The temperature environment is suitable there are 5 to 7 days also to germinate.

Onions are both cold and heat resistant during their nutritive growth. The temperature range for effective growth is 7 to 35 degrees:. Seeds germinate slowly at 2~3 degrees, and rapidly at 13~20 degrees: temperatures,7~10 days to emerge from the soil. The suitable temperature for plant growth is 19~25 degrees Celsius, below 10 degrees Celsius: growth is slow, above 25 degrees Celsius: growth is poor, the plant is weak, the leaf body is yellowing, and the quality of the leaves and pseudostems formed is poor. The optimum temperature through vernalization is 2?7 degrees. Onions are extremely cold-resistant, and the above-ground part is not subject to frost damage at low temperatures of -10 degrees:. Its ability to withstand cold depends on the characteristics of the variety and the accumulation of nutrients in the plant. Seedlings are too small and have low cold tolerance, and plants that have been exercised or are in a dormant state have significantly higher cold tolerance. So autumn sowing seedlings, sowing early, winter seedlings larger, high rate of shoots; sowing too late, winter seedlings are very small, low cold tolerance, easy to die.