Cannabis Flowering Stage: Complete Guide for Dense Resinous Buds

The transition to flowering

For photoperiod plants, flowering begins when you switch the light cycle to 12 hours on and 12 off (12/12). During the first two weeks, the plant stretches, growing 50% to 100% taller. This is normal. The plant is preparing to produce flowers. Avoid aggressive pruning during this phase as the plant uses all energy for vertical growth.

Flowering nutrients

During flowering, nutrient needs change. Nitrogen (N) should be reduced while phosphorus (P) and potassium (K) increase. Use bloom-specific fertilizers with NPK like 1:3:2. Add PK boost during weeks 4-6 for density and resin. Ideal EC rises to 1.6-2.2 mS/cm (soil) or 1.8-2.4 mS/cm (hydro). In the last two weeks, flush with plain water to remove excess salts.

Temperature and humidity during flowering

Ideal flowering temperature is slightly lower than veg: 68 to 78°F (20 to 26°C). Above 82°F (28°C) can reduce terpene production. Relative humidity should drop progressively: 50-60% early flower, 40-50% mid, 30-40% late. High humidity late in flower increases mold (botrytis) risk, which can destroy an entire harvest in days. Invest in good ventilation.

Maturity signs: trichomes

The best maturity indicator is the trichomes (resin glands that look like crystals). Use a 30x to 60x loupe or microscope. Clear trichomes: plant is not ready. Milky/opaque: THC peak, ideal for cerebral effect. Amber: THC degrading to CBN, more relaxing effect. Many growers harvest when 70-80% are milky and the rest amber, balancing effect and potency.

Maturity signs: pistils

Pistils (white hairs on buds) also indicate maturity. Early flower: white and erect. As buds mature, pistils change to orange, brown or red and retract into the calyxes. When 70-90% of pistils have changed color, the plant is near harvest. But pistils are less precise than trichomes as they may change color from other factors like heat.

Common flowering problems

Bud rot (botrytis) is the biggest enemy. It appears as gray mold inside buds and spreads fast. Prevention is best: keep humidity low and ventilation active. Phosphorus deficiency shows as purple spots on leaves: increase PK. Light burn appears as white or brown buds closest to the light source: increase distance. Yellow lower leaves are normal late in flower as the plant consumes reserves for bud production.