The Keltalammikki-VEX Project Seeks Solution to Control the Spread of Yellow Fringed Lily in the Aura River Using Floating Covers 

Aurajoki Foundation is launching a two-year project to develop a surface covering method for controlling yellow fringed lily in the Aurajoki River. The project aims to address thegrowing need to curb the spread of this harmful invasive species. Yellow fringed lily reduces the recreational use of the river and displaces the area’s native aquatic vegetation. 

Previous control methods based on cutting and hand-pulling have proven labor-intensive and ineffective. Additionally, hand-pulling can cause plant fragments to break off, whichmay be carried downstream and spread the plant to new locations. 

The effectiveness of the floating covers is based on blocking sunlight from reaching the plant leaves, which efficiently suppresses the growth. Compared to bottom-installedsolutions, floating covers offer easier monitoring and management, which is especially important in flowing waters. 

The goal of the Keltalammikki VEX – project is to develop an operational model that enables effective and safe control measures. A similar control method has been tested in waters near Tingsryd, Sweden, and the lessons learned there will also be applied in the Aura River. 

Yellow fringed lily is an invasive species in Northern Europe that has spread to the region through garden plantings. It is a striking but harmful floating-leaved aquatic plant that forms dense stands. These stands inhibit fishing and swimming and smother native aquatic plants. The first observations of yellow fringed lily in Southwest Finland date back to 2012. The species was first recorded in the Aura River in 2015, after which its spread has been rapid. Measurements from summer 2025 show that the plant covers 50,000–60,000 square meters of the river’s surface. 

The project is co-funded by the EU rural development fund, granted by the Centre for Economic Development, Transport and the Environment (ELY Centre) of Southwest Finland, whose duties are now managed by the Regional Centre for Economic Development Centre of Southwest Finland. Additionally, funding has been received from the Raija and Ossi Tuuliainen Foundation.