While the supply of wild harvested cranberry (Vaccinium oxycoccos) is not adequate, field cultivated cranberry (V. macrocarpon) are imported to Finland from North America. Our goal is to enable sustainable and economically viable cranberry production in the Northern latitudes utilizing high tunnel soilless table-top cultivation technology. While we have tested several North-American cranberry cultivars in a high polytunnel, cv. Pilgrim proved to be the most productive and precocious under the Northern conditions.
Through a European Innovation Partnership -project 'Cranberry Innovation' (2025-27), the technique we have developed at the University of Helsinki, is put into practice on berry farms. In collaboration with the berry growers and the rural advisory service Pro-Agria Etelä-Suomi, we optimize the production technique to ensure its effectiveness in commercial berry cultivation.
We have tested several commercial and tailor-made substrates and determined nutrient requirement of cranberry plants in substrate culture. Winter survival of cranberry roots is critical in substrate culture and is affected by the type of substrate. Sphagnum moss, having many beneficial characteristics, can be used to replace peat as a substrate for cranberry.
We have studied different pruning strategies to optimally steer the balance between fruiting and vegetative growth of cranberry plants in high tunnel cultivation. Fruit thinning can be used to increase fruit weight and to overcome the strong biennial bearing tendency of cranberry uprights.
High tunnel conditions, fertilization and substrate are factors that affect postharvest quality and shelf life of cranberry fruit. We have also examined, how different light spectra applied postharvest affect the quality variables (ethylene production, anthocyanin synthesis, and color) of cranberry fruit harvested at different maturity stages.