In general, tomatoes enter the domestic market in large volumes between June and September. Market supply is extremely large in this season, and greatly exceeds the ability of domestic consumers to absorb this volume. The price of tomatoes is quite regular in this period. The season has changed, however, and we have entered a colder period. People still eat tomatoes at the same rate, but the cost price of tomato production greatly increased because of the shift to greenhouse production.
Regular, open-field tomatoes from all production areas in the north and most production areas in the south, have almost completely disappeared from the market. Greenhouse tomatoes have taken over the market, although several production areas in south China still supply open-field tomatoes. Shouguang in Shandong and Bo'ao in Hainan supply winter season tomatoes. Their supply volume, however, is relatively small, while demand remains strong. Naturally, the price of tomatoes increases.
Source: Spring Talk Stories Baijiahao