# Herm-prone

> Herm-prone describes a line whose plants often produce intersex flowers; GenetixBay treats this as a breeding fault and a reason not to breed from it.

- Canonical: https://genetixbay.com/knowledge/glossary/herm-prone.html
- Also written: herm prone, hermy, hermie-prone, herm tendency, herm-y
- Glossary category: Grower slang and culture · Evidence: Supported
- 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"

Herm-prone describes a cultivar or seed line in which a noticeable share of plants develop [male flowers](https://genetixbay.com/knowledge/glossary/staminate-flower.md) or bare anthers alongside [female flowers](https://genetixbay.com/knowledge/glossary/pistillate-flower.md). It is a property of the genetics, revealed more often under stress such as [light leaks](https://genetixbay.com/knowledge/glossary/light-leak.md), heat or late harvest.

## In practice

A grower who sees [nanners](https://genetixbay.com/knowledge/glossary/nanners.md) on 3 of 10 plants from one pack, in a tent where another line stayed clean, has good reason to call that pack herm-prone. On GenetixBay every line publishes a [herm rate](https://genetixbay.com/knowledge/glossary/herm-threshold.md) from tester grows; any [herm](https://genetixbay.com/knowledge/glossary/hermaphrodite.md) in the 10-plant screening grow, or a pooled rate above 2%, keeps a line out of featuring and the community programmes (see [herm threshold](https://genetixbay.com/knowledge/glossary/herm-threshold.md)). Log every intersex plant against its batch record so the rate is real data, not anecdote.

## Don't confuse with

- **Stress-induced herm**: an argument, not a separate category. Almost any plant can be forced with extreme stress; the question is how easily. Lines that herm under ordinary indoor conditions are herm-prone.
- **Monoecious hemp**: bred on purpose to carry both flower types; not the norm for cannabis.

## Myth check

"All cannabis herms under stress, so it doesn't matter." GenetixBay house position: herm-prone lines are **mainly breeder error**: repeated selfing ([S1](https://genetixbay.com/knowledge/glossary/s1.md) on S1), careless feminising, and [pollen chuckers](https://genetixbay.com/knowledge/glossary/pollen-chucker.md) spreading unstable genetics. 5-10% herms in a commercial room means poor genetics, not normal cannabis. Cull, don't breed. See [hermaphrodites](https://genetixbay.com/knowledge/diagnosis/hermaphrodites.md) and [Mythbusters](https://genetixbay.com/knowledge/mythbusters.md).

## Related terms

[Nanners](https://genetixbay.com/knowledge/glossary/nanners.md), [Hermaphrodite](https://genetixbay.com/knowledge/glossary/hermaphrodite.md), [Herm threshold](https://genetixbay.com/knowledge/glossary/herm-threshold.md), [Pollen chucker](https://genetixbay.com/knowledge/glossary/pollen-chucker.md), [S1](https://genetixbay.com/knowledge/glossary/s1.md)

## Read more

- [Hermaphrodite cannabis (bananas and nanners): what to do](https://genetixbay.com/knowledge/diagnosis/hermaphrodites.md)
- [S1s and selfing: what happens when a plant pollinates itself](https://genetixbay.com/knowledge/breeding/s1-selfing.md)

## Sources

1. Punja ZK, Holmes JE. 2020. Hermaphroditism in marijuana (Cannabis sativa L.) inflorescences: impact on floral morphology, seed formation, progeny sex ratios, and genetic variation. Frontiers in Plant Science 11:718. https://doi.org/10.3389/fpls.2020.00718