Day Length Photoperiod

Day length photoperiod refers to the light cycle duration that triggers flowering in cannabis plants. Traditional photoperiod-dependent strains require a shift to shorter daylight hours (typically 12 hours or less) to transition from vegetative growth to flowering. This classification distinguishes photoperiod strains from autoflowering varieties, which bloom based on age rather than light schedule. Understanding photoperiod requirements is fundamental to cultivation planning, as it determines whether a strain must be grown indoors with controlled lighting or outdoors during appropriate seasons. Breeding records frequently note photoperiod sensitivity as a key trait inherited from parent lines, particularly from Cannabis sativa and indica subspecies backgrounds.

Breeders select for photoperiod stability to ensure predictable flowering timing across generations and growing environments. Photoperiod-dependent traits are crossed intentionally when breeders want to preserve traditional growth patterns or avoid autoflowering genetics in their parent selections.