Long Night Requirement

Long Night Requirement refers to cannabis varieties that necessitate extended periods of uninterrupted darkness to initiate and complete flowering. This trait is primarily observed in photoperiod-dependent cultivars, particularly those derived from equatorial or high-altitude landraces where natural daylight cycles remain relatively consistent year-round. Breeders working with these genetics often classify them by their critical dark period thresholds—typically 12–14 hours of continuous darkness needed to trigger flowering reliably. Understanding long night requirement is essential for controlled indoor cultivation, as even brief light interruptions during the dark cycle can delay or prevent flowering onset. This characteristic contrasts with autoflowering varieties, which flower independently of photoperiod, and with cultivars adapted to shorter critical dark periods.

Breeders selecting for long night requirement genetics prioritize consistency in greenhouse and outdoor timing, especially in regions with variable seasonal light patterns. Stabilizing this trait through backcrossing and phenotype selection helps create cultivars suited to specific growing environments and harvest windows.