Environmental Engineering Reference
In-Depth Information
dulged his love of plants, often taking them as payment for surgical procedures. He shipped his favorites
home, where they were planted in his employer's botanical gardens, in Leiden.
Samples reached Britain's equivalent, Kew Gardens, sometime in the 1850s, and they were widely
sold to commercial nurseries.
1
Rather like kudzu in the United States, its Japanese origins initially made
it an attractive novelty. The celebrity gardener of the day, William Robinson, was a fan. An Irishman,
Robinson was famous for rebelling against the military monocultures of flowerbeds of the time. He
wanted a cacophony of bright expansive plants growing together in a less tidy and more natural way.
His “wild gardens” teemed with exotics gathered from across the globe. He brought goldenrod and as-
ters from North America, for instance. He liked lilies and pampas grass and Japanese anemones. In his
most famous topic,
The English Flower Garden
, which was first published in 1870 and afterward con-
stantly updated with his new finds, Robinson called Japanese knotweed “a plant of sterling merit . . .
undoubtedly one of the finest herbaceous plants in cultivation.”
2
Several of Robinson's “wild plants” showed their wildness by growing rather too well. When they
proved too much and were thrown away, there were predictable results. A plant like Japanese knotweed
could thrive almost anywhere it found space and sunlight. It took to waste dumps, railway embankments,
and graveyards across the land. It was growing wild in London by 1900 and across Yorkshire by the
1940s. By the 1960s, it had settled onto the barren moorlands of the Scottish Hebrides.
3
As it traveled,
its reputation changed from Honshu darling to Oriental scourge of the land. Today most gardeners would
agree with the Royal Horticultural Society that it is “a pernicious pest.” TV news stations revel in stories
of how it bursts through the foundations of houses, poking into living rooms and spreading like some
malign houseplant. News reports often include interviews with scientists wearing lab coats and masks
to explain how nasty it is.
4
But how much of a scourge is it? Does it pose an economic threat? And how
widely has it spread in the British countryside?
The British government's Environment Agency calls JK “indisputably the UK's most aggressive,
destructive and invasive plant.”
5
It “shad[es] native plants and damag[es] hard structures such as tarmac,
paved areas and flood defence structures” and is classified alongside the most toxic chemicals as a “con-
British economy a staggering $250 million a year—or a pint of beer for every person in the land—but I
can find no evidence that anyone spends even a small fraction of that amount on fighting Japanese knot-
weed. The Environment Agency, the country's largest land manager, spends around $3 million a year
killing and uprooting it. Swansea's council spends less than $50,000 on it a year. It turns out the cost is
an estimate from CABI, a former government agency that is now a nonprofit consultancy and invasive
species eradicator. Dick Shaw, its deputy director—and often the lab-coated scientist in those TV news
scare stories—told me it was an extrapolation from data collected in Swansea.
7
The calculation goes like this. Swansea, as a recognized hot spot for the weed, is the only place in
Britain to require building developers to certify that there is no knotweed on land before they get plan-
ning permission for building on it. So if they have any JK, they have to exterminate it. Swansea says
that just under 3 percent of its planning applications necessitate treatment. The typical treatment cost
is around $8,000. There are on average 568,000 planning applications for building across Britain each
year. But here is the bit I find impossible to accept. CABI decided to assume that the national rate of in-
festation would be similar to that in Swansea, at 2.25 percent. On that basis it reckoned that nationwide
12,800 applications would need treatment. It then doubled the treatment cost to allow for legal costs and
other extras and multiplied to produce a national cost of Japanese knotweed of just under $220 million
a year. Or almost $250 million, to allow for expenditure by public bodies on riverbanks, roadsides, and
railway embankments and potentially lowered property values.
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