How Well Do You Know Your Knotweed?

Last week we tweeted about a picture of Japanese knotweed (Fallopia japonica). The fact we tweeted about Japanese knotweed isn’t a particularly amazing or wildly interesting thing to be honest - many companies specialising in knotweed survey and control are tweeting pictures of knotweed at this time of year. However, our picture was different… The reason it was different was by virtue of the fact that it actually showed two species of knotweed found in the UK - Japanese knotweed and it’s less common cousin, Himalayan knotweed (Persicaria wallichii).

Oddly enough, it wasn’t the picture itself that put the proverbial ‘cat amongst the pigeons’. Instead, it was the title of the tweet not matching the subject of the picture, or so you would have thought based on a quick glance! But that was the reason for the tweet... to show how easy it can be to miss evidence of this highly invasive and destructive species - particularly when it's growing in-between other plants, especially species of the same family (as show in the accompanying picture).

The law on non-native species, which includes Japanese knotweed, is still governed by Section 14 of the Wildlife and Countryside Act 1981 (as amended). However, the Wildlife and Natural Environment (Scotland) Act, which came into force in 2011, made significant amendments to the law on non-native species in Scotland. Under the legislation, it is an offence to deliberately or unintentionally allow a plant to grow in the wild at a place outwith its native range and/or otherwise cause a plant to grow in the wild at a place outwith its native range.

As implied by the above legislation, the presence of Japanese knotweed should not be taken lightly, and to this end Scottish Natural Heritage has published detailed guidance to help landowners understand the legal implications associated with knotweed and other invasive, non-native plant and animal species. The advice, which is published on their website, also includes help on control, disposal and available funding. In addition, a Code of Practice on Non-Native Species was published in 2012 by the Scottish Government.

Graham Sennhauser (TETRIX Ecology's Principal Ecologist) has written a Knotweed Factsheet to help facilitate the identification of Japanese, Giant, hybrid and Himalayan knotweed, which can be freely downloaded from our web site.

Identification sheets for other invasive non-native species can be downloaded from the GB Non-Native Species Secretariat.