Phenotype Fixation

Phenotype fixation refers to the breeding practice of stabilizing visible and chemical traits across successive generations until a cannabis variety breeds true to type. Breeders working toward phenotype fixation select parent plants that consistently express desired characteristics—morphology, terpene profiles, flowering time, or cannabinoid ratios—then cross and backcross offspring to reinforce these traits. This process typically requires multiple generations of selection and testing to achieve reliable homozygosity. Phenotype fixation is foundational to creating stable cultivars and is commonly documented in both hybrid development and the creation of IBL (inbred line) varieties. The term is often used interchangeably with "stabilization" in breeding literature, though technically phenotype fixation emphasizes the visible expression of selected genetics.

Breeders prioritize phenotype fixation to reduce unwanted variation in commercial crops and to create reproducible seed lines. Achieving fixation allows cultivators to reliably predict plant structure, yield timing, and aromatic profiles across grows, reducing crop unpredictability.