Onions are highly adaptable to temperature. Seeds and bulbs can germinate slowly at 3～5℃, and start to accelerate at 12℃. The suitable temperature for growth of seedlings is 12～20℃, leaves at 18～20℃, bulbs at 20～26℃, robust seedlings can withstand 6～7℃ The low temperature. Bulb expansion requires a higher temperature, bulbs can not expand below 15 ℃, the best growth is 21-27 ℃. If the temperature is too high, it will grow and decline and enter dormancy.
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