Friday, 17 August 2012

Invasive Species - Know the enemy Part 1


I had the opportunity to go along and speak to the Bo’ness Community Council last week on the topic of Invasive Species and community projects to eradicate, or at least control their spread. Whilst I’m sure I bored them to tears with my diatribe, what came out was that lot of people need to be able to recognise these alien invaders. I will start with two species of Invasive plant , Japanese Knotweed and Himalyan Balsam

So rather than do yet another rant and rave about invasive species, here is a pictorial guide as to what the most common non natives look like, with a few basic facts about the species

With reference to getting previously unknown stands of Japanese knotweed, Himalyan Balsam and other invasive non-native species logged by the council please follow the link below.


This takes you to the Falkirk Council Ranger Service page. Look to the right hand side of the page, under “Forms” and click on the link “Report sightings of Invasive Species". Your report will assist the council to map the various species shown in this entry. Alternatively leave your siting here as a comment against this post.

Japanese Knotweed



Above - a close up of the distinctive JKW leaf

The Facts – Japanese Knotweed or JKW is a fast growing non-native from Japan, originally introduced to the UK by Victorian plant collectors (As so many of these were). It produces copious shoots and root systems and reproduces vegetatively, ie any part or fragment of the plant can produce a new plant, which quickly grows into an ever expanding stand. The stands of upright shoots are clustered so tightly that nothing else can grow in it’s midst, except for trees that were there before the infestation. As nothing eats it areas where it is present are effectively dead to wildlife.

Spread – the most common initial incursions are caused by flytipping of the cut plants. It famously spreads down water courses and infest the banks. The Stand spreads laterally from the centre by invading new teritory each year with it's roots and sending up new shoots. The plant can colinise up to three metres a year in any direction that the roots can grow into.


The photograph above shows new stems growing more thinly around the edges of the main stand - Next year this will be densly poulated with stems and the process will repeat yet further into the woodland.



Looking into the stand of JKW from it's edge (above) you can see that no light penetrates to allow other plants to germinate or photosynthesize. Indigenous plant life is there for kicked out of any area where it has gained a foothold


Treatment – Whilst JKW can be dug out it is a major job – the roots go down 3 metres and extend the same from the edge of the stand. Any soil contaminated must, under law be landfilled in special waste cells or buried 5+ meters deep, either way being prohibitively expensive. It can be effectively treated with herbicides, but garden strength sprays will not finally kill the plants roots and can make it difficult to treat properly I in future years. DO NOT attempt to pull out the stems or dig out the roots, as this will simply spread the infestation more quickly.


Inside the stand, it's dark, crowded and virtually nothing else grow due to a lack of light, nutrients and water. The above picture was taken on a bright, sunny day in August.

Himalyan Balsam


The Facts - Another asian invasive this time coming from the foothills of the Himalya mountains in India. An annual plant, it produces flashy pink and purple flowers that compete with native wildflowers for pollination, and then give way to large explosive seedheads. Once dry the seed head will burst open at the slightest touch and eject seeds up to 7 metres away. As each plant can distribute up to 800 seeds that remain viable for 2 years, the plant is classified as highly invasive. It is often mistaken for JKW because it has tall fast growing upright shoots clutered in fairly dense stands. Whilst other plants can survive  in balsm stands initially, over years the HB competes strongly for pollination, water and nutrients with indigenous plants. This process weakens the ecology of any hbitat Himalyan Balsam appears in by decreasing it’s biodiversity. Less indigenous seeds from Scottish wild plants means fewer seed eating bird, mammal and in following years fewer of the wild plants themselves.


Himalyan Balsam at Hall Glen

Treatment – As an annual plant HB has a shallow root system, relying entirely on the spread of viable seeds each year for the continuation of it’s species. Thus the plant can simply be pulled up at any point before it sets seed. The plant can also be eradicated by spraying.

Close up of the flowering heads and seed pods



Competition for pollinators from Balsam affects british wild plants. Populations of many  pollinating species are also in decline due to habitat destruction and agricultual chemical usage

Thanks for reading this blog entry. If you spot either of the above species featured here, please use the link above to get them logged and mapped by the Falkirk Council Ranger Service. Alternatively leave a comment against this post stating which species you have seen and where, giving  an OS grid reference, or a good description of its location.

To mount your own campaign against invasive species contact Falkirk Environment Trust about biodiversity grants. You must be part of a Falkirk Area based, constituted community group or charity, and have a bank account in the name of that group.



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