The study investigated the influence of container color on substrate temperature, plant growth and development, and fruit quality of highbush blueberry (Vaccinium corymbosum L.) cv. ‘Bluecrop’. The experiment was conducted in an unheated plastic tunnel at the Experimental Field of the Biotechnical Faculty, University of Ljubljana. Forty plants were grown in black, white, silver, and green containers filled with the same substrate. Measurements included substrate temperature, phenological development, yield, and selected fruit quality parameters (berry mass, firmness, soluble solids, titratable acidity, total phenolic compounds, and anthocyanins). The experiment lasted from budburst to the end of the harvest period. The average substrate temperature in black containers was approximately 5 °C higher than in silver ones, and plants in black containers reached certain phenological stages several days earlier than those in lighter-colored containers. The highest yield was recorded in black containers (1338 g per plant), and the lowest in green ones (940 g per plant). Soluble solids content in berries ranged between 10.7 and 11.1 °Brix, with the highest values measured in fruit from silver containers. The results indicate that container color affects the substrate temperature in the root zone. The highest substrate temperatures, exceeding 31 °C, were recorded in black containers, while in all other colors the temperature did not exceed 28 °C (from budburst to harvest in 2024). Although phenological stages occurred earlier in black containers, no earlier fruit ripening was observed. Container color did not have a significant effect on fruit quality parameters. Considering the influence of multiple interacting factors, further detailed research is recommended to support the development of optimal container production technologies for highbush blueberry.
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