Thursday, March 18, 2010


A recent news item confirms what has been in the pipeline for some time, that a bug, of Japanese origin is about to be released in carefully-selected sites in the UK, to control Japanese knotweed. A friend in Japan tells me it has been collected in her area, Kumamoto, right on the southern tip of Kyushu. Here’s a local newspaper story:
Given the disasterous history of introducing predators of pests (like Australias’ cane-toad problem) some have expressed alarm at introducing the insect. This does sound like it has been thoroughly researched though, apparently for several years, to ensure that the bug doesn’t affect native flora - so let’s stop worrying and get on with it.
Knotweed is a magnificent plant, which is why the Victorians introduced it - William Robinson in The Wild Garden suggests planting in ‘the pleasure ground’ and by the waterside. Maybe we should blame him? Call it ‘Robinson’s knotweed’ instead of blaming the Japanese.
The press of course love Japanese knotweed. They love stories about foreign exotics causing trouble generally. Something about the triffid nature of the story appeals to that elemental need for journalists to frighten people. And of course an excuse for a bit of subliminal racism - have you noticed that the country origin of these scare-plants or pathogens is always emphasized: Spanish bluebells, Dutch elm disease etc. By the way, if you ever see buddleia being called ‘Chinese buddleia’ then you can be sure that someone has decided its a bad thing and is to added to the list of proscribed plants.
Japanese knotweed is undeniably a huge problem in a few areas, and an irritant in many more. It is not going to take over the country any more than the entire population is going to be eating raw fish for breakfast, or even spreading miso on toast like I do. There is an unattractive eco-fascist tendency which tends to see all non-native plants as problems waiting to happen, and the knotweed as simply the tip of an iceburg. Some ecologists however have pointed out that some spring wildflowers like wood anemones are able to co-exist happily with knotweed and others that growing alongside rivers it is very good otter habitat.
The spread of knotweed since its introduction in the latter 19th century is of course a warning to all in horticulture, that we do need to be responsible with what we grow and where we plant it, but the reality is that the problems we have with invasive aliens is pretty minimal compared to those faced in many other countries. Our long growing season which enables our aggressive grass flora to make vigorous growth for most of the year sees off most potential invaders. And some others, like buddleia, are a positive benefit.
I’d be quite happy to see knotweed as yet another part of our flora, kept well in check by the little Kumamoto-bugs or whatever they are called, just popping up now and again by the waterside, just like William Robinson would have intended.


Rob (ourfrenchgarden) said...

Give me knotweed anytime over those 'homeboys', horsetail!

Now they're a nightmare to get rid of.

Dave said...

I've been struggling to come to a intellectually satisfactory position on invasive aliens since I started gardening in Alberta. One thing that I find useful to keep in mind is that 9-10,000 years ago, nothing was 'native' here but a couple of kilometers of glaciers. Everything here is a relatively recent alien invader. I imagine that the same applies to where you live - unless you had rather large refugia.

Anne Donald said...

I agree that knotweed is an attractive plant. However, its spread in this area is very obvious. We have a network of cycle paths round here and it is dotted along these, bits having been knocked off by cyclists and transported further up. Also, it is very much in evidence in practically every lay-by up the West Coast (Scotland) for the same reasons. I don't object to the plant itself, but it seems VERY dominant and seems to wipe out all the native flora in its wake. Mind you, what would the West Coast be without 'wild' rhododendron?