When Tomatoes Hit the Winter: A Counterattack to Overwinter Production in Soft-Shell Solar Greenhouses in North China

In North China, the overwintering production of the tomato (Solanum lycopersicum L.) encounters difficulties posed by extreme weather conditions and the high costs of traditional greenhouses. Soft-shell solar greenhouses present a viable alternative because of their low cost and excellent heat-retaining properties. This study establishes a technical framework for high-yield and high-quality winter tomato production in soft-shell greenhouses through analyzing dynamic light, temperature, and humidity parameters, cultivar responses, and optimized production–marketing models. Field experiments monitored microclimate data in soft-shell solar greenhouses during different growth stages of six cherry tomato and three large tomato varieties, combined with yield, quality, and economic return analysis. The results showed that (1) soft-shell greenhouses increased average daily temperatures by 10–15 °C, reduced low-temperature stress duration by 25%, achieved 82% light saturation compliance, and decreased humidity fluctuations by 23%; (2) the yield per cluster of cherry tomatoes increased first and then decreased for early maturing varieties, and decreased for middle and late maturing varieties, while the yield of large tomatoes decreased first and then increased; (3) light intensity was positively correlated with Brix accumulation, and humidity was negatively correlated with yield; (4) cherry tomato yields were more temperature-sensitive, whereas large-fruited tomatoes were more influenced by light intensity; (5) a “variety optimization + scenario-based sales” model integrating multi-cultivar layouts and gift-box marketing strategies improved economic returns. This research provides an integrated environmental regulation and market adaptation solution for North China’s protected agriculture, offering a reference value for greenhouse agriculture development in global cold regions.