Hemp has different requirements on temperature with different varieties.
Generally, from sowing to maturity, the accumulated temperature of which is greater than or equal to 0℃ is 1900-2000℃, and that of which is 2700-3000℃.For early maturing varieties, the accumulated temperature of 1600-1700℃ can reach the process maturity.Hemp seeds can germinate when the soil temperature is above 1℃, but the seedlings should be orderly, generally it is advisable to sow when the soil temperature is above 8-10℃.The optimal temperature for germination of hemp seeds is 25-35℃, and the highest temperature is no more than 45℃. However, the seeds germinate quickly and evenly when the temperature is high.Hemp seedlings can tolerate -5 low temperature in a short time, but its growth process will be seriously affected.
Suitable growth temperature, seedling stage is 10-15℃;The rapid growth period was 18-30℃, and 19-25℃ was the most suitable.After flowering, the seeds mature to 18-20℃, and the flowering stage meets the low temperature of -1℃, the flower apparatus is damaged, and the flower apparatus dies below -2℃, especially male flowers.Seeds can withstand low temperature and lower temperature of 3-5℃ within 10-15 days after germination;At a low temperature of -5℃, its growth will be delayed a little.However, if adequate water and nutrients can be supplied, the low temperature in seedling stage has little effect on later development and yield.In 1957, after the emergence of hemp seedlings in the main hemp producing area in shandong, the growth of hemp was not affected when it was frozen in the shower.
Northern shaanxi province has the habit of sending seeds the first winter.Winter sowing experiments in heilongjiang and jilin provinces were successful.All these indicate that cannabis plants have a strong ability to resist low temperature at the seedling stage.
Hemp is not tolerant to low temperature during flowering, and it is easy to die when it encounters sub-zero low temperature during flowering, especially the male plant dies more.During the growth period, the average temperature of day and night has a great influence on the growth of cannabis, especially from bud to the end of flowering, the growth of stem is the fastest and dry matter increases greatly.During this period, the optimal temperature should be maintained around 16(night)-25f (day).