The town of Bocholt is trialling a new method to combat invasive plant species

- The town of Bocholt is taking active steps to combat the spread of invasive plant species and is launching a targeted control programme on a test site near the Ostring. As part of an inter-municipal LEADER project, efforts are being made there to control Sakhalin knotweed using a combined method of repeated cutting and soil replacement. The project will run until 2028 and is intended to provide practical insights for sustainable nature conservation.

Two invasive knotweed species are becoming increasingly widespread in the Bocholt urban area. The most common of these is the so-called Japanese knotweed (Phalopia japonica), whilst the Sakhalin knotweed (Fallopia sachalinensis) is somewhat less common. Both species are very vigorous and can reach a height of up to three to four metres in the summer months, forming dense monocultures that displace native flora. As the above-ground parts die back in winter, they leave behind bare patches, which increases the risk of soil erosion, particularly near water bodies. A key problem in controlling them is the deep-reaching root runners, known as rhizomes, as new plants can emerge from even the smallest root fragments. Spread usually occurs via these rhizomes, for example through contaminated soil or compost.

For the pilot project, the city has selected an area of around 650 square metres near the Ostring, right next to the dog walking area. A specialist contractor began on Monday by first cutting back the dense stand of Sakhalin knotweed completely. The topsoil was then dug out to a depth of about ten centimetres to remove the roots directly from the topsoil. After sowing a grass seed mixture, the test area will be mowed weekly. This ongoing mowing prevents the formation of foliage and new shoots. This leads to the plant's long-term weakening, as it cannot carry out photosynthesis and therefore cannot produce energy for growth. The aim is to test a practical and sustainable method so that the area can later be used again for planting native trees and shrubs.

"Due to its extreme regenerative capacity, Sakhalin knotweed poses a major challenge for municipal nature conservation", explains Caroline Bücher from the Urban Greenery and Environment Department at the City of Bocholt, who is overseeing the project together with her colleague Rainer Ebbing, "using a combined method of soil replacement and keeping the shoots permanently short, we aim to systematically weaken the plant and prepare the area for native trees and shrubs in the long term."

The measure is part of a supra-regional project under the LEADER Bocholter Aa scheme, in which the municipalities of Isselburg, Bocholt, Borken, Rhede and Velen are participating. Each of the participating municipalities is tackling a different invasive plant using different methods. Whilst Isselburg is tackling the late-flowering cherry and Borken is combating ragwort, Rhede is focusing on giant hogweed and glandular impatiens, which is also the focus in Velen. Through this inter-municipal approach, various strategies are being tested and evaluated in parallel.

"Invasive plant species do not stop at city limits", says Bücher, highlighting the importance of inter-municipal cooperation, "Through close cooperation within the LEADER network, we are pooling our resources in the Westmünsterland region, testing different approaches in parallel and thus jointly developing ecologically and economically sound solutions for the entire region."

The citizens of Bocholt can also make an important contribution to preventing the further spread of the plant within the urban area. If the plant is first found in one's own garden, individual plants or small stands should be dug up at an early stage, taking as much of the root mass as possible. Small quantities of plant parts should not be placed in the home compost or in the organic waste bin, but should be disposed of with general waste. For larger quantities or in case of uncertainty, it is advisable to consult the Bocholt Waste Management and Services Company (ESB) in advance.