When to Plant Tomatoes? A Detailed Guide to the Latest Planting Times

Tomatoes are warm-loving plants. The suitable daytime temperature is 25-28°C, and at night 16-18°C. Below 15°C, tomato seed germination, pollination and fertilization, and fruit ripening are affected; below 10°C, growth is slow and reproductive development is inhibited; at 5°C, stems and leaves stop growing; at 2°C, they suffer cold damage; at 0°C, they are frozen to death. Above 35°C, reproductive development is affected; above 40°C, physiological functions are disrupted and the plants die from heat. Sufficient light and a suitable temperature difference between day and night help accumulate nutrients and promote ripening, promote healthy plant development, prevent spindly growth, enhance the tomato's disease resistance and stress resistance, and increase yield.

 Tomato Planting Times

Generally speaking, tomatoes are divided according to planting and harvest time into spring tomatoes, autumn-winter crops, winter-spring crops, and overwintering crops, and so on. Below, let us look at their planting times separately!

1. Planting time for spring tomatoes

The suitable seedling age for open-field spring tomato cultivation is 50-70 days, meaning sowing should be done 50-70 days before transplanting. For example, in the Shenyang area at 41 degrees north latitude, spring-crop tomatoes are sown and raised as seedlings in protected facilities in February, and transplanted into the open field after the late frost in early May.

Spring tomatoes are generally transplanted immediately after the local late frost period, when the soil temperature at a depth of 5-10 cm in the plow layer stably passes 12°C. For example, the average late frost date in the Shenyang area over the years is May 2, and the suitable transplanting period is generally May 6-10. In the Yangtze River basin, it is generally around Qingming; in North China, around Guyu; and in Northeast China, generally around Lixia. With windbreaks, plastic film mulching, and leeward, sunny, high, dry sandy land, transplanting can be done earlier. Transplanting also depends on the weather; if there is rain and strong wind, transplanting should be appropriately delayed. During the suitable transplanting period, transplanting should be done as early as possible. Shaanxi tomatoes are mainly planted according to market time, with two main seasons a year: one is delayed cultivation after autumn, with seedlings raised after July or August and coming to market successively from November onward; the other is early spring cultivation, with seedlings raised in November or December and coming to market in May or June.

2. Planting time for autumn-winter crops

Autumn-winter crops are generally sown and raised as seedlings from mid-to-late July to early-to-mid August, and transplanted from mid-to-late August to early September. Film is put in place from mid-to-late September to early October, and harvesting runs from late November to early February of the following year.

3. Planting time for winter-spring crops

Winter-spring crops are sown from early November to early December, transplanted from mid-to-late January to early February of the following year, and harvested from early-to-mid March to June.

4. Planting time for overwintering crops

Overwintering crops belong to single long-season cultivation. They are generally raised as seedlings from mid-to-late September to early October, transplanted in November, and harvested starting in January of the following year.

Tomato Seed Treatment

1. Hot-water seed soaking

Hot-water seed soaking is an effective measure to break seed dormancy, promote seed germination, sterilize and prevent disease, and enhance seed resistance. The specific method is:

① Soak the seeds in clean water for 1-2 hours.

② Remove them and place the seeds in warm water at 55°C, maintaining the water temperature evenly and soaking for 15 minutes, then continue soaking for 3-4 hours before promoting germination. For hot-water seed soaking, generally use one part seeds to two parts water. At the same time, stir constantly and quickly so the seeds are heated evenly and to prevent scalding the seeds.

③ Keep adding hot water to maintain the water temperature at 55°C. This disinfection method can prevent the occurrence of tomato leaf mold, canker, early blight, and other diseases.

2. Chemical disinfection

① Trisodium phosphate seed soaking: first soak the seeds in clean water for 3-4 hours, remove and drain them, then place them in a 10% trisodium phosphate solution for 20 minutes, wash clean with water, and then promote germination. This method has a relatively obvious effect on tomato viral disease.

② Formalin solution seed soaking: place pre-soaked and swollen seeds in a 1% formalin solution for 15-20 minutes. During soaking, keep the container sealed to prevent the liquid from volatilizing, then take them out, wrap them in a damp cloth, and place them in a sealed container to sweat for 2-3 hours. Rinse them repeatedly with clean water, then soak and promote germination. This method can reduce or control the occurrence of tomato early blight.

③ Soak the seeds in 0.1% potassium permanganate solution for 15-30 minutes, which can effectively reduce the occurrence of tomato mosaic virus disease and early blight.

④ Place pre-soaked tomato seeds in 1000 mg/kg agricultural streptomycin solution for 30 minutes, which is quite effective for controlling bacterial wilt.