Japanese knotweed invasion – Could it ever happen again…?

Author: Mike Clough

Date Posted: Wednesday 14th June 2017

When we look back on some of the mistakes with plants that our forebears have made, it’s easy to think that we would never have been as blind to the problems that have been caused. I have often repeated the phrase …’the Victorian gardeners are responsible for many of the problem plants that we have today…’

The gardeners of this period were just beginning to explore the world and to bring back samples of new plants from wherever they travelled. The designers were masters of the universe and felt that plants could be manipulated to suit their designs – there was no fear of what damage could be caused or the longer-term implications on bio-diversity or loss of native species – this just wasn’t on their agenda.

Japanese knotweed, Himalayan balsam and Giant hogweed – all imported and planted by the Victorians for either flower (balsam) drama (hogweed) or even rapidity of growth (JK).

It was once said of famous landscape gardener William Kent – ‘he leapt the fence and saw that all nature was a garden’. The original use of the quote was to show how the designer had incorporated the surrounding landscape into his designs. With use of the ‘ha-ha’ (basically a ditch which prevented cattle from walking into the garden) Kent made landscaped flow from manicured lawn into field and the countryside beyond in a seamless fashion without the use of fence or wall to delineate the boundary.

The phrase has always amused me as it was about this time that many invasive non-native species must have been thinking to themselves… ‘let’s leap the fence and treat all of nature as our garden’…. which is exactly what they did…

Exploding seed heads and huge florets producing thousands of seeds ensured that these Victorian imports were never going to stay confined to the spaces that the gardeners of the day prescribed for them.

It was only ever going to be a matter of time before these plants became a problem.

One of the aspects of these type of invasions that never really gets talked about is …’death’…I’m not talking about ‘death’ of the plants but the death of the gardener that first introduced the plant. If you have a rapidly growing wetland plant introduced by a garden designer – the plant is used to give the scheme some instant maturity. All well and good if the gardener lives long enough to then control the growth of this plant after the establishment phase has been achieved.

BUT….what happens if the garden designer dies and doesn’t have somebody taking over the management of the scheme. Maybe nobody is aware of the invasive nature of the nurse plant used to create some depth to the planting – and does nothing to prevent it becoming rampant…??

I think this is something that we need to be aware of in our current climate.

Only recently on Gardeners World – Monty Don showed us American Skunk cabbage and highlighted the problem the plant can cause. He visited a garden where the plant had run amok and the owner was waging a mini war against new growth…. but what happens if this guy dies.

Sorry I know I’m being morbid – but seriously the guy has a massive plot of land. The plot of land borders onto a major watercourse and the plot is full of American skunk cabbage. The invasive plant will dominate over our native flora and spread rapidly using systems modified to help it grow in its native location- which applied to our UK environment – give it a massive advantage over our native plants.

Do we really think that if this guy gets ill or has an accident …. his first priority will be …must make sure the skunk cabbage is dealt with …

NO – ain’t going to happen.

He might …if he’s lucky …sort his will, he might sort out who will inherit his house, car, watch collection and his premium bonds…. but he is not going to write into his deeds that the skunk cabbage must be dealt with???

People all over the UK are in a mighty battle with Japanese knotweed – they might be 1/2 or maybe 3 years into an epic 5/10-year battle with some major knotweed growth. Some of these may well work for local authorities or large land owners…but…again…what happens if they get ill or die or simply move jobs??

Invasive plants have time on their hands.

These plants can pretty much live forever whilst we puny humans have a very limited time on earth.

I also strongly believe that the impetus to manage and control our invasive non-native species may well flounder when the current crop of enthusiasts retire or simply pass away?

Will there be another Mike Clough waiting in the wings? Will Trevor Renals daughter take over from him as spokesman for our native plants…?? Is Dick Shaw in the process of cloning himself to ensure that the various bio-control strategies put in place are continued to a point where they are successful???

So…in answer to the question – Japanese knotweed invasion – could it ever happen again? unfortunately it probably is happening right now, probably not too far from where you live ….

…it’s just that nobody has noticed …yet.

Mike C

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Mike Clough

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