Concerns rise over invasive yellow water-lily in Turku, Finland

In the morning light, the beautiful yellow flowers of the yellow water-lily are not only attractive but also deceptive, as they smother other aquatic plants and spread rapidly. In Turku, the Aurajoki Foundation, which protects the cultural environment along the Aura River, is contemplating ways to control the invasive species. The last community effort to combat the plant took place last summer.

Eelin Hoffström-Cagiran, the Foundation’s executive director, mentioned that most research on controlling this plant has been conducted in stagnant waters, while the Aura River has a flowing current. Attempts to wade in wearing rubber boots failed due to deep waters, and mowing the plants only caused them to split and spread further.

Although yellow water-lily has not yet been listed on Finland’s national list of harmful invasive species—making it difficult to secure funding for its control—other plants such as giant hogweed, Japanese rose, and Himalayan balsam are included.

The yellow water-lily was first recorded in the wild in Finland in 2012 at Lake Littoisten. It has since been found in other areas, including Naantali, Masku, and Raisio. Arno Kasvi, a horticulturist, noted that the extended growing season, influenced by warmer weather, aids its spread.

Another contributing factor to the plant’s proliferation is its efficient seeds, approximately three millimeters in size with small hooks that cling to birds’ feathers, facilitating its dispersal. Kasvi indicated that it is likely that the yellow water-lily was introduced to Finland as an ornamental plant.

Local canoe operator Pasi Vesterinen expressed concern over the dramatic increase in yellow water-lily, highlighting that the population of water lilies in the area has diminished significantly in recent years.