Britain fights back against its most notorious plant invader.
The Victorians brought Japanese knotweed to Britain as an ornamental garden plant, but they underestimated how vigorous it is. Alan Titchmarsh fights his way through dense Japanese knotweed in a graveyard in Swansea. It is the fastest-growing plant in Britain so, despite dying back in winter, it will be back in the spring when it can grow by as much as an inch a day. By the summer it can be 10 feet tall and completely smothering anything that tries to grow below it. This is why Swansea has appointed Britain's first knotweed-control team, battling with machetes and powerful weed-killers. But the problem is that knotweed grows through underground runners and a new plant can grow from a mere fragment of one of those runners. Not even concrete can stop it. It has been estimated that to eliminate it entirely would cost over a billion pounds. Luckily, our particular strain can not produce seeds so there is a limit to how fast it can spread. But if a mutation or hybrid created fertile plants, then Britain would be smothered in it.