Effect of shade treatment on the growth and vitality of cloudberry Rubus chamaemorus

Cloudberry Rubus chamaemorus is a promising new berry species for cultivation in Latvia. This study aimed to assess how different shade levels influence cloudberry growth and vitality in semi-controlled conditions. Cloudberries (variety ‘Nyby’) were planted in enclosed planting area and grown under four shading treatments, using shading nets: control (no shade), 30%, 50%, and 80% shade for two years. Non-destructive SPAD measurements were taken weekly during the growing season (from May to August) in both years. Leaf size was measured at the end of August in both years, while leaf density and leaf nutrient concentrations were determined at the end of August in 2024. The results revealed significant differences between treatments for all of the measurements, with the highest values observed in plants under the 80% shade in both years. In the second year, the 50% an 80% shade treatments had similar results. Overall, the highest plant vitality was observed under 50% and 80% shade, demonstrating that netting effectively protects cloudberries from excessive sunlight. While larger leaves might improve light capture, they also require additional energy, potentially reducing resources available for fruit production. Thus, we suggest the 50% shade to be the most effective for cloudberries in the Latvian climate, as it balances protection with optimal energy conservation. Additionally, optimal fertilizing in the field could improve plant health and yield, therefore further studies regarding the combined effects of shade and fertilization on cloudberry production are required.