Selfing
A breeding technique that forces a female cannabis plant to pollinate itself, producing all-female (feminized) seeds.
Selfing is how nearly every 'feminized seed' on the market gets made. It's a legitimate technique, not a gimmick — but it's also not magic. S1 seeds inherit only one plant's genetics, so they express recessive traits, hidden weaknesses, and reduced vigor more often than F1 hybrid crosses. If someone claims their feminized line is 'more stable than regular seeds,' be skeptical. Stability comes from generations of selection, not from the selfing process itself.
Definition
Selfing (pronounced SELF-ing) is the process of pollinating a female cannabis plant with pollen derived from that same plant, or from a genetically identical clone of it. Because cannabis is normally dioecious — meaning male and female flowers grow on separate plants — selfing requires chemically forcing a female to produce viable pollen. The resulting seeds are called S1 (selfed first generation) and are genetically feminized: they lack a Y chromosome contribution and grow into female plants at very high rates Strong evidence.
How it's done
The most common method uses silver thiosulfate (STS), a solution that inhibits ethylene signaling in the plant. Sprayed on a female during early flowering, STS induces the plant to develop staminate (male) flowers that produce viable, XX-only pollen [1] Strong evidence. Colloidal silver works via a similar mechanism and is popular among hobby breeders [2]. Gibberellic acid can also induce male flowers but is less reliable Weak / limited.
The pollen from these induced male flowers is then collected and used to pollinate either:
- The same plant (true selfing), or
- A clone of the same plant (still considered selfing), or
- A different female plant (this is how most commercial 'feminized' crosses are made, and technically not selfing — it's a feminized cross).
What selfing does
Selfing reliably produces seeds that grow into female plants — typically 99%+ female when the STS process is done correctly [1] Strong evidence. This is valuable for growers who don't want to cull males and for seed companies serving that market. It also lets breeders expose recessive traits hidden in a mother plant. Because both 'parents' are the same genome, any recessive allele has a 25% chance of appearing homozygous in the S1 offspring — useful for finding rare phenotypes or purging deleterious alleles [3] Strong evidence.
What selfing doesn't do
Selfing does not create clones in seed form. S1 seeds are not genetic copies of the mother; they are a segregating population, and phenotypes can vary noticeably from the original plant [3] Strong evidence. Selfing also does not inherently produce more stable or higher-quality plants than regular (dioecious) seed breeding. In fact, single-generation selfing often produces inbreeding depression: reduced vigor, smaller yields, and higher rates of hermaphroditism in the offspring compared to well-bred F1 hybrids [4] Weak / limited.
Selfing also doesn't guarantee non-hermaphroditic offspring. If the mother plant carries genetic predisposition to intersex expression under stress, her S1 offspring will too — and there's folklore, unsupported by strong evidence, claiming feminized seeds are inherently more prone to herming Disputed.
Used in articles about
Selfing comes up when discussing Feminized Seeds, Silver Thiosulfate (STS), Hermaphroditism in Cannabis, and Cannabis Breeding. It's distinct from a feminized cross (pollen from a reversed female applied to a different female) and from a backcross (BX), which uses conventional male pollen from a related line.
Sources
- Peer-reviewed Lubell, J. D., & Brand, M. H. (2018). Foliar sprays of silver thiosulfate produce male flowers on female hemp plants. HortTechnology, 28(6), 743-747.
- Peer-reviewed Ram, H. Y. M., & Sett, R. (1982). Induction of fertile male flowers in genetically female Cannabis sativa plants by silver nitrate and silver thiosulphate anionic complex. Theoretical and Applied Genetics, 62(4), 369-375.
- Book Clarke, R. C., & Merlin, M. D. (2013). Cannabis: Evolution and Ethnobotany. University of California Press.
- Peer-reviewed Charlesworth, D., & Willis, J. H. (2009). The genetics of inbreeding depression. Nature Reviews Genetics, 10(11), 783-796.
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