Indoor growing means raising plants in an enclosed space where all light comes from lamps and the climate is managed with fans, extraction, heaters, dehumidifiers and air conditioning. The grower decides the photoperiod, so photoperiod plants can be held in veg or flowered at any time of year.
In practice
Indoor grows range from a 60 × 60 cm (2 × 2 ft) tent to commercial rooms. The main controlled variables are light intensity (PPFD and DLI), photoperiod, temperature, humidity and VPD, airflow, CO₂ and root-zone conditions. Control comes at a price: electricity, equipment, and responsibility for every condition the sun and weather would otherwise supply.
Benefits are year-round harvests, consistent results and protection from weather and many outdoor pests. Typical problems are heat, humidity in late flower, light leaks and pests that thrive in still, warm air, such as spider mites.
Don't confuse with
- Greenhouse: sunlight plus some control; often with supplemental lights.
- Indoor (slang, quality): "indoor" on a menu means indoor-grown flower, often sold as a quality marker; that is a market claim, not a guarantee.
A dehumidifier removes water vapour from grow-room air, usually by condensing it on a cold coil; it is the main tool for controlling humidity in flower.The daily length of light versus dark; photoperiod cannabis flowers when nights grow long enough, rather than at a fixed age.Photosynthetic photon flux density: the number of PAR photons landing on one square metre each second, in µmol/m²/s; the standard measure of light intensity at the canopy.Daily light integral: the total number of PAR photons a square metre of canopy receives in one day, in mol/m²/day; PPFD multiplied by hours of light.Vapour pressure deficit: how much more water vapour the air could hold at its temperature, in kPa; it is the main environmental driver of transpiration.The root zone is the volume of medium or solution where a plant's roots live, including its water, air, temperature, pH, EC and microbes.A light leak is unwanted light entering the grow space during the dark period; in flower it can delay or disrupt flowering in photoperiod cannabis.Tetranychus urticae, the commonest cannabis mite indoors: a 0.5 mm sap-feeder that stipples leaves pale and spins webbing, breeding fastest in hot, dry rooms.Outdoor growing is cultivating cannabis in the ground or containers under natural sunlight, where the season's day length controls when photoperiod plants flower.Greenhouse growing uses sunlight under a covered structure, adding varying degrees of control over temperature, humidity, light deprivation and supplemental lighting.A perpetual harvest staggers plants at different stages, usually with separate veg and flower spaces, so that harvests come every few weeks instead of once per cycle.
