Fight against invasive knotweed: Vienna goes on the offensive!

Fight against invasive knotweed: Vienna goes on the offensive!

Japanese knotweed has spread widely along the Liesingbach in Vienna and is causing headaches for the responsible authorities. MA 45, which is responsible for local waters, has already taken measures to curb this invasive plant. But combating it is extremely difficult, especially due to the plant's high regenerative capacity and the special challenges associated with its spread. My district reports that MA 45 is informed about the affected areas and regularly removes plants by hand, as chemical treatments are excluded for nature conservation reasons.

The topic has been on the agenda at least since District Councilor Stephan Steinbach from Neos asked during a district council meeting. Japanese knotweed, whose roots lie deep underground and spread through subterranean runners, was introduced to Europe in the 19th century as an ornamental plant from East Asia. Today it is showing its invasive potential in full bloom and displacing native species, creating monocultures that endanger biodiversity. NABU explains, that the plant can grow up to 30 cm per day during the main growing season and that parts above ground die off in autumn, which increases the risk of erosion of the topsoil.

The challenges of combating it

What measures are necessary to get Japanese knotweed under control? It requires intensive and regular mowing – at least 6 times a year, every 3 to 4 weeks. It should be noted that the clippings do not have to be composted, but rather burned professionally to prevent them from spreading again. The fight is not only time-consuming and costly, but also requires the cooperation of authorities and private individuals, who are asked to completely tear out the plants and dispose of the clippings appropriately.

There are around 900 invasive species in Germany, including many plants such as knotweed, which corresponds to around 1% of the total established species there. The Federal Agency for Nature Conservation shows that there is also an increasing trend in neobiota species, which has increased particularly strongly in the last 170 years. This is related to global trade and mobility, which favor the presence of these plants. Colder winters limit their occurrence, but climate change could reduce this barrier in the future.

The situation surrounding Japanese knotweed is tense and requires rapid action. It is our responsibility to protect our native plant species and maintain biological diversity in Vienna. The use of the MA 45 is an important step in the right direction, but the support of the population is also essential in order to effectively combat this invasive species.