Environmental Engineering Reference
In-Depth Information
CHAPTER 5
BRITAIN: A NATION TIED IN KNOTWEED
Just as my fellow Britons took their favorite species with them to their imperial colonies, so they
have always brought exotics home. But after a brief honeymoon, we have turned against many of
them—especially, it seems, those go-getting, larger-than-life American species. Like some of their hu-
man counterparts, we find some of them, well, just a bit too much to handle. There are some twenty-
three hundred alien species in Britain. It is now reluctant host to American mink that escaped from fur
farms, ruddy ducks from Canada that took flight from conservationist Peter Scott's Slimbridge wetland,
and North American signal crayfish that swam free from aquaculture ponds and exterminated native
crayfish. But, as a nation of gardeners, Britons save their special wrath for an ornamental shrub from the
slopes of a Japanese volcano: Japanese knotweed. (I won't speculate on why the British and Americans,
with Japanese knotweed and kudzu respectively, have placed at the top of their hate lists weeds imported
from the same country.)
The South Wales city of Swansea is sometimes called the Japanese knotweed capital of the world.
The Japanese might disagree, but the plant (
Fallopia japonica
) has certainly made itself at home here.
In summer its jungle of bright green heart-shaped leaves and pretty white flowers covers valley sides,
chapel cemeteries, and even the sand dunes down on the beach. In winter its bare stems give the whole
city a reddish tinge. Sean Hathaway, who works for the Swansea city council, is Britain's—possibly the
world's—only full-time Japanese knotweed officer. Hathaway welcomed me at the station as one more
in the steady stream of journalists from around the world who have come to report the horror story. From
investigative titans at the
Sunday Times
and
Harper's
to essayists and bemused Japanese scribes, they
come to South Wales to walk round the “JK jungles.”
“We think the weed came to Swansea as long ago as 1918,” Hathaway told me. “We only know be-
cause we found a picture postcard of a church with a bush in the foreground. But nobody noticed it until
the 1970s, when people began to complain about this weed invading their gardens.” There was a reason
for the weed's sudden virulence. The city was for a long time the center of the world's copper industry.
But as the works shut, it became instead one of the largest areas of industrial dereliction. Knotweed
likes dereliction and has no problem with metal pollution. “It can survive in virtually any soil type,” said
Hathaway. It once flourished on lava fields, after all. It colonized land that other plants didn't fancy, and
once it got going it tended to crowd others out. The dereliction was followed by one of the biggest urban
renewal schemes in Europe. The massive volumes of earth being moved spread the knotweed rhizomes,
which have been consolidating ever since.
Japanese knotweed was a novelty even in Japan. It specialized in sending down deep rhizomes
to find nutrients beneath lava flows. It came to Europe with a Bavarian doctor named Philipp Franz
Balthasar von Siebold. Assigned to Japan by the Dutch East India Company in the 1820s, Siebold in-
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