Japanese Knotweed has been a guest on our shores for around two hundred years, initially as a desirable ornamental but more recently as a much maligned and virulent intruder. Here, Ian Graham, Managing Director of Complete Weed Control, a specialist contractor, talks about the truth of the large, herbaceous perennial plant.
In recent years a flourishing industry has appeared, to rid concerned clients of the problems brought by its presence. The growth of this industry has been almost as spectacular as the spread of the species itself throughout the UK, with some areas having remarkable populations of the plant.
For the customer however, there are many different takes on what is the best course of action, when to do it and how much it should cost. The need to deal with Japanese Knotweed is dictated by the circumstances in which it is found to be growing, a construction project for example with a very short window of opportunity may well require a more direct approach than, let’s say a stand of knotweed growing on a roadside verge.
The law though is clear, as a landowner you have a responsibility to prevent its spread into the wild, (Countryside and Wildlife Act, 1981, section 14.2). The interpretation of this law though is less than clear, whilst the disturbance and distribution of soil containing rhizome is evidently an issue, does allowing the growth to remain unchecked constitute a crime?
For the client, the critical issue is to establish the facts regarding Japanese Knotweed. In many respects the required knowledge is not that complex or indeed elusive, even a moderate understanding is sufficient to seek out a suitable solution to any given problem. Of course there are many ‘specialists’ whose sales pitch is riddled with tales of crumbling new builds and it is their desire to maintain the illusion that only massive spending can result in control.
In searching for a contractor to resolve your problems, you will hear of unique ‘systems’ to produce control with herbicides within tiny timescales, single application methods that are a permanent fix, rhizome testing that confirms
results and no doubt many other weird, wonderful and inevitably expensive solutions.
The truth however is that all contractors have access to the same limited number of active ingredients within their choice of herbicide. These herbicides are controlled by law and are detailed within the UK Pesticide Guide and fully within the CRD website.
The labels for these products detail their suitability and need to be adhered to fully. Equally the application itself needs to be carried by an operator with the correct training and certification who will need regular update training to ensure full legal compliance. There are only a handful of these herbicides available on the market and some of them will be out of the question due to the proximity of trees, other desirable vegetation or indeed the presence of a water course.
That means that there are no ‘cure all’ concoctions available to any contractor. Equally, there are very few methods of application. Spraying, injection, wiping etc all have their place, but sadly none provide instant success. The testing of rhizome is great but its results mean very little, knowing that part of the plant is ‘dead’ is really no help. Digging up every last part of the extensive rhizome system and testing it would be useful; however, surely it rather defeats the point? In essence, unless every part of the plant is successfully treated (especially the non-visible element), removed, or isolated by means of barrier materials, then the problem is not solved.
Happily, this is usually entirely possible without breaking the bank. Careful consideration of the site, its history, the planned development, level changes, timescales, buried services; previous attempts at control (or concealment) are all to be considered. Sometimes minor modifications to a planned build can create the opportunity to resolve matters with ease.
The document of choice to learn about what might be appropriate in terms of an approach to control would be the EA guidelines. Both comprehensive and well illustrated it is a great starting point in learning about the subject. Sadly even this is also somewhat flawed. A great example being the instruction to excavate seven metres from the edge of a stand of knotweed, but only 2.5 metres down.
When excavating, it is practically unheard of for rhizome to venture this far from the surface vegetation, however it is common for the rhizome to be three metres deep. Arguably the most important advice within the guidelines can be found in the section entitled ‘The status and use of this code’ where the following observation is made, ‘Site managers need to be careful of claims made about products and methods on offer for controlling Japanese Knotweed, particularly those that claim it can quickly destroy the problem completely’. Wise words indeed.
There are only really three options when it comes to controlling Japanese Knotweed, the first to remove it from the site in its entirety, the second to treat with herbicides, or thirdly to isolate it from the structure which it threatens.
Each of these options has their place, but rarely is the best solution immediately apparent whilst there are so many factors that will influence the choice.
There are a number of simple rules that ought to be remembered and passed on within the industry, they are as follows:
– Always survey a site for Japanese knotweed first.
– Never initiate site clearance prior to being certain about the presence of the weed (a little knotweed goes a very long way).
– In the event of Japanese knotweed being identified, isolate it. Not doing so has cost some companies large sums of money.
– Take the time to consider all of the available options before embarking upon what could be a very expensive and fruitless exercise.
On a final note, don’t forget that we are dealing with a weed here, not radioactive waste or a killer virus. A quick search of the internet will reveal numerous tasty sounding recipes with Japanese knotweed as the key ingredient.
For the most part, a considered programme of control with sufficient thought as to how best to manage any impact upon the intended development plan will bring a happy and sensibly priced conclusion to the problem.
For more information on how to deal with ragwort or any other form of weed control, please contact Complete Weed Control on 01325 324 277or visit www.completeweedcontrol.co.uk
