Japanese Knotweed

It's horrendous - don't even think of giving a cutting to your favourite aunt unless she wants some concrete broken up or her new tarmac drive punctured - it's also illegal to do so. Railway cuttings, school grounds and the banks of waterways seem to be the favourite haunts of this pernicious weed [deliberately introduced to the UK by enthusiastic Victorian plant-hunters]. Find this on any 'public' ground and - if you are the good citizen - you report it as you should to the Environment Department, the good men in hiz-viz jackets, wielding clipboards and GPS, will descend upon you and slap the most stringent legal requirements on you to 'safely' dispose of this weed. Think 30 tonne lorries, huge diggers, and miles of cartage to a prepared site in middle-England where the offending plant - roots, shoots and all - will be buried 30 meters beneath a suffocating layer of lifeless subsoil..........and still it may survive given a small earthquake or some ill-informed site re-development. Oh, it is rather pretty in flower though!

The generally accepted way to deal with this weed is by liberal application of that favourite weedkiller 'glyphosate' or 'Roundup' to give it its commercial name. But even this otherwise effective [and safe] pesticide has limited success with JKW. The strength of this plant lies in its roots - kill the top-growth and the roots may shrivel but they still persist and will eventually sprout new growth. Yes, there are some old fashioned remedies that would kill the roots as well but we can't use these toxins in the modern world. And timing is also critical in the application of any pesticide to JKW - hit it just before it flowers and control is much better. But given the vast acres of this stuff it is difficult - expensive - to have the stuff watched everyday through the flowering season just waiting for the one day to spray. And if it rains on that day?

But there is now another way to deal with this beast and I welcome the introduction of a new friendly bug from Japan that feeds on JKW. It's never going to completely eradicate this weed - it would destroy its own food source if it did, but hopefully it should reduce it to tolerable levels where other plants can re-establish. The scientists behind this introduction don't promise complete control and see the bug as a parallel aid to all the other control methods [mechanical and chemical] that are used. This is especially important on the banks of waterways where JKW has completed swamped some areas and reduced the local habitats to virtual monocultures of JKW with other plants and wildlife forced out entirely.

The introduction of new and foreign species into old environments is always a bit of a gamble though [think rabbits in Australia] - so lets hope this tiny Japanese bug doesn't get bored with JKW and decide on a new and friendly plant for lunch! Our scientists have promised as much.