This is Japanese Knotweed (Fallopia Japonica).  This particular patch has quadrupled in size in the past ten years, so assuming it continues at the same rate of growth, in another ten years it will have arrived at the boundary of our land.

I might ramble on about the brambles, but they are nothing compared to this botanical thug.  This alien does not creep towards us by the cover of the undergrowth, it just stamps right over it. 

Japanese Knotweed is infamous for being able to grow up through concrete and can propagate itself from the tiniest piece of root.  Fortunately it does not spread by seed in the UK, our Victorian forbears thankfully only imported female plants.  There is a good chance that every single plant in the UK is a clone of one original female plant.

I can well understand why it was introduced to Britain.  As far as ornamental garden plants go it’s just my thing, lots of fresh, green foliage.  I don’t find it unattractive, even in Winter the stems have a pleasing wiggly structure.  Nevertheless, it poses a threat to our native plant species (and native insect species dependent upon them) and smothers all other growth in its path.   Japanese Knotweed is an enemy of bio-diversity.

In its native Japan, knotweed rarely assumes the growth and stature is does in this country as it is kept in check by pests and fungal disease.  Eradication in the UK is a tricky problem.  Great care must be taken when using herbicides near waterways and indeed any where else.  Currently tests are underway to introduce biological controls.  Biological controls need to be selected carefully on the basis that they thrive solely upon the invasive alien plant, and should not pose a threat to any of our native plant species.  It takes time to establish what will work safely but I am hoping a green option for control of knotweed is not too distant. 

Here is a forbidding list of don’ts for Japanese Knotweed!:

• Don’t delay, control and eradicate knotweed as soon as it is spotted. It will only get harder to remove as it grows larger.
• Don’t try to dig it up as this will only lead to an increase in stem density.
• Don’t contaminate council composting schemes with knotweed waste.
• Don’t fly-tip knotweed waste.  (Or while I’m at it anything else!)
• Don’t attempt to chip knotweed or compost it on your pile. It can be composted separately on thick plastic sheeting, only when you are certain it is dead, can it be spread.
• Don’t move it around – always dispose of on site where found.
• Knotweed is considered to be ‘controlled waste’ always obtain approval from relevant authorities before disposing of it.
• Don’t be careless with herbicides.  Follow instructions carefully and only spray on still, windless and dry days.  Obtain approval from Environment Agency if near a waterway.

As our climate changes and we experience warmer winters it is likely that many potentially invasive plants previously killed off by the cold will survive.  It is important now that people become aware of the devastating effects of invasive species.  Increasingly we need to learn how to recognise the space invaders and prevent their spread. 

Here are some other space invaders to look out for; himalayan balsam (Impatiens glandulifera), false acacia (Robinia Pseudoacacia), Montbretia (crocosmia x crocosmiflora), fairy fern (Azolla filiculoides) and Rhododendron Ponticum.  Some of these are still available in garden centres, be aware of them and don’t let them escape the garden wall.  To find out more visit  www.nonnativespecies.org. 

This is Himalayan Balsam growing around the car park at our local pub, a ten to fifteen minute walk downstream (now you know why we never get anything done!)  It is unlikely to spread via the water up to us, but people find it very pretty and do pick it and even purposely propagate it.  It shades out native growth and so does need eradicating, this is thankfully a bit easier than getting rid of knotweed and conservation groups often have a blitz on it.  Until next time, sleep well, hope you don’t have any extra-terrestrial nightmares!