S1 stands for selfed first generation, a breeding term used when a selected female cannabis plant is reversed to produce pollen and then used to pollinate itself, or a genetically identical clone of itself. This is a specific type of feminised breeding, often used to preserve and explore the traits of a standout female plant without introducing genetics from a separate male or female parent.

For growers, the S1 label offers insight into a strain’s breeding method and its connection to a selected parent. S1 seeds can help reproduce key traits from an elite clone or prized female, such as flavour, aroma, potency, resin production, colour, structure, or flowering time. They may also show some variation, making them interesting for growers who want to explore different expressions of a famous or highly selected genetic line.