Feminised seed is produced by crossing two females, or a female with herself. One of them is treated so that it grows male flowers and makes pollen (sex reversal), most often with silver thiosulfate (Ram and Sett 1982; Lubell and Brand 2018). Because that pollen carries only X chromosomes, the seed is genetically female (XX).
In practice
Feminised seed saves space and time: no males to find and remove, nearly every plant flowers into usable bud. That is why most seed sold for home growers is feminised.
Its quality depends entirely on the breeder's discipline. Good practice is to reverse only females that have stayed fully female over several runs, under controlled conditions, and to grow out and check the seed before release. Poor practice (reversing a plant that already herms, or using pollen from stress herms) spreads unstable sex expression into the seed.
Feminised seed cannot be used to select males, so lines bred only by feminising lose half of what breeding normally samples.
Don't confuse with
- S1: feminised seed from a female selfed with her own reversed pollen. All S1s are feminised; most feminised seed is a cross of two different females.
- Regular seed: male × female, about half males.
- Autoflower: a flowering trait, independent of feminisation.
Myth check
Herms in feminised seed are mainly breeder error, not "what fem seed does". See feminised seed and sex reversal and Mythbusters.
A male flower that carries stamens (anthers on filaments) and no functional pistil; in cannabis, five drooping sepals around five pollen-shedding anthers.Sex reversal is chemically inducing a genetically female cannabis plant to grow fertile male flowers, so its pollen can make feminised seed; silver thiosulfate is the standard agent.STS (silver thiosulfate) is a silver compound sprayed on female cannabis to block ethylene action and induce fertile male flowers, the standard method for making feminised seed.A chromosome is one long DNA molecule packaged with proteins that carries many genes; cannabis normally has 10 pairs, nine autosome pairs plus an X/Y sex pair.In cannabis growing, a plant (usually female) that develops both pistillate and staminate flowers or anthers; botanists call it intersex or monoecious expression.S1 is seed from a plant pollinated with its own pollen; every S1 seed is female and a new genotype, not a copy of the parent.Selfing is pollinating a plant with its own pollen, in cannabis usually by reversing part of a female to make pollen; it is the most intense form of inbreeding.A day-neutral cannabis plant that starts flowering by age, usually a few weeks after germination, regardless of light schedule; the trait is mainly recessive.Regular seed comes from a normal cross of a female and a male, so it produces roughly half female and half male plants.Cannabis uses an XY sex determination system: females carry two X chromosomes (XX) and males an X and a Y (XY), so regular seed is roughly half male.
