Light deprivation is the practice of shortening the day artificially for sun-grown plants by pulling an opaque cover over them each evening and removing it in the morning, so they get roughly 12 hours of uninterrupted darkness. Photoperiod cannabis responds by flowering, even in midsummer when natural nights are short.
In practice
Light dep lets greenhouse and outdoor growers harvest in summer, before autumn rain and mould, and run two or more crops per year. Covers must be truly lightproof and pulled at the same time every day; inconsistency or leaks can cause re-veg or stress. Under covers, heat and humidity build quickly in warm weather, so ventilation and fans are important.
Automated blackout curtains do this on a timer in commercial greenhouses; small growers use tarps on frames.
Don't confuse with
- Darkness before harvest: a separate idea (24-72 h of dark before chopping) that GenetixBay classes as a myth.
- Indoor flip: the same switch done with a light timer.
The daily length of light versus dark; photoperiod cannabis flowers when nights grow long enough, rather than at a fixed age.Re-veg is returning a flowering or harvested plant to vegetative growth by putting it back under long days, often to save a genotype after harvest.A large palmate cannabis leaf with several long leaflets on a long petiole; fan leaves do most of the plant's photosynthesis and carry few trichomes.The practice of keeping plants in total darkness for 24-72 hours before cutting to boost resin; GenetixBay rates it a Myth and runs a standing challenge against it.Greenhouse growing uses sunlight under a covered structure, adding varying degrees of control over temperature, humidity, light deprivation and supplemental lighting.Outdoor growing is cultivating cannabis in the ground or containers under natural sunlight, where the season's day length controls when photoperiod plants flower.The flip is switching a photoperiod plant from long vegetative days to a flowering light schedule, usually around 12 hours of light, to start flowering.
