Temperature of the environment

The temperature requirements of cannabis vary with the type of varieties. Generally, from sowing to process maturity, the accumulated temperature greater than or equal to 0℃ is 1900-2000℃, and to seed maturity, the accumulated temperature is 2700-3000℃; for early-maturing varieties, the accumulated temperature of 1600-1700℃ can reach process maturity. Cannabis seeds can germinate when the soil temperature is above 1℃, but the seedlings must emerge evenly. Generally, it is advisable to sow when the soil temperature is above 8-10℃.

The optimum temperature for cannabis seed germination is 25-35℃, and the maximum temperature does not exceed 45℃. The higher the temperature, the faster and more uniform the germination. Cannabis seedlings can withstand short-term low temperatures of -5, but it will seriously affect their growth process. The suitable growth temperature is 10-15℃ in the seedling stage; 18-30℃ in the rapid growth stage, and 19-25℃ is the most suitable; 18-20℃ from flowering to seed maturity. If the temperature is -1℃ during the flowering period, the flower organs will be damaged, and if it is below -2℃, the flower organs will die, especially the male flowers. The seeds can withstand low temperatures of 3-5℃ and lower temperatures within 10-15 days after germination; at a low temperature of -5℃, its growth will be delayed.

However, if sufficient water and nutrients can be supplied, the low temperature in the seedling stage will have little effect on the subsequent development and yield. In 1957, after the hemp seedlings emerged in the main hemp-producing areas of Shandong, they encountered showers and freezing, but the growth of hemp was not affected. There is a habit of sending seeds in the previous winter in northern Shaanxi. Winter sowing experiments in Heilongjiang and Jilin provinces were successful. All these show that the ability of hemp seedlings to resist low temperatures is quite strong.