Cold Weather Coloration

Cold weather coloration refers to the phenotypic expression of anthocyanins and other pigments in cannabis plants when exposed to lower temperatures, typically below 50°F (10°C) during flowering or late vegetative stages. These water-soluble pigments produce purple, blue, red, or black hues in leaves, bracts, and sometimes flowers. This trait appears across multiple genetic backgrounds and is not reliably tied to a single dominant gene, making it environmentally influenced and variable between generations. Breeders working with cold-climate cultivars have long documented this phenomenon, though the underlying genetic architecture remains incompletely characterized. Color intensity and hue depend on both genotype and temperature stress duration, environmental humidity, and light spectrum during the critical window.

Cold weather coloration is often selected for in breeding programs targeting high-latitude or outdoor cultivation, where temperature fluctuations are unavoidable. Breeders may intentionally expose test plants to controlled low-temperature conditions to identify and stabilize color expression across progeny, though consistency cannot be guaranteed without precise environmental replication.