If you were to believe everything that you read then, currently, you may be under the impression that your property is under attack by an alien plant that can grow through anything and smashes concrete, brickwork and tarmac for fun; and you might be right!
There are many horror stories around but, should you be in a panic and be unable to sleep … or is this all down to 'scaremongering' by unscrupulous contractors trying to make a quick buck?
The first samples of Japanese Knotweed were brought back from Japan by Phillipp F Von Siebold, a Dutch nurseryman, around 1845. He then sent samples to Kew Gardens where the Royal Horticultural Society sold it on to the general public. From 1850 onwards, Japanese Knotweed was planted in wetland margins and then used as a screening plant due to its rapid growth. It was then recommended for embankment stabilisation and planted as fodder for cattle.
Small fragments of the plant have the ability to produce new growth which resulted in its rapid spread beyond areas where it was first planted.
From its introduction to its rapid accidental spread, Japanese Knotweed has gone from being a prized ornamental plant to an object of complete paranoia. Recent statements by mortgage lenders have fuelled this panic by stating that they … "will not provide a mortgage on a property with Japanese Knotweed within 30 metres of a boundary".
The situation has been further confused by a lender that would provide a mortgage on a property with Japanese Knotweed, but would not lend on a property with knotweed just outside of the ownership. Whilst this may sound a little confusing, if you actually think it through then it does make sense - knotweed within a boundary can be managed and treated, knotweed outside of the boundary is 'outside' of your control.
The careful landowner should have answers for the surveyor who spots knotweed on the property. Employing a trained specialist will alleviate most problems, but well documented photographs and details of precautions taken should be kept, as well as marked and fenced areas where treatment has been undertaken.
I qualified as a Landscape Architect in the early eighties, at a time when 'wildlife' gardens were all the rage. Everyone was reducing the time spend on eradicating 'weeds' and deciding to abandon mowing regimes on their grassed areas in favour of wildflower meadows. Swathes of uncut grass abounded, with reduced areas of short mown high maintenance sward.
Japanese Knotweed was often planted as a screen or a green alternative for embankment stabilisation and Buddleja was actively encouraged to grow and planted by the hundreds to encourage butterflies. These two species are now the bane of the rail track maintenance companies and a nightmare on poorly managed sites.
This new found interest in 'natural' landscapes was seized upon by landowners as a perfect excuse to reduce their weed control budgets and save money on grass cutting costs ... with serious consequences.
What most natural landscape lovers didn't realise was that, if you stop maintaining your landscaped areas, it isn't the wildflowers that thrive, it is those plants designed to out compete our native species that will take over.
Many areas away from the watchful eye of the maintenance teams were abandoned to what were deemed wild or natural - the reality was more 'unnatural', with a massive boom in the spread of invasive species. Huge swathes of Japanese Knotweed and Himalayan balsam have spread and established to such an extent that many believe that these plants are actually native.
My personal theory is that it is down to landowners simply not looking at what has been happening. Most people are inexperienced in identifying plants and take a very simplistic view - if it's green or has flowers - then it's 'natural'. Japanese Knotweed and Himalayan Balsam are not unattractive plants during their growing period between April and October. Both have attractive flowers and lush foliage, but both will grow to the preclusion of all of our native species.
So, if we can understand why these plants have spread and why they have been allowed to gain a foothold in our landscape, should we be as fearful as the scaremongers suggest.
Well to a certain extent the answer has to be a resounding 'YES'.
We ignore these species at our peril. Negligence is these plants greatest ally, they rely on the fact that we aren't looking, they rely on sneaking up on our bits of open ground that nobody cares about - then they take over!
Open your eyes, learn to know what plants are a problem, learn to understand how these plants spread and how they expand, and learn that their only ambition is ... total domination! I believe that most people walk around with their eyes closed, oblivious to the insidious spread of the non-native species.
From a practical point of view, you need to be vocal. If you are aware that Japanese Knotweed is in your local area, don't wait until it is on your doorstep ... ring the local authority, ring the landowner - make yourself a nuisance! It's only by constant vigilance and repeated phone calls that anything will get sorted with Invasive Non Native Species. These plants will spread rapidly and can quickly dominate any area in which they get a foothold.
If Japanese Knotweed has already established itself in your vicinity, then find out who the landowner is. Knotweed has the ability to grow at a rate of roughly seven metres in all directions and will continue to expand and spread exponentially until stopped - either by some form of physical containment or by intervention from man.
Arguments will often ensue as to where the plant has originated from - thus one of the most effective precautions you can take is to plot where the plant has been spotted. Get some professional advice, or simply take a tape measure and plot the position and distance the plant is from your property. The following year, carry out the same exercise and you will quickly get an idea of how rapidly the plant is heading in your direction.
Whilst carrying out your survey, you should also be trying to find the owner of the land and advise them that if Japanese Knotweed breaches the boundary of your property you will be taking legal action and using the measurements taken over previous seasons as proof of the origin of the infestation.
With a few simple measurements and photographs, all the arguing can be sidestepped - it's a slam dunk and a legal victory - costs would be awarded for restoring your property and removing the infestation.
If you already have Japanese Knotweed within your property boundary, then the sooner you start your eradication programme the better. If you can afford to get some professional help, then this will save you a great deal of trouble - but even if you can't … then there are some simple steps that you can take.
- Fence off the infestation if you have the space - allow a minimum of three metres from surface growth to fence line (7 metres recommended)
- Allow for repeated treatment with a glyphosate based herbicide, such as Roundup or Asteroid Pro
- Repeat treatment until no new surface growth appears
- Leave the surface undisturbed for a minimum of twelve months
- Check for new growth
- Ideally, leave root system in place and plant other species around the rhizome
- Check and monitor every year thereafter
The advantage of having a professional involved is that they can bring insurance backed warranties into play and give the land owner the back up of a qualified team.
However, there should be no need to panic and no need to be scared. At the end of the day, the issues surrounding Japanese Knotweed relate more to using your common sense rather than getting into a flap about alien invaders.
New legislation has also recently come into place that states; "If an individual acts unreasonably and persists to act in a way 'detrimental' to the quality of life of those living locally, then the 'Anti-social Behaviour Crime and Policing Act 2014' can be used to either persuade or fine anybody ignoring invasive non-native species on their land".
So, yes, these plants can be a problem - but they can be dealt with - without losing sleep!
Mike Clough, Japanese Knotweed Solutions Ltd