Cannabis plants that are pollinated naturally with traditional breeding techniques can produce both male or female seeds. These are known as regular seeds and, as in most species, they occur with about an even split between the two sexes. That means Cannabis cultivators starting with regular seeds have about a 50% chance of yielding a female plant from each one. When growing Cannabis respectively hemp for production of flowers or biomass for cannabinoid extraction purposes, we are looking to work with female plants only. As a result, growing hemp from regular seeds isn’t efficient.

There are several techniques used for a reliable production of feminized seeds. One classic method is stressing out a healthy female plant by interrupting its light cycle during flowering. While that works to a certain extent, the most common and controlled method is to treat female plants with a colloidal silver or silver thiosulphate solution (STS). These methods make it possible to control the sex of a plant without any genetic modification. Both substances are a blend of water and fine silver particles, and they work in largely the same fashion. The silver solution impedes the production of ethylene, a hormone involved in the flowering process of the plant. The result is a female plant that produces male flowers with pollen sacs. Since those pollen sacs develop on a plant with only female chromosomes (XX), they will produce only female pollen. When this pollen is applied to another, untreated female plant, the seeds produced by this plant will be around 99.99% female.