Cannabis, like humans, requires sleep in addition to growth. In the seedling stage, it takes 6-8 hours of sleep a day; while in the flowering stage, it takes 12 hours. (Note: When the size of the cannabis grows to half of the final size, it can be determined that has entered the flowering stage.) The lighting controller can help you set the switching time and realize the automatic switching of the grow lights.
Cannabis requires different photosynthetic photon flux density (PPFD) during seedling, growth and flowering stages. Low PPFD may affect the photosynthesis on the leaf surface; while too high PPFD may threaten plant metabolism. A 2010 study found that the highest PPFD value of cannabis is 1500-2000μmol∙m-2∙s-1 when the CO2 concentration rises to 750 ppm under environmental conditions of 25-30°C. Under these indoor conditions, the photosynthesis of cannabis is optimized.
However, lighting with an intensity of 1500–2000μmol∙m-2∙s-1 consumes a lot of electricity and is very expensive to run. Most growers use lower intensity light and produce good yields. Only 200 to 400μmol∙m-2∙s-1 PPFD is required to successfully grow seedlings. For cannabis in the vegetative growth phase, PPFD can reach 400 to 600 μmol∙m-2∙s-1. Flowering will benefit from 600 to 900 μmol∙m-2∙s-1 PPFD or higher.
Then how to set PPFD in the corresponding interval? At this time, a PPFD detector is needed. When the height is certain, use the controller to adjust the power; observe the changes of PPFD and adjust to the target interval.