Suitable Planting Times for Vegetables in Northern China

Note from Bumper Harvest Veggie Girl:The two tables above are for reference only! The specific timing should be decided according to local planting practices, characteristics, varieties, and so on!

Suitable growing temperatures for common greenhouse vegetables

Tomato

• The suitable temperature for growth is 13-28°C;

• The minimum temperature for seed germination is 10°C, the maximum is 35°C, and the optimum is 28-32°C;

• During flowering, 25°C during the day and 17°C at night is best;

• During fruiting, 25-28°C during the day and 16-20°C at night;

• The optimum temperature for tomato root growth is 20-22°C; the minimum soil temperature is 8°C, and the maximum is 32°C.

• Problems caused by unsuitable temperatures:

1. When the temperature is below 15°C, growth is slow, and flowering may fail or pollination may be poor; at 5°C, stem and leaf growth stops; below 1°C, the plants begin to freeze to death.

2. Tomatoes are not tolerant of heat; above 35°C, flowering and fruiting are affected; at 40°C, growth stops; at 42°C, if air humidity is below 50%, the seedlings may be scorched.

3. During the seedling stage, the minimum temperature must not be lower than 13°C and must not be higher than 33°C, otherwise flower bud differentiation is affected;

4. 19-24°C is favorable for the formation of lycopene, while below 15°C or above 30°C is not favorable for lycopene formation.

5. For early-spring tomatoes, the transplanting time should be when the soil temperature has steadily reached above 8°C.

Pepper

• The suitable temperature for seed germination is 15-30°C, with 25°C being the optimum;

• The suitable temperature for fruit development and color change is 20-30°C;

• Pepper transplanting requires the soil temperature to steadily pass 10°C before it can be done.

• Problems caused by unsuitable temperatures:

1. Above 30°C, the floral organs develop incompletely or the stigma dries up and cannot be fertilized, causing flowers to drop.

2. During flowering, the minimum temperature is 10°C, otherwise fertilization cannot occur.

Eggplant

• The suitable temperature for growth is around 25°C; below 20°C, growth and development are slow, and below 15°C, growth basically stops;

• It is best when both daytime and nighttime temperatures are close to 25°C;

• During flowering, 25°C during the day and 17°C at night is best;

• The optimum temperature for seed germination is 28-30°C;

• During the seedling stage, the minimum temperature must not be lower than 15°C and must not be higher than 33°C, otherwise flower bud differentiation is affected.

• Problems caused by unsuitable temperatures:

1. Studies have shown that when the night temperature is 17°C, the higher the daytime temperature, the shorter the time to flower formation, but the fewer the robust flowers;

2. When the daytime temperature is 25°C, the higher the nighttime temperature, the shorter the time to flower formation, and the fewer the robust flowers.

Cucumber

• The suitable temperature for growth is 18-30°C, with 24°C being the optimum;

• The cucumber growing period requires a certain day-night temperature difference. Generally, 25-30°C during the day, 18-20°C in the first half of the night, and 12-15°C in the second half of the night, with a day-night temperature difference of about 10°C being best;

• Low nighttime temperatures help reduce the plant's respiratory consumption.

• The minimum temperature for seed germination is 12.7°C, the maximum is 38°C, and the optimum is 28-32°C;

• During the seedling stage, the minimum temperature must not be lower than 13°C and must not be higher than 33°C;

• The optimum soil temperature for root growth is 20-22°C, the minimum soil temperature is 12°C, and the maximum is 38°C.

• Problems caused by unsuitable temperatures:

1. Seed germination develops slowly below 18°C, and the germination rate decreases above 35°C;

2. The maximum temperature is 45°C, at which the plants wither and die. When above 32°C, respiration increases; above 35°C, growth and development are poor; above 40°C, flowers drop and fruits abort.

3. Roots begin to rot at a maximum of 38°C, and above 32°C root respiratory consumption increases;

4. For early-spring cucumbers, the transplanting time should be when the soil temperature has steadily reached above 12°C.

Cowpea

• The suitable temperature range for the entire growing period is 20-32°C;

• The suitable temperature for seed germination is 25-35°C, with a minimum of 10°C and a maximum of 38°C;

• Problems caused by unsuitable temperatures:

1. At high temperatures below 35°C, stems and leaves still grow, but flowers and fruits tend to drop, and the plants tend to age, reducing the edible quality of the product;

2. Cowpea is afraid of low temperatures; below 15°C, growth is slow; at 10°C, it is inhibited; at 5°C, it is damaged by cold; at 0°C, it dies.

Common bean

• The suitable temperature for seed germination is 20-25°C;

• The suitable temperature during flowering is 18-25°C;

• The suitable temperature for seedling growth is 18-20°C.

• Problems caused by unsuitable temperatures:

1. Seeds do not germinate easily below 8°C or above 35°C;

2. Seedling growth stops below 13°C;

3. During flowering, below 15°C or above 28°C, fruiting cannot occur, and a large number of flowers drop;

4. Sowing common beans requires the soil temperature to steadily pass 10°C before it can be done.

Celery

• When cultivating celery in a greenhouse, the daytime temperature should preferably be 15-23°C, not exceeding 25°C at most, and around 10°C at night, not lower than 5°C;

• On cloudy, rainy, snowy, and windy days, the temperature should be appropriately lower, but not too low, to prevent cold damage and early bolting;

• Ventilate appropriately according to humidity to reduce air humidity and reduce diseases; this can be used together to reduce respiratory consumption and make the leaf stalks plump and thick.