# Sex reversal

> 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.

- Canonical: https://genetixbay.com/knowledge/glossary/sex-reversal.html
- Also written: reversal, reversed female, reversed plant, colloidal silver, masculinising, masculinizing
- Glossary category: Genetics and breeding · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Sex reversal is treating a genetically female (XX) plant so that it forms [male flowers](https://genetixbay.com/knowledge/glossary/staminate-flower.md) that shed fertile pollen. Silver ions block the plant's response to [ethylene](https://genetixbay.com/knowledge/glossary/ethylene.md), a hormone involved in [female flower](https://genetixbay.com/knowledge/glossary/pistillate-flower.md) development, which lets male flowers form instead (Ram and Sett 1982). [Silver thiosulfate](https://genetixbay.com/knowledge/glossary/sts.md) (STS) is the standard agent; colloidal silver works on the same principle but is less consistent. Both are generic chemical names.

## In practice

Breeders reverse one female, or a branch of her, then use the pollen on other females (a [feminised](https://genetixbay.com/knowledge/glossary/feminised-seed.md) cross) or on the same plant (an [S1](https://genetixbay.com/knowledge/glossary/s1.md)). The reversed plant's own flowers are not usable bud. Silver compounds are toxic, so treated material is kept out of consumption and handled with gloves; the treatment details are in the main article.

"Rodelization" is a grower term for letting a female run past ripeness in the hope she throws pollen on her own. That deliberately selects for plants that break down into [herms](https://genetixbay.com/knowledge/glossary/hermaphrodite.md), and is not good breeding.

## Don't confuse with

- **Hermaphrodite**: a plant that makes both flower types on its own, from genetics or stress. Reversal is deliberate and controlled.
- **Reciprocal cross**: swapping parents' roles, a different meaning of "reversed".

## Myth check

Only reverse females that have stayed fully female over several runs. Reversing a plant that already herms passes that weakness on. See [feminised seed and sex reversal](https://genetixbay.com/knowledge/breeding/feminised-seed-sex-reversal.md).

## Related terms

[STS](https://genetixbay.com/knowledge/glossary/sts.md), [Feminised seed](https://genetixbay.com/knowledge/glossary/feminised-seed.md), [S1](https://genetixbay.com/knowledge/glossary/s1.md), [Selfing](https://genetixbay.com/knowledge/glossary/selfing.md), [XY sex determination](https://genetixbay.com/knowledge/glossary/xy-sex-determination.md)

## Read more

- [Feminised seed and sex reversal: methods, with safety notes](https://genetixbay.com/knowledge/breeding/feminised-seed-sex-reversal.md)

## Sources

1. Ram HYM, 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 62:369-375. https://doi.org/10.1007/BF00275107
2. Lubell JD, Brand MH. 2018. Foliar sprays of silver thiosulfate produce male flowers on female hemp plants. HortTechnology 28(6):743-747. https://doi.org/10.21273/HORTTECH04188-18
3. Flajšman M, Slapnik M, Murovec J. 2021. Production of feminized seeds of high CBD Cannabis sativa L. by manipulation of sex expression and its application to breeding. Frontiers in Plant Science 12:718092. https://doi.org/10.3389/fpls.2021.718092