Invasive Himalayan balsam reaches 200 sites in Lappeenranta

Invasive Himalayan balsam has spread to about 200 locations in Lappeenranta, where the city has been working to eradicate it, Yle reports.

The plant crowds out other vegetation and can significantly reduce water quality when it grows along rivers. It is included on the European Union list of invasive alien species, which means landowners must control it on their own property.

One plant can produce about 4,000 seeds. When its seed pod bursts, it can propel the seeds up to seven metres away.

Maisa Hautala, who is responsible for maintaining Lappeenranta’s green spaces, said the city regularly removes and pulls up the plant at 200 locations.

Residents can also pull up Himalayan balsam in Lappeenranta. The entire plant must be removed from the ground with its roots, and the waste must be placed in a sealed plastic bag so that the seeds cannot spread.

Control work must continue for three years. The area should then be monitored for a further two years to ensure the plant does not return.

Biologist and invasive species expert Markus Seppälä said the plant’s harmfulness depends partly on where it grows. Along a river, it is more damaging than near a residential area because it can significantly weaken water quality.

The plant spreads only through its seeds. The seeds can travel in soil, garden waste and animal fur, while rainwater and melting snow are also important means of transport.

Seppälä said municipalities and cities play an important role in controlling invasive species because they often have the best knowledge of local conditions. Clear plans help them use limited funding and other resources effectively.

Invasive species are a major threat to biodiversity worldwide. Finland has fewer problems with them than southern Europe, Australia or the United States, but climate warming could allow species that have previously struggled to survive in Finland to establish and reproduce. These could include harmful insects and plant diseases.

Seppälä said Finland should focus on prevention as well as removal by preventing new invasive species from entering the country and improving understanding of how they spread.