Heavy rains damage open-field strawberries as more growers switch to tunnels

Heavy rains have damaged open-field strawberry crops in Finland, increasing the risk of mold and softening the fruit, according to a report by Yle.

Growers are now removing affected plants and discarding spoiled berries, though the overall harvest is still expected to be reasonable. Vesa Koivistoinen, a strawberry farmer in Lahti, said quality has varied due to the weather but remains hopeful for a decent yield despite current challenges.

The use of polytunnels has risen sharply over the past decade, from 10 hectares in 2016 to 89 hectares last year, as growers seek protection from erratic weather. Tunnel cultivation also offers more stable growing conditions, better berry quality, and an extended harvest season. Some farmers, like Jussipekka Markkanen of Tyrvännön Marja ja Vihannes in Hattula, adopted tunnel farming 14 years ago. His 94 tunnels allow for consistent supply to stores and reduced need for chemical pesticides, thanks to biological pest control.

Not all growers are making the switch. Koivistoinen’s farm has stuck with open-field cultivation for 91 years, arguing that tunnel-grown strawberries—often cultivated in coconut fiber—are not the “right way” to grow the fruit.

Sirkku Holttinen, chair of the Häme district of the Berry and Fruit Growers’ Association, noted that strawberries thrive in cooler temperatures around 18–20°C, though they also need sunlight. While Finland braces for a heatwave, temperatures above 25°C may become excessive for the crop. She added that tunnel plastics use advanced technology to optimize sunlight for sugar content, but flavor can differ between open-field and tunnel-grown varieties due to differing cultivars.

The main strawberry season is underway, with supply expected to last until late August for fresh berries and late September for packaged ones in stores.