Flowering Stage

The flowering stage begins when a photoperiod cannabis plant detects sustained darkness exceeding 11 hours per day, triggering the phytochrome system to convert from vegetative to reproductive growth. Indoor growers initiate flowering by switching the light cycle from 18/6 to 12/12; outdoor plants flower naturally as days shorten in late summer and fall. Flowering progresses through distinct phases: Week 1-2 (transition/stretch) — plants double in size, sex can be confirmed via pre-flowers, internodal spacing extends; Week 3-4 (early flower) — calyxes form at bud sites, white pistils appear, structural growth slows; Week 5-6 (mid flower) — buds swell and densify, trichome production accelerates, terpenes begin developing aromatic complexity; Week 7-8 (late flower) — buds reach maximum density, trichomes shift from clear to cloudy, pistils begin browning; Week 9+ (ripening/finishing) — trichomes shift from cloudy to amber indicating peak THC then degradation to CBN, late-flush nutrient reduction prepares for harvest. Critical flowering parameters: temperature 65-80°F (cooler nights bring out purple colors and protect terpenes), humidity 40-50% RH (lower humidity prevents bud rot), absolute darkness during dark period (any light leak above 2 lux triggers stress and potential hermaphroditism), nutrient profile shifted to higher P-K ratios (NPK 1-3-2 or similar), and CO2 supplementation up to 1500ppm under high light. Total flowering time defines harvest scheduling and determines whether a strain fits your climate and grow plan.