Japanese Knotweed Although it would be untrue to claim expertise, I can certainly consider myself to be intimately familiar with Fallopia japonica (Polygonum cuspidatum). When we first came to North Glen more than forty years ago, my gardening mentor Jock Smith saw it in the patch I intended to resurrect as a vegetable garden and said, Thon polygonomll take some getting rid of, and he was right. I went to see Hugh McKenzie and he said, what you want is SBK brushwood killer. Thatll do it. A glance at the label revealed the stuff to be what my countrymen had sprayed liberally along the Ho Chi Minh Trail - Agent Orange. I sprayed it liberally on the polygonum, and it was like a dose of hallucinogen - the stalks all wilted and collapsed and re-growth came up crazily twisted and soon died - result! Two weeks later new shoots appeared and shot skyward, reaching the original six and seven feet and seemingly as vigorous as before. So I hacked it all down, dug out at least a tonne of roots, poured some diesel on the heap and set fire to it. It didnt want to burn well, not being dry enough, and several more applications of diesel were required before I was satisfied there was no life left in it. I got on with growing vegetables and pulling up the polygonum shoots as they emerged. They can grow more than a foot in a few days, but I managed a decade or so with the stuff relatively suppressed. Then my attention was diverted from the vegetables for a few years by matters of making a living and suchlike, and the knotweed was soon back in control of half the garden. When I returned to the vegetable patch, it was seven feet tall and impenetrable, so I dug out another couple of tonnes of roots, let them dry out and burned them. That was a dozen years or more ago, and even though it gets pulled up every time a wee shoot appears, I still see a few shoots every season. Some show evidence of roots surviving a meter down. Its under control, but still alive after forty years of persecution, and Ive no doubt that if we turned our back on it for a few years it would once again own half or more of the garden and be sending roots onward! This is a plant worthy of respect! Wikipedia says, It is a frequent colonizer of temperate riparian ecosystems, roadsides and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species I reckon most of these colonies are the result of folk digging it out of their gardens and, erm, tipping it in said waste places Taliesin has just such a colony which were attempting to control by non-chemical means. Digging it out isnt really a practical possibility, so were hoping to control it through a combination of shade and pure physical abuse. Weve transplanted beech seedlings into the patch, the taller the better (7 to 9 feet) to enable them to put on leaf and grow canopy above the knotweed. Ive observed that it doesnt readily spread into shady areas (e.g. beech canopy) and also that even though they dont cast deep shade, birch trees appear to have some sort of repellant capacity, so we have put some birch in the mix. And, of course, we offer Knotweed Corner as a therapeutic opportunity for anyone who wants to expunge aggression or anger by taking a stiff walking stick and having a bash...I recommend it. Make sure you clean your boots before leaving the site, though, as a new plant can grow from less than one gram of root material. 8|
Posted on: Sun, 10 Aug 2014 15:45:45 +0000
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