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Can Surrey gardeners be blamed for knotweed invasion?
By Heather Driscoll-Woodford
BBC Surrey

Japanese Knotweed

Japanese knotweed has been labelled as an "aggressive superweed" - a title the mobile shrubs in John Wyndham's novel the Triffids, would be proud of.

But the three-legged, venom flinging plants would have been no match for new weed on the block, Fallopia japonica.

For the knotweed is one of the most invasive plants in Britain, causing millions of pounds of damage each year.

And despite planned trials using sap eating bugs, experts are still at odds on how to destroy the leafy menace.

Just like the plot of Wyndham's book, the Government are stepping in to fight the green troublemaker, by sending in an army.

But unlike the book, the army in question is made up of Psyllids, which are tiny sap-eating Japanese insects.

SEND IN THE PSYLLIDS
The Psyllid sucks the sap out of the Knotweed, makes the roots weaker and kills it eventually
Scientists are confident the bugs will not harm native species
The insects will initially be released on a handful of sites

Wildlife Minister Huw Irranca-Davies is quoted as saying: "These tiny insects, which naturally prey on Japanese knotweed, will help free local authorities and industry from the huge cost of treating and killing this devastating plant."

And Dr Dick Shaw, lead researcher with Cabi - a not-for-profit agricultural research organisation in Surrey is hopeful this is the solution to the problem too.

He told BBC Surrey "The Psyllids are being released in isolated sites and if successful this will be increased."

But not everyone is convinced that the small hungry bugs are a match for the herbaceous marauder.

Psyllid
The tiny but possibly effective Psyllid army is on the march

Some mortgage lenders will refuse loans on property that is affected by knotweed and arguments can ensue over who is responsible for the eradication of the plant on private land.

Nic Seal, an expert witness in Japanese knotweed disputes, from Cobham based Environet, says "If you have Japanese knotweed on your land you need to act fast to eradicate it."

"The bug could provide an effective low cost control method but is highly unlikely to result in complete eradication. In situations such as development sites and gardens, eradication must be the ultimate objective to prevent damage to property, disputes and litigation."

He thinks the use of Psyllids will take far too long to be effective.

Blame the Victorians

Japanese knotweed was introduced to the UK by the Victorians in the mid 1800s.

The Royal Botanic Gardens at Kew have a record of receiving a plant specimen, sent unsolicited by a keen botanist overseas, on 9 August 1850. However there is no evidence to show that it was passed on.

Japanese knotweed
Did Surrey's Victorian gardeners start the knotweed invasion?

But the earliest record of a nurseryman selling the plant was in 1854, when neighbouring Kingston nurserymen Messrs Jackson and Son started trading in it.

And the knotweed was cropping up elsewhere around the country too.

Initially, it was welcomed as an ornamental garden plant. And with its bright green leaves and tall creamy white spikes of delicate flowers you can see why.

Surrey's famous garden designer Gertrude Jekyll even recommended the planting of a dwarf version in some of her designs, although she later rescinded, saying it should be "planted with caution."

In fact, it was much admired for at least a decade, even winning a gold medal at a society of agriculture and horticulture show, before anyone realised that not everything in the garden was coming up roses.

WHY SHOULD WE CARE?
Knotweed can grow three feet in one month
It can can regenerate itself from a piece the size of your fingernail
It can grow through solid concrete
It displaces other plants and can spread without seeds!

The once welcome oriental guest had quietly got its feet firmly under the table, was stealing the covers at night and was hogging the bathroom too.

Just like a distant relative who has outstayed their welcome, but far more difficult to get rid of.

In his 1907 book The English Flower Garden, author John Murray. wrote that "Polygonum cuspidatum" as knotweed was then called, was "easier to plant than to get rid of in the garden".

With Japanese knotweed it wasn't just a case of packing its bags and wishing it bon voyage. It had moved in for good.

And 100 years later it's still here, helping itself to our back gardens, parks and byways.

But if the Psyllids are hungry enough, maybe not for much longer.




SEE ALSO
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Garden invaders: Japanese knotweed
16 Sep 08 |  Science & Environment
Can an insect control knotweed?
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Superweed's astonishing growth
08 Mar 10 |  Science & Environment

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