Invasive neophytes are non-native plant species that have arrived in Europe with direct or indirect human assistance and have successfully established themselves here. Some of these species, such as Himalayan balsam, Japanese knotweed, Canadian goldenrod, and giant goldenrod, are spreading unchecked in the Styrian Enns Valley and forming large, dominant stands. Non-native plant species can cause enormous economic, ecological, and health damage.
Regulation (EU) No 1143/2014 of the European Parliament and of the Council on the prevention and management of the introduction and spread of invasive alien species obliges Member States to implement its provisions at the national level. This list includes all invasive plant and animal species that have either not yet reached Europe (prevention) or that are already causing problems in Member States, requiring appropriate management. The currently applicable list includes, among others, Himalayan balsam, and corresponding management measures are currently being developed.
Himalayan balsam (Impatiens glandulifera) was introduced from the Himalayas in the 19th century as an ornamental plant. Its first recorded presence was in 1889 at the Weidlingbach stream (Lower Austria). This annual, light-loving plant exhibits remarkable vigor and spreads rapidly near wet meadows and bodies of water. Its shallow root system, which dies back in autumn, increases the risk of erosion along waterways. Each plant can produce approximately 2,500 seeds, which are dispersed by a catapult mechanism. The seeds remain viable for up to seven years and are primarily spread via water (buoyant seeds) but also through soil, garden waste, and tools. Due to the seeds' long viability, long-term control measures are necessary.
Once introduced (e.g., as a privacy hedge or ornamental plant) or unintentionally brought onto your property via construction equipment or excavated material, Japanese knotweed (Fallopia japonica) is extremely difficult to control. Therefore, the disposal of contaminated soil during land reclamation should be seriously reconsidered, as this vector often leads to the recolonization of invasive species and can result in potentially high subsequent costs. The roots of Japanese knotweed grow several meters deep and can cause significant damage to buildings. These fast-growing, perennial plants are extremely invasive, forming dense stands that displace native, site-adapted, slope-stabilizing vegetation. The dieback of the above-ground parts of the plant in autumn increases the risk of erosion along waterways.
Canadian goldenrod and giant goldenrod (Solidago canadensis, Solidago gigantea) remain popular ornamental plants and, like Himalayan balsam, are also valued by beekeepers as forage plants for bees. These perennial species proliferate primarily along railway and road embankments. They reproduce via seeds (approximately 19,000 per plant) and root runners. Spread occurs through wind, soil, flowing water (root fragments), and garden equipment. The root runners form a dense network, making control extremely difficult.
Actively combating invasive neophytes in the Styrian Enns Valley – a success story of five years of management and care
In problem areas of the municipalities of Irdning-Donnersbachtal, Stainach-Pürgg, and Wörschach, non-native plant species have been carefully eradicated for the past five years, particularly along protected areas and in wetlands. Visible success has already been achieved through the regular mowing of dominant stands, consistent uprooting before seed formation, and proper disposal, especially of flower heads containing ovules. Following consistent, expert-led work, the invasive species have been significantly reduced in ecologically valuable habitats.
At the annual invasive plant action days, organized by the HBLFA Raumberg-Gumpenstein and the mountain and nature patrol, participants learn about the problems, spread patterns, and control measures. "Clear the hotspots" is the motto, because otherwise these robust plants will overrun valuable habitats. Everyone can help with these measures to bring more plant diversity back to the local cultural landscape.
The management of invasive plant species is also a key focus of the international project "CAMARO-D – Transnational Cooperation for Water Protection and Flood Prevention in the Danube Region." A guide for practitioners is being developed jointly with the Styrian Mountain and Nature Watch and the project partners and will be presented at a practical seminar in spring 2019. Two students from the HBLFA Raumberg-Gumpenstein are intensively studying invasive neophytes in the district as part of their pre-university research project. They are documenting hotspots, researching characteristics and spread patterns, and investigating the effectiveness of various control methods.
The ELER project “Measures to conserve biodiversity in Styrian protected areas and valuable habitats” by the State of Styria and the Styrian Mountain and Nature Watch implements practical and awareness-raising activities on the topic of invasive neophytes.
