Walking the banks of the Water of Leith in spring time shows how diverse Edinburgh’s flora and fauna can be. Due to the river running through a variety of habitats ranging from farmland to a built-up city centre, it is no surprise that such a huge range of species can be found in close proximity to the capital’s main watercourse.
As a weed control company specialising in eradication of invasive non-native species, our main focus around the Water of Leith is Japanese knotweed (Fallopia japonica). Other invasives are present in abundance: Giant Hogweed (Hercaleum mantegazzianum); Himalayan Balsam (Impatiens glandulifera) and Buddleia (Buddleia davidii).
Japanese knotweed is a hardy perennial that can quickly colonise riparian areas. Its prevalence beside watercourses is well documented and it is a nationwide problem. Over the past 3 years, the Rivers and Fisheries Trust Scotland (RAFTS) have led a control programme on many of Scotland’s major waterways in order to reduce the impact of Japanese knotweed and other non-native plants. Hopefully this control programme will be rolled out in the capital in order to safeguard Edinburgh’s native species and to protect the city’s properties from this alien invader.
So what damage is Japanese knotweed causing to the Water of Leith and Edinburgh?
Some of the damage is immediately obvious and some less so. Due to the Japanese knotweed’s ability to increase in height by nearly 10cm per day during the spring and summer months, it can quickly tower over smaller, native species. As a result it will reduce the amount of light that reaches the native flora as well as restricting the native plants’ water and nutrient supplies. This ‘out-competing’ of native species leads to a reduction in biodiversity. This may not be immediately obvious to passersby, however, over time it will lead to a loss of native plant species and therefore a reduction in insects and animals that rely upon the native plants for their existence.
Perhaps the most obvious damage caused by Japanese knotweed is the disturbance or breaking of ground covering, e.g. the emergence of Japanese knotweed through paving. Generally, this happens when Japanese knotweed is growing beside a hard surface such as brick paving and the plant creeps beneath the brickwork. New shoots find their way up through gaps in the surface and eventually, as the plant matures, the brickwork becomes dislodged or damaged. This usually leads to some misinformation being passed around by any witnesses and it perpetuates the myth that Japanese knotweed will grow through concrete regardless of the thickness of the structure. Like many plants, Japanese knotweed will find the path of least resistance and work its way through small gaps or weak areas. It is not unusual for Japanese knotweed to emerge through tarmac as the surface is somewhat porous and therefore easily breached.
So if you are out for a stroll along the Water of Leith then keep your eyes peeled for Japanese knotweed and stay clear of it. It can be easily spread through disturbance of the rhizomes (underground creeping stems) or by cuttings of the plant’s stems. More information on Japanese knotweed can be found here.
If you suspect that you have Japanese knotweed at your property in Edinburgh, contact us here or call 0131 441 2953.
IWA. Getting to the root of the problem.