The UK is under attack from Japanese Knotweed… or is it?

Mike Clough unravels the truth about this invasive plant

If you were to believe everything you read, then you may be under the impression that your block could be under attack from Japanese knotweed - an alien plant that can grow through anything and smashes concrete for fun. 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 Japanese Knotweed plants in the UK were brought back from Japan by a Dutch gardener called Phillipp F Von Siebold around 1845. He sent samples to Kew Gardens where the Royal Horticultural Society sold it on to the general public. From 1850 onwards it 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 Japanese Knotweed have the ability to produce new growth, which resulted in its rapid spread beyond areas where it was first planted.

In the early 1980s 'wildlife' gardens were all the rage. Everyone was reducing time spent on eradicating weeds and mowing regimes at larger residential developments were abandoned in favour of 'wildflower meadows'. Swathes of uncut grass abounded with reduced areas of short mown high maintenance grass. This new found interest in 'natural' landscapes was seized upon by landlords and freeholders as a perfect excuse to reduce their weed control budgets and save money on grass cutting costs….with serious consequences.

Many areas away from the watchful eye of maintenance contractors were abandoned to what were deemed 'wild' or 'natural' plants but the reality was more unnatural with a massive boom in the spread of invasive species. What most natural landscape lovers didn't realise was that if you stop maintaining your landscaped areas, it isn't the wild flowers but those plants that can out-compete our native species that will thrive – often to the exclusion of everything else. Huge swathes of Japanese Knotweed and Himalayan Balsam have spread and established to such an extent that many now believe that these plants are native.

Be afraid…

Both these species have attractive flowers and lush foliage so although both will grow to the preclusion of our native species, should we be as fearful of them as the scaremongers suggest? The answer to this question 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 bits of open ground that nobody cares about – then they take over! Most people walk around with their eyes closed, oblivious to the insidious spread of non-native species of plants. So open your eyes, learn which plants are a problem, learn to understand how they spread – and learn that their only ambition is… total domination!

Make yourself a nuisance

So, from a practical point of view what can flat owners do? First, you need to be vocal. If you are aware that Japanese Knotweed is in your local area, don't wait till it's on your doorstep. Ring the local authority; find out who the landowner is; ring the landlord or freeholder - make yourself a nuisance! It's only by constant vigilance and repeated phone calls that anything will happen. These plants will spread rapidly and can quickly dominate any area in which they get a foothold. 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 communal gardens. 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.

While 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 should be awarded for restoring your property and removing the infestation.

Dealing with the problem

If you already have Japanese Knotweed within your block's boundary, then the sooner you start an eradication programme the better. If your service charge will cover the cost of getting some professional help then this will save you a great deal of trouble – but even if you can't afford this 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
  • Repeat treatment until no new surface growth appears
  • Leave the surface undisturbed for a minimum of 12 months
  • Check for new growth
  • Ideally leave root system in place and plant other species around the stem
  • Check and monitor every year thereafter.

If you are selling your flat, one of the main requirements for a potential buyer will be to see a planned and detailed Knotweed eradication strategy. If your property manager or RMC follows the points outlined above and photographs the works, there should be no reason for there to be problems. The advantage of having a professional involved is that they can bring insurance backed warranties into play and give the buyer's lenders the back up of a qualified team.

Don't panic!

There is no need to panic and no need to be scared. The issues surrounding Japanese Knotweed relate more to using your common sense than getting into a flap about alien invaders.

However, if an individual acts unreasonably and persists to act in a way that could be considered 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.

These plants can be a problem – but they can be dealt with without losing sleep and, hopefully, without falling out with your neighbours!

What do mortgage lenders say?

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 the panic over Japanese Knotweed 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 one 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.

While 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 a boundary is outside your control.

The hard facts of issues relating to mortgages are that in these harsh economic times, if a lender has any reason to withhold money then they will, so what should you do? The careful homeowner should have answers for the surveyor who spots knotweed on their property. Showing that your property manager or RMC is employing a trained specialist to deal with the problem will satisfy most lenders but a detailed report prepared using advice and information available on the internet should also be sufficient to push a sale through. Well documented photographs and details of the precautions taken should be kept, as well as marking and fencing areas where treatment has been undertaken. If a detailed programme of works has been commissioned and careful track kept relating to areas of growth, then there is no reason for a lender to withhold money on a mortgage.

Mike Clough
Japanese Knotweed Solutions Ltd
T: 0161 723 2000
E: mike.clough@sltd.