The photoperiod is the amount of time the plant needs to be exposed to light at different stages of growth. This is usually expressed as a 24-hour day/night ratio. For example, most cannabis plants require 18 hours of light and 6 hours of total darkness during their vegetative period, while they typically require 12 hours of light and 12 hours of total darkness during flowering. It should be emphasized that the photoperiod of cannabis needs to remain relatively undisturbed; Try not to change the photoperiod frequently and unsteadily.

The photoperiod controls each stage of plant’s life—the growing or flowering period. Therefore, plants rely on light-sensitive cells called photosensitive pigment. During the day, exposure to red light causes photosensitive pigments to enter a higher energy state. In this high energy state, short-day plants, such as hemp, do not flower.

The farmer controls the phase of vegetative growth by keeping the photosensitive pigment stimulated. This is done by keeping the lights on for 18 hours. Some growers will say it can be extended by 24 to 24 hours, but plants, just like humans, need rest, so I think it's best not to have more than 20 hours of light, but more than 4 hours of rest.

Photosensitive pigment need about 12 hours of darkness to "relax" enough for them to flower. That's why cannabis growers change their light cycles to 12 and 12 hours to force their plants into bloom.

However, time is not the only factor that affects photosensitive pigments. Plant pigments can also be activated by exposure to far-red light. Some elite growers are experimenting with keeping up to 14 hours of light and then exposing the garden to far-red light for a short period of time (15-20 minutes).This far infrared exposure accelerates the conversion of photosensitive pigments to ground state.

The reason for the extended day experiment is to allow plants to spend an extra two hours a day photosynthesizing while still in bloom. This equates to a 16% increase in harvest efficiency.

Different varieties have different needs when it comes to their photoperiod, so it's best to choose a variety based on your specific hemp growing needs. Sativas, for example, usually needs more light to flower because it comes from tropical regions where 12/12 sunlight is perfectly balanced throughout the year. Indica originated in parts of the world where natural light cycles are less balanced and may require less light time to flower. Finally, automatic seed varieties do not require a specific photoperiod scheme to flower.