Japanese knotweed Fallopia japonica tops the table of alien, introduced plants that have become invasive weeds in Britain. Its phenomenal capacity to spread via deep, tough underground rhizomes and its resistance to herbicides, coupled with its tendencies to undermine building foundations, footpaths and roads, have created thriving businesses that specialise in trying to keep it under control. Introducing the plant into the wild is an offence and although it's not illegal to cultivate it in a garden, disposing of it when it begins to overwhelm your plot is a major problem, as Japanese knotweed-contaminated soil is classified as controlled waste and has to be removed by specialist companies. In the past much of the spread of the plant has probably been due to gardeners dumping plant waste, beside roads, rivers and canals. The fact that mortgage lenders are now refusing to lend to buyers of houses with Japanese knotweed in their garden should be sufficient deterrent for anyone contemplating planting it in their plot.
Since our Victorian ancestors first introduced it into their landscaped gardens it has spread around the country via fragments of rhizome in soil, especially in urban waste ground where it often forms four metre tall forests. Apparently, 137,500 tonnes of contaminated soil had to be removed from the London Olympics site alone, before construction could begin and, nationwide, about £150 million is spent every year trying to control Japanese knotweed. One ray of hope for those seeking to bring it under biological control is that trials of a plant psyllid bug called Aphalara itadori, recently approved for release into infested areas, indicate that this insect could weaken the plant and make other forms of control, like herbicides, more effective
So, with all its destructive tendencies, is there anything positive to say about this aggressive invader? Well - excuse me while I reach for my flak jacket - there is. It's a magnet for honeybees. This fine specimen, that I photographed last weekend growing beside a pavement in Newcastle, near the Ouseburn, was humming with them. It's an ill wind, etc., etc.................
Posts
