Critical Day Length
Critical Day Length refers to the photoperiod threshold at which a cannabis plant transitions from vegetative growth to flowering. This threshold varies by cultivar and geographical origin; equatorial and near-equatorial landraces often flower at longer day lengths (12–14 hours), while higher-latitude genetics may initiate flowering at 13–15+ hours. Breeders working in controlled environments use critical day length data to predict flowering timing and select for photoperiod stability. Understanding a strain's critical day length is essential for indoor cultivation planning and outdoor harvest scheduling across different growing regions.
Critical Day Length strains
No strains tagged into Critical Day Length yet — they'll appear here as breeders submit lineage records under this classification.
Critical Day Length refers to the photoperiod threshold at which a cannabis plant transitions from vegetative growth to flowering. This threshold varies by cultivar and geographical origin; equatorial and near-equatorial landraces often flower at longer day lengths (12–14 hours), while higher-latitude genetics may initiate flowering at 13–15+ hours. Breeders working in controlled environments use critical day length data to predict flowering timing and select for photoperiod stability. Understanding a strain's critical day length is essential for indoor cultivation planning and outdoor harvest scheduling across different growing regions.
Breeders document and select for critical day length to develop cultivars suited to specific climates and production systems. Strains with well-characterized photoperiod responses enable predictable flowering windows, reducing crop variability and supporting regional adaptation breeding programs.
Educational reference · Cultivar metadata only · No medical claims