not lost on the inhabitants of the ruins of London.
0:37:05 > 0:37:08'These weeds were truly welcomed.
0:37:09 > 0:37:14'One Londoner in particular was paying close attention.
0:37:21 > 0:37:25'The man who delivered the lecture was Sir Edward Salisbury,
0:37:25 > 0:37:29'a respected scientist who happened to be passionate about weeds.
0:37:29 > 0:37:31'During the Blitz,
0:37:31 > 0:37:35'he travelled to numerous bomb sites and identified a total
0:37:35 > 0:37:39'of 127 different species of weed.
0:37:39 > 0:37:43'The most common was Rosebay Willowherb.
0:37:43 > 0:37:48'Native to Britain since the glaciers, it was not very common
0:37:48 > 0:37:51'until the Blitz gave it an unexpected opportunity.
0:37:51 > 0:37:54'It spread rapidly across the bomb sites
0:37:54 > 0:37:58'as each plant produced about 80,000 seeds.
0:37:58 > 0:38:03'They also liked burnt ground and took nutrients from the ash.
0:38:03 > 0:38:06'The plant is a perfect example of how weeds bring life
0:38:06 > 0:38:10'to otherwise desolate or damaged environments.
0:38:10 > 0:38:15'They wait patiently for the right opportunity to prevail.
0:38:17 > 0:38:20'Sir Edward continued his research into weeds
0:38:20 > 0:38:22'when in 1943 he became Director
0:38:22 > 0:38:26'of the most important botanical research centre in the world -
0:38:26 > 0:38:28'Kew Gardens.
0:38:30 > 0:38:31'He wrote a book,
0:38:31 > 0:38:35'detailing his sometimes rather strange experiments with weeds.
0:38:35 > 0:38:40'It remains a touchstone for botanists to this day.'
0:38:41 > 0:38:45Sir Edward Salisbury, like most plantsmen, was eccentric.
0:38:45 > 0:38:50It wasn't enough for him to find, identify and log the plants.
0:38:50 > 0:38:54He was fascinated by the resilience and mobility of weeds,
0:38:54 > 0:38:57so he set up an experiment to find out how seeds behaved in the wind.
0:38:57 > 0:39:00'I'm going to recreate one experiment
0:39:00 > 0:39:04'to find out if the results still hold good.
0:39:04 > 0:39:08'In the test, he dropped seeds from a height of nine feet to record
0:39:08 > 0:39:12'how long they took to reach the ground in a windless environment.'
0:39:19 > 0:39:23He collected the seeds of plants he was interested in -
0:39:23 > 0:39:26Rosebay Willowherb, Buddleja and Taraxacum.
0:39:26 > 0:39:31He took a ladder and would climb up to nine feet and release them.
0:39:31 > 0:39:34The time it took to get from his hand to the floor
0:39:34 > 0:39:37would determine how easy this seed was wafted
0:39:37 > 0:39:40or spread around the city or environment it grew in.
0:39:40 > 0:39:43'The longer they took to fall to earth,
0:39:43 > 0:39:46'the further afield they could spread in the real world.'
0:39:46 > 0:39:51It's Taraxacum Officinale or the dandelion.
0:39:52 > 0:39:55Two, three, four,
0:39:55 > 0:39:57five, six. About six seconds.
0:39:59 > 0:40:03And this is Buddleja Davidii.
0:40:05 > 0:40:09It's taking about three, four seconds here.
0:40:09 > 0:40:12What's impressive about this plant
0:40:12 > 0:40:15is just the sheer numbers on the raceme.
0:40:15 > 0:40:17And this one is Oxford Ragwort.
0:40:17 > 0:40:21Finding out about plants like this really does bring out...
0:40:21 > 0:40:23the eccentric in you.
0:40:23 > 0:40:25I'm sure Sir Edward had a great time
0:40:25 > 0:40:29and I can see why, to be honest. Beautiful.
0:40:35 > 0:40:40And that is taking about 16 or 17 seconds,
0:40:40 > 0:40:43proving that Sir Edward's work...
0:40:45 > 0:40:47..was on the money, really.
0:40:52 > 0:40:54'But at the same time as Sir Edward
0:40:54 > 0:40:58'was carrying out his painstaking experiments in the 1940s
0:40:58 > 0:41:00'to put weeds on the map,
0:41:00 > 0:41:03'other scientists were hell-bent on destroying them.
0:41:05 > 0:41:08'Wartime research by the Nazis into nerve gas
0:41:08 > 0:41:10'had a peacetime spin-off.
0:41:12 > 0:41:14'The first pesticides and herbicides
0:41:14 > 0:41:19'were based directly on research into Sarin and other toxic agents.
0:41:21 > 0:41:25'Things were about to get very bad for weeds.
0:41:27 > 0:41:29'In the post-war rush
0:41:29 > 0:41:32'to maximise food production in austerity Britain,
0:41:32 > 0:41:36'weeds started being destroyed on an industrial scale.'
0:41:36 > 0:41:39Into battle against the foreign invader.
0:41:39 > 0:41:43That was the watchword of an armoured division last week...
0:41:43 > 0:41:44'As a result,
0:41:44 > 0:41:49'the weeds that had always reduced crop yields were banished.
0:41:49 > 0:41:53'Before the 1940s, useless weeds sometimes amounted
0:41:53 > 0:41:57'to a third of the total harvest in any one field.'
0:41:57 > 0:41:59As this is highly inflammable,
0:41:59 > 0:42:03two men carrying fire extinguishers are on hand through the operation.
0:42:03 > 0:42:06'Herbicides allowed wheat farming
0:42:06 > 0:42:08'to become big business for the first time.
0:42:11 > 0:42:14'And wheat turned into our leading source of vegetable protein,
0:42:14 > 0:42:18'used in everything from pasta to beer.
0:42:22 > 0:42:25'We thought we'd achieved the ultimate victory
0:42:25 > 0:42:27'in our war on weeds,
0:42:27 > 0:42:30'but the countryside has paid the price.
0:42:33 > 0:42:34'In the last 50 years,
0:42:34 > 0:42:38'Britain has lost 98% of its flower-rich meadows
0:42:38 > 0:42:42'due to production of arable crops like wheat.
0:42:45 > 0:42:49'We are only now starting to realise what we may have lost
0:42:49 > 0:42:53'when we banished weeds from our fields and created a monoculture.
0:42:54 > 0:42:58'Dr Jonathan Storkey has studied the unforeseen consequences
0:42:58 > 0:43:01'of the chemical warfare revolution.'
0:43:03 > 0:43:06What's happened since the 1950s
0:43:06 > 0:43:10is as the production of agriculture has become more intensive,
0:43:10 > 0:43:12we've used more fertilisers, herbicides
0:43:12 > 0:43:16and pesticides and also we're growing much less kinds of crops.
0:43:16 > 0:43:21We're basically growing winter wheat and winter oilseed rape.
0:43:21 > 0:43:23So we've lost the diversity
0:43:23 > 0:43:26and we're growing those crops more intensively.
0:43:26 > 0:43:31That's contracted the available niche or the habitat space
0:43:31 > 0:43:34that other species can use to grow and persist.
0:43:34 > 0:43:37So we now have quite a number of rare arable weeds
0:43:37 > 0:43:41like cornflower and corncockle that have disappeared from fields.
0:43:41 > 0:43:46And the overall amount of resource for wildlife has decreased.
0:43:46 > 0:43:50So we're losing species at all trophic levels.
0:43:50 > 0:43:53Also it's important because some of that biodiversity
0:43:53 > 0:43:56does helpful things, like pollinators,
0:43:56 > 0:44:01some of the natural enemies control the aphids in the crops.
0:44:01 > 0:44:04We need some biodiversity in the environment.
0:44:04 > 0:44:07It's not good enough to have wall-to-wall crops.
0:44:07 > 0:44:10'So without some weeds in fields,
0:44:10 > 0:44:14'we lose essential insect pollinators, as Jonathan showed me.'
0:44:14 > 0:44:16We'll look at what species were growing here.
0:44:16 > 0:44:19We've got quite a nice range of species in this quadrat.
0:44:19 > 0:44:23We recognise the dandelion. What's its role here?
0:44:23 > 0:44:26They provide pollen and nectar resources,
0:44:26 > 0:44:29particularly early in the season for pollinators.
0:44:29 > 0:44:33- So bees, very important... - Bees, butterflies, yeah.
0:44:33 > 0:44:37- We've got a Hogweed here. - Yeah, there's a couple of them.
0:44:37 > 0:44:40There's Hogweed and Cow Parsley.
0:44:40 > 0:44:43Things like hoverflies like those small, white flowers
0:44:43 > 0:44:47and they're important for controlling crop pests later in the season.
0:44:47 > 0:44:52So they go out and help clear up the insects we don't really want?
0:44:52 > 0:44:56Providing a mosaic of resources through the season.
0:44:56 > 0:44:59We want the resources here at the right time
0:44:59 > 0:45:02to encourage natural enemies later.
0:45:02 > 0:45:06So a small sacrifice for our small friends here, really.
0:45:06 > 0:45:09Yeah, we're talking maybe six metres at the edge of the field
0:45:09 > 0:45:12with reduced herbicide, reduced fertiliser
0:45:12 > 0:45:14to just provide an opportunity,
0:45:14 > 0:45:18some habitat for some of these species to persist and thrive.
0:45:22 > 0:45:24'The massive irony of this is that the very crop
0:45:24 > 0:45:28'that has become a monoculture at the expense of weeds,
0:45:28 > 0:45:31'wheat, was once a weed itself.
0:45:33 > 0:45:38'Plant scientist Prof Nick Harberd of Oxford
0:45:38 > 0:45:41'has researched the moment a weed became wheat.'
0:45:46 > 0:45:49About half a million years ago
0:45:49 > 0:45:53there was, spontaneously in the wild, nothing to do with human beings,
0:45:53 > 0:45:57a cross-pollination, if you like,
0:45:57 > 0:46:00between two wild grass species.
0:46:00 > 0:46:03So one can imagine that humans
0:46:03 > 0:46:06were cultivating this wheat in a field
0:46:06 > 0:46:10and, by chance, a weed was growing within that field
0:46:10 > 0:46:13and there was again a spontaneous hybridisation event
0:46:13 > 0:46:18between the cultivated wheat and this wild grass growing there.
0:46:18 > 0:46:22The whole process made a plant that was bigger and more vigorous.
0:46:22 > 0:46:27And as a result of that, we ended up with the wheat crop
0:46:27 > 0:46:30that we all grow and feed off today.
0:46:32 > 0:46:39'Nick can recreate exactly how wheat and weeds cross-bred in a lab today.'
0:46:39 > 0:46:40What I'm doing here
0:46:40 > 0:46:45is getting an immature flower head from cultivated wheat.
0:46:45 > 0:46:49So this is cultivated wheat. And down here next to it,
0:46:49 > 0:46:53- that is... - This is a wild wheat species.
0:46:53 > 0:46:57The idea then is to take a flower and open it
0:46:57 > 0:47:00so that you pull away these bloom cases,
0:47:00 > 0:47:04which I'm doing now. I think that's fine now.
0:47:04 > 0:47:09And now we move onto this wild flower and it's very different.
0:47:09 > 0:47:13What we're looking for now are anthers shedding pollen.
0:47:13 > 0:47:17Now that's an anther and then you come back to the flower
0:47:17 > 0:47:21where we were before and you spread the pollen
0:47:21 > 0:47:24- on the female part of the flower. - So what we've done there
0:47:24 > 0:47:28is recreated in a laboratory what happened 10-12,000 years ago
0:47:28 > 0:47:33between our domesticated wheat and our wild grass.
0:47:33 > 0:47:35They would have cross-pollinated
0:47:35 > 0:47:39- exactly the same way in natural conditions.- Exactly right, yeah.
0:47:39 > 0:47:41'Weeds helped us out millennia ago
0:47:41 > 0:47:45'and now scientists in the 21st century have turned to weeds
0:47:45 > 0:47:50'for one of the most important discoveries in plant biology ever.
0:47:50 > 0:47:54'It could save lives by creating a super wheat.
0:47:54 > 0:47:58'It all took place here at the John Innes Institute in Norwich.'
0:47:58 > 0:48:02Come on in, Chris. You need to sterilise your feet.
0:48:02 > 0:48:08- We're not bringing in anything nasty.- Viruses or anything else.
0:48:08 > 0:48:12'Dr Alison Smith is Head of Metabolic Biology here.'
0:48:12 > 0:48:17- It's the first time I've dressed up to see a weed!- We look after them!
0:48:17 > 0:48:19'Alison's team have been studying
0:48:19 > 0:48:22'a small, common weed called Thale Cress,
0:48:22 > 0:48:25'which is now used as the model
0:48:25 > 0:48:28'to map the DNA of all plants on the planet.'
0:48:28 > 0:48:34This weed is incredibly easy for us to work on. All plant scientists
0:48:34 > 0:48:37in the world take information from this weed.
0:48:37 > 0:48:39Many only work on this little weed.
0:48:39 > 0:48:42It's really useful because, like a lot of weeds,
0:48:42 > 0:48:45it goes from seed to seed really quickly,
0:48:45 > 0:48:49so we can get through lots and lots of generations,
0:48:49 > 0:48:51which makes it easy to do genetic studies,
0:48:51 > 0:48:56to understand how the weed behaves and what its genes are doing.
0:48:56 > 0:48:59About 20 years ago, plant scientists got together.
0:48:59 > 0:49:03They were working on different plants and they decided,
0:49:03 > 0:49:05"Let's work on one plant together,
0:49:05 > 0:49:09"so it becomes the model to develop our understanding of plants."
0:49:09 > 0:49:13About the same time as we were sequencing the human genome,
0:49:13 > 0:49:16we started on this little weed.
0:49:16 > 0:49:20So, in 2000, we got the entire gene sequence of this weed.
0:49:20 > 0:49:22All of the genes are known.
0:49:22 > 0:49:24At the same time as the human genome.
0:49:24 > 0:49:28So really, then, this small weed is a blueprint for all plants.
0:49:28 > 0:49:32This is the model for all plant life. That's right.
0:49:33 > 0:49:38'But the sequencing of the genome is not just for the sake of it.
0:49:38 > 0:49:41'Alison and her 600 colleagues
0:49:41 > 0:49:45'are unlocking the secrets of the plant's success,
0:49:45 > 0:49:48'like its speedy growth rate and its hardiness,
0:49:48 > 0:49:53'and transfer those abilities to the crops that matter to us, like wheat.
0:49:55 > 0:50:00'This is one of the most important discoveries in plant biology ever,
0:50:00 > 0:50:01'where one of the humblest weeds
0:50:01 > 0:50:06'could save millions of lives around the world.'
0:50:06 > 0:50:08Now we've seen our magic weed
0:50:08 > 0:50:10and you've got this genetic blueprint.
0:50:10 > 0:50:13How do you take that blueprint and apply it to arable crops?
0:50:13 > 0:50:15Well, we can start to tackle
0:50:15 > 0:50:19some of the real problems that we have with our crops,
0:50:19 > 0:50:21like disease, for example.
0:50:21 > 0:50:25Our crops are quite susceptible to some diseases.
0:50:25 > 0:50:28We've been able to breed for that.
0:50:28 > 0:50:31In Arabidopsis - Arabidopsis gets diseases as well -
0:50:31 > 0:50:34we can understand exactly how it's resistant to those diseases.
0:50:34 > 0:50:39We know what genes it needs and we can say, "Where are they in wheat?
0:50:39 > 0:50:44"Can we make sure our new wheats have the genes to resist disease?"
0:50:44 > 0:50:48Another example would be how the wheat exactly makes its seeds.
0:50:48 > 0:50:52This is the really important bit. This is human food.
0:50:52 > 0:50:57We understand a bit about the process of how these little seeds are formed,
0:50:57 > 0:51:02but in Arabidopsis, we understand it in absolute molecular detail
0:51:02 > 0:51:05and that helps us to understand how we'd make better seeds,
0:51:05 > 0:51:08bigger seeds, more nutritious seeds.
0:51:08 > 0:51:10We can apply that knowledge in wheat.
0:51:10 > 0:51:15I know scientists don't like to be too dramatic, but I'm going to be.
0:51:15 > 0:51:18Weeds could play a big role in arable crops like wheat,
0:51:18 > 0:51:21or even maybe the future of humanity.
0:51:21 > 0:51:23I think it was the starting point
0:51:23 > 0:51:27for what has to be a revolution in our crops,
0:51:27 > 0:51:29a revolution in understanding how they work
0:51:29 > 0:51:32and making them work better, and doing that fast.
0:51:32 > 0:51:38It's taken millennia to get to here. We can't afford to take millennia.
0:51:38 > 0:51:42We have to do it in tens of years or less and in order to do that
0:51:42 > 0:51:47the information from Arabidopsis has been the key to pushing us forward.
0:51:49 > 0:51:52'It's the resilience of weeds
0:51:52 > 0:51:55'and the insights they give us into helping crops survive
0:51:55 > 0:52:01'that makes them among the most useful plants on the planet.'
0:52:01 > 0:52:05Usefulness may not be just the obvious usefulness
0:52:05 > 0:52:07of, "How does it do us humans good?"
0:52:07 > 0:52:11Take some horehound to cure your cough.
0:52:11 > 0:52:14Mint tea, good for indigestion.
0:52:14 > 0:52:19It may be a much bigger ecological usefulness.
0:52:19 > 0:52:23Weeds come in to disturbed ground to try to green it up.
0:52:23 > 0:52:27So they're doing one of life's basic functions,
0:52:27 > 0:52:31to try to turn sterile, bare earth into green vegetation.
0:52:31 > 0:52:36And we should pause to think about that before we hoik them out.
0:52:36 > 0:52:41'This is nature at its most fundamental.
0:52:41 > 0:52:43'Greening over gaps is what weeds have done
0:52:43 > 0:52:46'since the beginning of time,
0:52:46 > 0:52:51'creating new life - a process called succession.
0:52:51 > 0:52:55'Here is one place where you can see this in action.
0:52:55 > 0:52:58'And no one who really observes what they do
0:52:58 > 0:53:01'can fail to be grateful to weeds.
0:53:08 > 0:53:13'Built in 1853, with money from sugar and the slave trade,
0:53:13 > 0:53:17'Poltalloch is a Victorian mansion on the west coast of Scotland.
0:53:17 > 0:53:19'The house was abandoned in 1958.
0:53:21 > 0:53:24'Since then, it's become a perfect example
0:53:24 > 0:53:28'of plants reclaiming the voids created by man.
0:53:32 > 0:53:36'These grounds would have been tended to by ten gardeners.'
0:53:38 > 0:53:39But that was a long time ago
0:53:39 > 0:53:43and now nature's moved in and nature's doing the gardening.
0:53:51 > 0:53:55'50 years ago, weeds were the brave new pioneers,
0:53:55 > 0:53:59'their rapid life cycle bringing vital nutrients
0:53:59 > 0:54:02'and organic matter to the surroundings.'
0:54:05 > 0:54:08Now these are plants whose only agenda is to set seed.
0:54:08 > 0:54:11I've got a perfect little example with this Bittercress.
0:54:11 > 0:54:14This really is a frontline weed.
0:54:14 > 0:54:16It only has one thing on its mind -
0:54:16 > 0:54:19to get its roots down, get its flower up, set its seed,
0:54:19 > 0:54:21get the next generation growing.
0:54:21 > 0:54:23But it does a very important job.
0:54:23 > 0:54:27The life cycle's so quick, it rots down, forms organic material,
0:54:27 > 0:54:29and provides a substrate of soil,
0:54:29 > 0:54:33which you can see here on this windowsill.
0:54:33 > 0:54:37This then allows other plants to move in.
0:54:39 > 0:54:43'During the first winter, perennial weeds with root systems,
0:54:43 > 0:54:46'like the bramble, would have begun to get the upper hand here,
0:54:46 > 0:54:50'their roots breaking up the ground, letting in crucial elements
0:54:50 > 0:54:53'such as oxygen and carbon dioxide.
0:54:54 > 0:55:00'The Rubus or bramble is a really aggressive coloniser.
0:55:00 > 0:55:04'The backward-sloping spikes allow it to grow over anything in its way
0:55:04 > 0:55:07'and it has a thick carpet of roots.
0:55:07 > 0:55:10'On those roots, at their apex, is a cambium cap.'
0:55:10 > 0:55:13That enables it to drill through the soil
0:55:13 > 0:55:18and in times of austerity, if attacked by a gardener's spade,
0:55:18 > 0:55:21it's these roots that enable this weed to survive.
0:55:24 > 0:55:28This plant is a very important member of the environment.
0:55:28 > 0:55:31It's clover, but it belongs to the legume family.
0:55:31 > 0:55:34On its roots there's a special bacteria called rhizobium,
0:55:34 > 0:55:37which fixes nitrogen from the atmosphere.
0:55:37 > 0:55:40All the plants around it swap this nitrogen for sugars.
0:55:40 > 0:55:44The whole process nourishes the soil.
0:55:44 > 0:55:49This plant is a highly-prized member of the process of succession.
0:55:54 > 0:55:59Down here on the floor, which was once probably a beautiful room,
0:55:59 > 0:56:00here we have bracken.
0:56:00 > 0:56:05This is a perennial that has died back over the winter
0:56:05 > 0:56:07and its leaves and debris form this lovely substrate,
0:56:07 > 0:56:09which is rich in nutrients.
0:56:09 > 0:56:12You can see this works because moss has moved in
0:56:12 > 0:56:17and, eventually, small saplings of trees start to grow.
0:56:30 > 0:56:34And, finally, the long-term species move in. The kings of nature,
0:56:34 > 0:56:36like the beech and the oak.
0:56:36 > 0:56:40This beautiful specimen is just sitting here being nursed
0:56:40 > 0:56:42by these big willows, which will die out.
0:56:42 > 0:56:46The beech will then grow up and succession is complete.
0:56:46 > 0:56:49The weeds will have done their job.
0:56:56 > 0:56:58'We've waged a war on weeds
0:56:58 > 0:57:01'because these tenacious plants have annoyed us.'
0:57:01 > 0:57:05They don't fit in with our plans to confine them within the boundaries
0:57:05 > 0:57:07of our gardens and our fields.
0:57:07 > 0:57:11Weeds don't recognise boundaries, only opportunity.
0:57:11 > 0:57:14And they are engineered to be born survivors.
0:57:24 > 0:57:28Some that were once welcomed with open arms
0:57:28 > 0:57:30are now being rebranded as alien invaders,
0:57:30 > 0:57:33and condemned to extermination.
0:57:35 > 0:57:38But our relationship with weeds will change again
0:57:38 > 0:57:42as we understand more about them.
0:57:42 > 0:57:45And the more we learn about exactly how they work,
0:57:45 > 0:57:50the more it becomes obvious how essential they are to the life cycle.
0:57:50 > 0:57:54It might pain us to admit it, but without weeds, we'd be in trouble.
0:57:54 > 0:58:00Or as Gerard Manley Hopkins put it in his 1918 poem Inversnaid,
0:58:01 > 0:58:06"What would the world be Once bereft of wet and of wildness?
0:58:06 > 0:58:10"Let them be left O let them be left, wildness and wet
0:58:10 > 0:58:13"Long live the weeds and the wilderness yet."
0:58:35 > 0:58:38Subtitles by Red Bee Media Ltd
0:58:38 > 0:58:42Email subtitling@bbc.co.uk