Sandy’s Garden ... Japanese Knotweed Again

Sandy Simpson
Sandy Simpson

While we were cruising in the eastern Mediterranean recently, we were privileged to enjoy a copy of The Times every day.

The newspaper was downloaded from the internet and then printed on board on a very large number of sheets of A3 paper. We normally read a Scottish daily newspaper while we are at home … and so miss out on many primarily English stories … and the time spent reading The Times meant that we majored on English news items and missed out on most predominantly Scottish stories. And one of the articles which caught my eye was headed, “Get your knotweed under control or face £2,500 fine.”

Let’s begin with a reminder of what Japanese knotweed is. The Environment Agency … a Westminster government service … has this to say. “Japanese knotweed is a tall, vigorous, ornamental plant that escaped from cultivation in the late nineteenth century to become an aggressive invader in the urban and rural environment. It is a rhizomatous (produces underground stems) perennial plant with distinctive, branching, hollow, bamboo-like stems, covered in purple speckles, often reaching 2-3 m high. The leaves of the mature plant are up to 120 mm in length with a flattened base and pointed tip and are arranged on arching stems in a zig-zag pattern. The plant flowers late in the season … August to October …with small creamy-white flowers hanging in clusters from the leaf axils (point at which the leaf joins with the stem). The underground rhizomes are thick and woody with a knotty appearance and when broken reveal a bright orange-coloured centre. The rhizome system may extend to, and beyond, a depth of at least 2m and extend 7m laterally from a parent plant. During winter, the leaves die back to reveal orange/brown coloured woody stems which may stay erect for several years. Stem and leaf material decomposes slowly, leaving a deep layer of plant litter. During March to April, the plant sends up new shoots, red/purple in colour with rolled back leaves. These shoots grow rapidly due to stored nutrients in the extensive rhizome system. Growth rates of up to 40 mm a day have been recorded.”

I could not have written a better description than that! So far, so good; Japanese knotweed is a large, deep-rooted, robust, ornamental plant. But knotweed regenerates easily and spreads far and wide, even small fragments of roots or stems … which have been dispersed along watercourses, by transfer to waste recycling facilities, by fly-tipping, and by agricultural or industrial development … readily forming new plants. It particularly likes sites such as road verges, railway land, watercourse corridors, waste ground, cemeteries and any heavily disturbed ground. It then disrupts sight lines on roads and railways and disrupts flood defence structures. The plant damages the urban environment by pushing up through tarmac and paving, out-competing other species in planting programmes as part of landscaping schemes and causing aesthetic problems as litter accumulates in the dense thickets formed by the plant. This also encourages vermin. It is not a nice plant at all! And now the Home Office has introduced new legislation in England to allow the issue of what are called ‘community protection notices’ requiring gardeners to clear knotweed off their land if it is seen as posing a problem and making any refusal to comply with such an order a criminal offence.

Here in Scotland, the Scottish Environment Protection Agency (SEPA), in its Technical Guidance Note on the on-site management of Japanese knotweed, currently promises that you will not be prosecuted for having Japanese knotweed growing on your land, although you can be issued with a management order if you live close to, or threaten the interests of, a Site of Special Scientific Interest (SSSI). Still, I’d watch this space!