The Daily Telegraph - Saturday - The Telegraph Magazine
A DARK FORCE
Is Japanese knotweed about to take over?
Just clearing knotweed from the 10 acres of the Olympic Park for the London Olympics in 2012, cost more than £70 million
In the mid-1800s, when Japanese knotweed was a ‘new’ exot ic species just becoming available here, gardeners were urged to consider its benefts. It was reliable, hardy and had ‘great vigour’. It was fodder for cattle (untrue), a reliable screen for the outdoor privy; its underground stems or rhizomes were an efective means of stabilising sand dunes and, especially versatile, its canes could be used to make matches. ‘A capital plant for the small town garden,’ wrote John Wood, who went on to open a nursery in Leeds.
Today, Japanese knotweed is Britain’s most dest r uct ive invasive plant, cost ing a round £166 million a year to clear and control. It cracks through roads, undermines buildings, eats up property values. It is deeply disgruntling to wildlife: insects can’t feed of it; birds rarely build nests in it. But the animal it most clearly afects is us.
Bi r mingham couple Nasreen a nd Sajid Akhtar claimed recently that they were unable to sell t heir home, a f ter a n infest at ion of Japanese knotweed in a neighbour’s garden. Despite 20 viewings with three estate agents, they could not to fnd a buyer. It was only when they tried to remortgage the terraced house – and were turned down – that they learnt the reason why. The weed was threatening the foundations of their property, meaning that no bank would lend against it. The couple were now ‘in limbo’, according to Nasreen. ‘It is putting my future and my children’s future on hold and it is totally out of control.’
‘It does seem trivial but for some people it has become a big worry,’ says Helen Jones, 60. Her husband, Bill, a butcher, 69, discovered knotweed on a piece of land he owned near their home in Stourbridge, West Midlands, earlier this year. ‘He’d had the land for 30 years and then it [knotweed] just suddenly appeared. He didn’t recognise it immediately. But then he went on the internet.
‘Bill’s biggest worry was the fnancial aspect,’ she continues. ‘That if the knotweed encroached on neighbouring land, he would be liable. Towards the end he was desperate. He thought we’d have nothing left.’ The couple had raised four children (now aged between 20 and 30) and had bought their house in the 1990s.
On February 13 this year, he went to work. Later that day, he was found at home having attempted suicide. He died the following day in hospital. It’s likely the suicide was an expression of a deeper problem. Helen says her husband had ‘ occasiona lly ’ suf fered f rom depression before. But she is convinced the precipitating event was the knotweed. ‘Bill was a very strong character. But this was something he couldn’t cope with. This was something he didn’t have an answer to. He couldn’t sleep. He could hardly eat. He just spiralled downwards.’
Japanese knotweed frst arrived in Britain in a box of 40 Chinese and Japanese plants delivered to the Royal Botanic Gardens at Kew, west London, on August 9, 1850. ‘Plant number 34’ was a simple shrub with reddish, hollow canes and heart-shaped leaves on a bowing stem.
Fallopia japonica was disseminated throughout the UK by the fashion for ‘wild’ gardens – a departure from the Victorian craze for regimented carpet bedding.
‘We ought not to forget the quick growing
ways of the great Japan Knotweeds growing fast and tall,’ wrote Gertrude Jekyll, the infuential hor t iculturalist, in a 1900 edit ion of
Home and Garden. Jekyll thought it was an excellent fanking plant for a woodland walk. And when, inevitably, the weed breached the garden walls, and began to run amok in someone else’s garden, break into someone else’s d ra i ns, quali f ic at ions bega n to creep i n. Japanese knotweed, warned William Robinson, the Victorian gardener, in 1898, ‘…springs up ever y where’. Nevertheless, it was sold as a fashionable exotic until the 1930s.
It was frst spotted growing in the wild in Maesteg, a small town in south Wales. Japanese knotweed, noted John Storrie, a curator at Cardif Museum, in The Flora of Cardif (1886), was ‘very abundant on the cinder tips’ near the town. It has since colonised just about every corner of the British Isles (with hotspots in London, Wales, Cor nwall a nd t he West Country), growing in all sorts of places plants are not supposed to grow: sandy, salty beaches; heavy asphalt; swamps and marshes.
The source of its almost supernatural resilience lies in its native habitat – it was dug up from volcanic fumeroles, outcrops of volcanic ash, near Nagasaki, where it thrived amid lava and poisonous gases owing to an extensive network of underground stems (rhizomes) that sucked up the limited nutrients available.
But in Japan it has enemies, specifcally 186 bugs and about 40 fungi. Here, it luxuriates in being predator-free. The only thing it has to do is grow, which it does, up to four inches a day in summer.
The other problem is the ease with which it spreads – not by seed, the plant is infertile. It reproduces by regenerat ing it s rhizomes, which creep out horizontally deep underground, and sends up shoots. And even a tiny bit of rhizome ( just 0.7g, the size of a fngernail) can generate a new infestation.
‘We are a small island with a lot of people and we move soil around a lot – to build roads, develop brownfeld sites – and that is how it spreads,’ points out Dr Richard Shaw, regional coordinator for invasive species, at the Centre for Ag r icult ura l Bioscience Inter nat iona l (Cabi), an intergovernmental research organisat ion. ‘ The main i s sue i s red i st r ibut ion through human intervention.
‘It’s defnitely spreading and the spread is exponential,’ he continues. It is also a problem across Europe a nd America, but is more extreme in Britain.
The potential cost of trying to eradicate the plant in Britain has been estimated at more than £1.25 billion ( just clearing it from the 10 acres of the Olympic Park for the London Olympics in 2012, cost more than £70 million). Last year, George Eustice, an environment minister, said there were ‘no plans to attempt a national eradication’ because of the cost.
‘Our strateg y is really focused on trying to stop the next Japanese knotweed from getting into the country and from spreading,’ says Olaf Booy, technical coordinator of the Non-Native Species Secretariat, a team based within the Animal and Plant Health Agency, which works on beha lf of t he Gover nment. ‘ But t he Government is investing in a bio-control agent [more about this later] and has been helping to f und loc a l g roups t hat a re dea li ng wit h Japa nese k not weed,’ he adds. Def ra (t he Department for Environment, Food & Rural Afairs) spent £1.5 million on such groups from 2011 to 2015. It is currently employing a Local Act ion Groups coordinator to assist wit h funding bids.
There are two methods of killing knotweed: poison (it can take fve years of repeated applications, costs around £2,000, and shoots can still rise from a plant you thought you’d killed years earlier); and digging it out completely. This means excavating to a depth of at least two metres and taking the resulting ear th to a specially desig nated landfll. The remaining soil may have to be lined with a heavy-duty plastic membrane. This can cost upwards of £10,000, even for a domestic property.
A source of excitement in recent years has been biological control – using natural enemies to keep knotweed in check. The key was to fnd an insect that only fed on knotweed and didn’t attack any of the UK’s native plant species. Dr Shaw and his team at Cabi tested nine insects and whittled it down to one – the psyllid. Releases have been made a nnually since 2010. But the bug, a sap-sucker, has not adjusted well to the UK. ‘It has got all the characteristics of a successful agent: it lasts a long time; it produces hundreds of eggs; but it’s not taking of and we don’t know why,’ Shaw explains. ‘It might be because it’s been 140 years under a Japa nese summer a nd t hen it’s suddenly thrown out in Berkshire in the spring.’ The plan is to collect new stock from Japan. ‘Quite often these things lose their mojo when they’re in the lab,’ he says. Shaw is also investigating a second control agent: a leaf-spot fungus.
In the meantime, knotweed professionals worry about an impending cataclysm that will result in unimaginable amounts of knotweed, possibly in our own lifetime.
Fallopia japonica (a female plant) has already cross-bred with her cousin, the less intrusive giant knotweed. ‘You can get all sorts of hybrids back-crossing with Japanese knotweed and the danger is that we will eventually end up with male Japanese knotweed,’ explains Brian Taylor, who runs The Knotweed Company, a f ir m specialising in knotweed eradicat ion, based in Daventr y, Northamptonshire. The weed’s seeds, which are currently bar ren, would, efectively, be switched on.
Taylor goes on to present compelling evidence of knotweed’s g rowing immunity to herbicides, which is another worr y. Taylor is interest ing to listen to, if unbelievably alarming. ‘If we’re to get evolution and resistance, what could we do?’ he asks. ‘We are l iter a l ly just l ook i ng at exc avat ion a s a control measure.’
I meet Sean Hathaway, an ag ile, f leecewearing man, in mid-August – when the knotweed is starting to produce frilly, white blossomy fowers. ‘One of its few benefts – if it has any – is bees love it,’ he says. Hathaway works for Swansea council and is known locally as the ‘knotweed ofcer’, owing to his 20-year battle with the plant.
Swansea, Wales’s second city, has for decades now been beset by knotweed. Its histor y of
It was dug up from volcanic fumeroles, outcrops of volcanic ash, near Nagasaki, where it thrived amid lava and poisonous gases
copper mining and processing, combined with widespread redevelopment in the 1960s and 1970s, when derelict factories were turned into enter prise parks and shopping cent res, is, Hathaway suspects, behind the apparently unstoppable infestation. Ofcially, Swansea has around 250 acres of knotweed. But the last survey was done back in 1998.
He describes the battle against knotweed as ‘stable’. Every year he poisons a few thousand square metres, every year it takes hold elsewhere. He takes me on a tour of knotweed sites. This includes a very considerable hillside, rising from the site of an old quarry, not far from the city centre, which is so uniformly green it’s hard to tell from a distance what is knotweed and what is not. Close-up I realise it is all knotweed. ‘It’s choked everything else,’ he says, explaining the harm that would have come to the shrubs and grasses. ‘It is impressive,’ admits Hathaway, who, like many who make a liv ing killing or studying Fallopia
japonica, is simultaneously horrifed and awed by its power.
The council received it s f irst knotweed complaint in 1970. But since 2012, mortgage lenders have started rejecting loans outright if knotweed is found on a property (even an infestation on a neighbouring proper ty can be enough to put them of).
Liz Wakeman, a project manager f rom Bristol, had a great-aunt who lived in Swansea. ‘She was bedridden with quite severe dementia and about 18 months ago, it got to the stage where we had no option but to get her into a nursing home. So we decided to sell her house to raise money for her care,’ she explains. The estate agent went to value the property.
‘He called me,’ Wakeman recalls, ‘and said, “You’ve got a massive problem.”’
After enlightening her about the knotweed, the estate agent estimated the value of the house – not £100,000 or so, as Wakeman had anticipated, but £45,000.
‘Unfortunately, I don’t think people understand the impact not only on property prices but also on what it’s doing to their property. When we got Environet [a frm specialising in the eradication of Japanese knotweed] to do the frst treatment and they cut it back, we saw the extent of the damage: there was a wall at the bottom of my great-aunt’s garden and the knotweed had literally pulled it over.’
After treatment (costing £10,000) the house sold for £73,000. Wakeman’s great-aunt died while the sale was going through. ‘Some of the neighbours have got it up to their back door and they don’t seem to care,’ she says.
Half a mile away, on Llang yfelach Road, is Caersalem Newydd Baptist Chapel. Denise Rees, 75, has been a member of the church si nce she was a ch i ld a nd she s wea r s knotweed has been in the churchyard for as long. ‘As children we used to go up there, cut of a piece and use the tube as a pea-shooter,’ she says. ‘Many years ago, when we had more members, the youngsters used to go up and try to clear it. But they never got rid of it. And now it’s just got worse and worse.’
The knotweed is so advanced it has smashed up gravestones and tipped them over, like a violent intruder. For the past two years, the congregation of 40 has funded a professional knotweed killer out of the collection money. But the cost – £700 so far – only covers the lower end of work. ‘My parents are buried right at the top and my grandmother’s grave is next door,’ says Rees. ‘We try to keep it clear, so we can visit. My husband sprays it with Roundup [the systemic herbicide], but it’s awful.’
Thirty or so miles north-east of Swansea is the valley town of Merthyr Tydfl, once a centre of iron production and now one of the 10 most deprived areas in Wales. Mark Sawyer works for Merthyr Valley Homes, the social-housing company, and is responsible for 4,200 houses and fats in the area.
He’d been receiving knotweed complaints for some years, but, initially, placed the blame on the tenants. ‘When a tenant says, “I’ve got weeds in my garden,” you tend to think, well cut them back then. Or look after your garden, because we don’t provide that service. We do roofs, kitchens, bathrooms.
‘And the tenants would say, “Well I have been cutting it back.” Some would go a bit further a nd put a bit of diesel on it. They’d say, “Whatever I do, it just comes back.”’
Three years ago, he decided to investigate. ‘Some of the infestations had reached the point where the tenants were unable to enjoy their gardens,’ he reveals. One garden was twothirds knotweed.
In 2013, Saw yer decided he needed to spearhead what he describes as a ‘strateg ic approach’ a nd ask his board for f unding. I wonder how difcult it was to get money for what some might say is just a weed. ‘They’d gone beyond that. They know it’s the dark force,’ he replies.
He asked for £90,000 and got £15,000 a year, for a fve-year programme of repeated applications of herbicide in 25 properties.
‘What worries me is we’re just tinkering at t he marg ins,’ he ad mit s. ‘ Knot weed will develop. We’ve seen how it spreads and it’s very aggressive. We don’t have the budget to deal with the entire estate. We are treating 25 properties. Next year I know there will be 35, and the year after there will be 45. We can probably add 10 ever y year. It’s almost like tr ying to resist gravity. It has taken over the valleys.
‘It’s almost like trying to resist gravity. It’s not a battle we are ever going to win. Meanwhile I am just watching this vast army advance towards us’
It’s not a battle that we are ever going to win.
‘In the quiet hours of the morning when I can’t sleep and I think of all the roofs leaking, all the central heating I need to put in, I’m now thinking about knotweed and how we have got properties that back on to councilowned land and private land. We are trying to do our bit, but unless every landowner is prepared to do theirs, it’s no good. And we have very little control over private landowners, and a lmost no working relat ionship wit h t he council because t hey say t hey a re almost skint. Meanwhile I am just watching this vast army advance towards us.’
In 1823, Philip Franz von Siebold, a Bavarian doctor and et hnolog ist, was appointed doctor-in-residence for a community of Dutch traders based in Dejima, a man-made island in the harbour of Nagasaki, in Japan. At this time Japan was a closed countr y with wide-ranging restrictions on the activities of foreig ners (for ex a mple, lea r ning to read and write Japanese was against the law). But Siebold’s medical skill won him inf luential contacts and he was granted unprecedented access to the country. For the next fve years, Siebold, with a commercial objective, secretly collected specimens (plants, animals, objects).
On September 18, 1828, as he prepared to sail for Europe with 89 crates of illicit goods, a storm forced the ship ag round. Siebold hid t he precious specimens in false-bottomed fower boxes. The ship sailed but Siebold was det a ined, inter rogated a nd later banished from Japan for life.
He moved to Antwerp, in Belgium, and then to the Netherlands, where he tracked down his scattered collection. In 1842, he opened a nursery in Leiden and began to market his collection of ‘exotic’ plants across Europe. And so it was that in 1850 he sent an unsolicited package to Kew Gardens.
At the time of Siebold’s death in 1866, his nurser y boasted 1,000 diferent species and varieties of plants. When FW Burbidge and P Barr, two well-known English horticulturalists, visited the nursery in 1883, they found a neglected jungle, overrun by just one plant: Japanese knotweed.