Different strains of cannabis exist because of genetic variation. Genes control the production of cannabinoids and terpenes — the active ingredients in marijuana.
Gene pools of all plants change over time. Cannabis was one of the earliest plants to be cultivated by humans, which is why its gene pool today is so diverse.
While new strains of cannabis continue to be developed through hybridization, others have been preserved over centuries. These strains are referred to as landrace strains. Landrace strains are unique because of their geographical origins. Many are native to central Asia, where the cannabis species originated.
Genetic variation is hard to avoid. Environmental factors influence how genes are expressed, meaning plants with the same genes may show different characteristics if grown in different conditions.
As a result, it is difficult to produce cannabis with consistent THC and CBD levels. Commercial growers often grow cannabis indoors and maintain various environmental controls in order to achieve as much consistency as possible.
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