# Hermaphrodite cannabis (bananas and nanners): what to do

> Hermaphroditic flowers are anthers (often banana-shaped) or pollen sacs forming on a female plant. Cannabis is a dioecious species, and a well-bred female should stay female; herm-prone plants are mainly the product of bad breeding (repeated selfing, careless feminising, untested 'pollen chucker' seed). Stress such as light leaks or heat reveals that weakness rather than causing it in sound genetics. Fix the environment, remove the plant if it sheds pollen, and never keep it as a mother or breed from it.

- Canonical: https://genetixbay.com/knowledge/diagnosis/hermaphrodites.html
- Category: Diagnosis · Level: Intermediate
- Evidence: Supported · Status: Draft: awaiting expert review (some figures are being checked)
- Stage: Transition, Flower, Ripening · Systems: Any system
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Questions and answers

**My cannabis plant is growing bananas: what do I do?** If a cannabis plant grows a few closed bananas (bare anthers) in late flower, pluck them carefully with tweezers, lightly mist the area, and inspect every 2 to 3 days. If it has many anthers, pollen-sac clusters or is shedding pollen, bag it and remove it from the room. Then fix [light leaks](https://genetixbay.com/knowledge/glossary/light-leak.md) or heat, and never keep the plant as a mother.

**Why did my cannabis plant turn hermaphrodite?** A cannabis plant turns hermaphrodite mainly because its genetics are herm-prone, usually from repeated selfing, careless feminising or untested seed from people who never cull. Stress such as light leaks, a skipped dark period or heat then reveals that weakness. If one plant hermed while others in identical conditions stayed female, the environment exposed it, but the genetics are the real problem.

**Are cannabis hermaphrodites genetic or caused by stress?** Cannabis hermaphrodites are mainly genetic, with stress acting as the trigger that reveals susceptible plants. Research links interrupted darkness, altered photoperiods, low temperatures and chemicals to [male flowers](https://genetixbay.com/knowledge/glossary/staminate-flower.md) on females, yet the same light leak leaves a stable clone beside it untouched. Hemp studies show sex expression is heritable and responds to selection, which is why GenetixBay treats herm-prone lines as breeder error.

**Can light leaks cause cannabis hermaphrodites?** Light leaks can trigger hermaphrodite flowers on susceptible cannabis plants, since research links interrupted darkness to sex reversal, but they do not make a well-bred female herm. Keep the 12-hour dark period fully light-tight: sit in the room for about 10 minutes with eyes adjusted and look for gaps in seals, vents and equipment indicator LEDs. Check timer and controller logs too.

**Are nanners in late cannabis flower a problem?** Nanners in late cannabis flower are a real problem: they are staminate flowers producing pollen that looked normal and germinated 10 to 30% in vitro in a controlled study. That pollen can seed buds, lowering quality, and research shows hermaphrodite pollen produced all-female seed that carries the same tendency. Treat them as a genetic defect to record and report, not a harmless finishing quirk.

**Will a hermaphrodite pollinate my whole cannabis room?** A hermaphrodite that opens and sheds pollen can pollinate other flowering cannabis plants, and seeded buds are lower in quality because seed formation diverts resources. Research found seeded inflorescences held 22 to 48 seeds. Bag the plant before moving it to contain pollen, remove it from the room, and inspect every plant for new anthers and seeds over the following 7 to 14 days.

**Should I keep or breed a cannabis plant that hermed?** A cannabis plant that hermed should not be kept as a mother, cloned, reversed or used for breeding, even if it is your best plant. Research shows hermaphrodite pollen gave only female progeny, so its seed is feminised seed carrying the same weakness. The GenetixBay breeder standard is to cull it, record the event and tell the breeder of the line.

**Are late-flower bananas normal on cannabis?** Late-flower bananas are not normal on cannabis; the claim that they are is a myth. A banana is a staminate flower reduced to its anthers, forming inside a female bud, which is intersex expression. Cannabis is a dioecious species with an [XY system](https://genetixbay.com/knowledge/glossary/xy-sex-determination.md), and a well-bred female stays female even through a long finish. GenetixBay holds this as a firm house position.

**Is it OK to have a few nanners at the end of cannabis flower?** A few closed nanners in the last days of cannabis flower can be managed to finish the run, but the plant is still a herm. Pluck them with tweezers and monitor closely, then record it, take no cuts and make no seed from it. On GenetixBay, a line whose tester grows herm above 2% does not qualify for [Bay Lines](https://genetixbay.com/knowledge/glossary/bay-lines.md), [the Seed Club](https://genetixbay.com/knowledge/glossary/seed-club.md) or featuring.

**Short answer.** A "hermie" is a female plant that also makes male flower parts: small yellow-green, banana-shaped anthers poking out among the pistils, or full pollen-sac clusters. Cannabis is a dioecious species with a long-established XY system [2][3]; a well-bred female stays female. Herm-prone plants are **mainly breeder error**: lines built on repeated selfing, careless feminising, or untested seed from "[pollen chuckers](https://genetixbay.com/knowledge/glossary/pollen-chucker.md)". Stress (light leaks, heat, a missed dark period) reveals that weakness; it doesn't create it in sound genetics. Fix the trigger, pluck a few closed anthers in late flower or remove the plant if it's shedding pollen, and **never** keep it as a mother or breed from it.

> **Breeder's standard.** A plant that throws male flowers under normal room conditions is culled from the breeding programme, along with any clone of it. It is never used as a pollen donor, a seed mother or a reversal donor. Its herm rate is recorded and disclosed with any seed from the same line. GenetixBay treats this as an ethics standard, not a preference: see [record-keeping and naming ethics](https://genetixbay.com/knowledge/breeding/record-keeping-naming-ethics.md).

## What's happening

Cannabis has been a dioecious plant, with separate males and females, for as long as people have grown it. Its sex chromosomes are old and the Y is strongly degenerated [2][3]. Separate sexes are the species' stable, normal state. An intersex female is an unwanted outlier, not the plant "doing what plants do".

Drug-type cannabis has been recorded as dioecious throughout its history: growers and writers have always distinguished male from female plants, and ancient Chinese texts already used separate names for male and female hemp [5]. [Monoecious hemp](https://genetixbay.com/knowledge/glossary/monoecious.md), with both sexes on one plant, exists only because 20th-century fibre breeders selected for it on purpose; it is not the norm and says nothing about how drug-type cannabis behaves. Selfing, too, was historically an emergency measure, used to save a line when no male was left, not a trait anyone wanted.

Why do some modern plants herm so readily, then? The GenetixBay breeder position, drawn from decades of growing and breeding:

- **Repeated selfing (S1 on S1).** Selfing a plant that has already shown intersex flowers concentrates whatever makes it do so. See [S1s and selfing](https://genetixbay.com/knowledge/breeding/s1-selfing.md).
- **Careless feminising.** Reversing a female that hasn't been proven stable across several runs, or collecting pollen from a stress herm instead of a controlled reversal, puts that tendency into every seed. See [feminised seed and sex reversal](https://genetixbay.com/knowledge/breeding/feminised-seed-sex-reversal.md).
- **"Pollen chuckers".** People who cross whatever is in the room and release the seed without growing out and culling. Unstable genetics then spread widely under popular names.

What the research shows fits that picture. Punja and Holmes characterised hermaphroditism in commercial indoor cannabis: anthers formed in clusters in bract tissue next to the stigmas, from about week 4 of flower through harvest; anther and pollen looked like those of normal males; pollen germinated 10–30% in vitro; seeded inflorescences held 22–48 seeds; whole inflorescences converting to anthers was rare (~2 in 1000 plants) [1]. They saw this on roughly 5–10% of plants across three cultivars in one commercial facility [1]. We read that rate as evidence of poor genetics in that operation's cultivars, not as normal cannabis behaviour. The founder has grown thousands of cultivars and doesn't see it in older lineages, only in the recent wave of low-quality releases. They cite older work linking male flowers to applied chemicals ([gibberellins](https://genetixbay.com/knowledge/glossary/gibberellin.md), silver compounds, cobalt chloride) and to stresses such as altered photoperiods, interrupted darkness and low temperatures [1]. We read that as stress *revealing* susceptible genetics. The same light leak that makes one clone herm leaves a stable clone beside it untouched. Seed from hermaphrodite pollen gave only female progeny in the strains tested [1], which is why a herm in the room passes its tendency straight into the next generation of "feminised" seed.

## Late-flower "bananas" are not normal

> **House position (firm): late nanners are a herm, and they're unwanted.** You'll hear it in every grow forum: "a few bananas at the end are normal, the plant is just trying to seed itself." It isn't normal. A female that grows anthers in its buds late in flower is expressing male flowers: it's intersex, a herm. That holds even if it's the best plant you've ever grown, the loudest gas in the room, the keeper you've hunted for years. It's a sign of poor genetics, from bad breeding or pollen-chucking behaviour, and base lines that are prone to it got that way through bad practice early on. You can sometimes breed it out of a line with patient selection, but usually that isn't the approach: **cull it, don't keep it as a mother, and don't breed from it.** The founder will die on this hill.

**What a late banana actually is.** The yellow "banana" is a staminate flower reduced to its anthers, forming inside a pistillate inflorescence. Punja and Holmes found these anthers in clusters in bract tissue next to the stigmas, from about week 4 of flower right through to harvest, with pollen that looked like a normal male's and germinated 10–30 % in vitro [1]. Late timing doesn't make it a different thing. It's the same intersex expression, showing up when the plant is under the most pressure.

**Why we call it genetics, with the evidence:**

- **Sex expression is heritable.** In monoecious hemp, how much male and female flowering a plant shows varies between cultivars and has a genetic basis [7]; genome-wide work has mapped loci associated with sex expression [8]. That's hemp, not drug-type cannabis, but it's the same species and the same flowering machinery.
- **It responds to selection.** Monoecious hemp exists because 20th-century fibre breeders selected for plants that make both sexes [10]. If selection can push the species towards both sexes on one plant, careless breeding can drift a line that way, and careful breeding can keep it female.
- **Herm pollen makes herm-prone "feminised" seed.** Seed from hermaphrodite pollen gave only female progeny in the strains tested [1], and controlled reversal with silver does the same thing on purpose [9]. A late banana that drops pollen in your room has just made feminised seed carrying its own tendency. Selfing such plants, or reversing them for "fem" seed, is how the trait spreads through the market. See [S1s and selfing](https://genetixbay.com/knowledge/breeding/s1-selfing.md) and [feminised seed and sex reversal](https://genetixbay.com/knowledge/breeding/feminised-seed-sex-reversal.md).
- **Stable plants don't do it under the same conditions.** In one facility, intersex flowers turned up on roughly 5–10 % of plants [1]; we read that as a sign of poor genetics in those cultivars, not as a normal rate. Under the same lights, the same feed and the same long finish, a well-bred female stays female.

**The honest part.** Research does show that stress can trigger intersex flowers: interrupted darkness, altered photoperiods, low temperatures, and chemicals such as silver compounds or gibberellins have all been linked to male flowers on females [1][9]. Late flower is a stressful time, especially if a plant is run past its window. We don't deny that. We read it the way a breeder does: **stress reveals susceptible genetics; it doesn't make a stable plant herm.** The light leak or the extra two weeks was the test, and the plant failed it. What hasn't been published is a heritability estimate for intersex tendency in drug-type cannabis specifically, so the genetic case rests on the hemp work, the breeding history and long breeder experience.

**What to do.** If it's a handful of closed anthers in the last days and you're finishing the run, pluck and monitor. But record it, don't take cuts from it, don't make seed with it, and tell the breeder. On GenetixBay, a line whose tester grows herm above 2 % doesn't qualify for Bay Lines, the Seed Club or featuring. See [breeders vs pollen chuckers](https://genetixbay.com/knowledge/breeding/breeders-vs-pollen-chuckers.md).

## How to recognise it

| What you see | What it is | Urgency |
|---|---|---|
| A few yellow "bananas" (bare anthers) poking from buds, late flower | Hermaphroditic anthers | Medium: pluck, monitor, flag the genetics |
| Clusters of round, pale green balls on stalks at nodes (pollen sacs) | Male flowers on a female | High: remove plant or branch |
| [Pollen dust](https://genetixbay.com/knowledge/glossary/pollen.md) on leaves below | Pollen release | High: isolate immediately |
| Fresh calyx spires, no anthers | Foxtailing | See [foxtails](https://genetixbay.com/knowledge/diagnosis/foxtails.md) |
| Seeds in buds at harvest | Pollination happened weeks ago | Find the source |

## Numbers that matter

| Parameter | Target | Notes |
|---|---|---|
| Dark period in flower | 12 h, uninterrupted, light-tight | Grower practice; light interruptions linked to sex reversal [1] |
| Light leak test | no visible light after ~10 min eyes adjusted in the dark | Grower practice |
| [Canopy temperature](https://genetixbay.com/knowledge/glossary/leaf-temperature.md) | < ~30 °C (86 °F) | [Heat stress](https://genetixbay.com/knowledge/glossary/heat-stress.md) [6]; grower practice links heat to hermies in susceptible plants |
| Typical onset | ~week 4 of flower onwards | [1] |
| Observed incidence | ~5–10% of plants, 3 commercial cultivars, one facility | [1]; not a "normal" rate for well-bred lines |
| Pollen germination | 10–30% in vitro | [1] |
| Runs a mother must stay clean before breeding | at least 2 | GenetixBay breeder's standard |

## What to check first

1. **Light leaks.** Sit in the room or tent in the dark for 10 minutes. Check door seals, LEDs on equipment, vents.
2. **Timer and controller logs.** A night with the light on, or a skipped dark period, is the classic trigger for a susceptible plant.
3. **Heat and [light stress](https://genetixbay.com/knowledge/glossary/light-stress.md)** at the tops.
4. **Other stresses:** severe root problems, pests, drought, extreme pruning in flower.
5. **Plant history.** Where did the seed come from? Is it an S1 of an S1, a feminised line from an unproven donor, or a "freebie" from someone who doesn't cull? Has this clone done it before?
6. **The neighbours.** If one plant hermed and the rest of the room under identical conditions did not, the environment exposed it; the genetics are the problem.

## How to fix it

- **Isolated bananas, late flower, not open:** pluck them carefully with tweezers, mist the area lightly with water to deactivate any loose pollen (grower practice), and inspect every 2–3 days.
- **Many anthers, male flower clusters, or pollen shedding:** remove the plant from the room (bag it first to contain pollen). Harvest early if it is near maturity.
- **Fix the trigger:** seal light leaks, replace faulty timers, correct heat stress. That protects the rest of the room.
- **Fix the genetics:** cull the clone; don't keep it as a mother. Record the event (week, trigger if any, photos) in your journal. If it came from a seed line, tell the breeder and note it publicly on the line record.
- **Seeded buds:** quality is reduced; seed formation diverts resources [1]. Don't save or sell the seed.

## How to confirm it worked

- No new anthers on any plant over the next 7–14 days of inspection (hand lens, focus on bud interiors and node sites).
- At harvest, few or no seeds.
- Next run, with the trigger fixed and the culprit gone, a clean room.

## Common mistakes

- Treating hermies as normal cannabis behaviour. They are not; they are a defect to breed out.
- Calling late-flower bananas "normal" and keeping the plant because it smokes well.
- Blaming only the light leak, and keeping the clone. The leak was the test; the clone failed it.
- Saving "free feminised seed" from a hermed bud. Every seed carries the tendency.
- Missing light leaks from equipment indicator LEDs.
- Confusing foxtails with anthers.

## Evidence

- Cannabis is dioecious with an XY system: *Established* [2][3].
- Morphology, timing, pollen viability and progeny sex of intersex flowers: *Established* by one controlled study [1]. Its 5–10% incidence describes one facility's cultivars and is read here as a sign of poor genetics, not a normal rate.
- Drug-type cannabis recorded as dioecious through history; monoecious hemp a deliberate modern breeding product: *Established* [5].
- Stress and chemical triggers: *Supported* by older literature cited in [1]; specific thresholds are *Grower practice*.
- Herm-prone lines arise mainly from breeding practice (repeated selfing, careless feminising, no culling): GenetixBay house position, grounded in long breeder experience. Selfing was historically an emergency measure to save a line, not a desirable trait. Rule: cull herm-prone plants and don't breed from them.
- Sex expression having a genetic basis and responding to selection: *Supported* in hemp [7][8], and by the deliberate breeding of monoecious hemp [10].
- "Late-flower bananas are normal": *Myth* (house position). They are intersex flowers [1]; stress can trigger them, which we read as stress revealing susceptible genetics.

## 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
2. Divashuk MG, Alexandrov OS, Razumova OV, Kirov IV, Karlov GI. 2014. Molecular cytogenetic characterization of the dioecious Cannabis sativa with an XY chromosome sex determination system. PLoS ONE 9(1):e85118. https://doi.org/10.1371/journal.pone.0085118
3. Prentout D, Razumova O, Rhone B, et al. 2020. An efficient RNA-seq-based segregation analysis identifies the sex chromosomes of Cannabis sativa. Genome Research 30(2):164-172. https://doi.org/10.1101/gr.251207.119
4. Punja ZK, et al., 2019. Pathogens and Molds Affecting Production and Quality of Cannabis sativa L. Frontiers in Plant Science 10:1120. https://doi.org/10.3389/fpls.2019.01120
5. Clarke RC, Merlin MD. 2013. Cannabis: Evolution and Ethnobotany. University of California Press. https://doi.org/10.1525/9780520954571
6. Chandra S, Lata H, Khan IA, ElSohly MA., 2008. Physiology and Molecular Biology of Plants 14(4):299-306. https://doi.org/10.1007/s12298-008-0027-x
7. Faux AM, Berhin A, Dauguet N, Bertin P. 2014. Sex chromosomes and quantitative sex expression in monoecious hemp (Cannabis sativa L.). Euphytica 196(2):183-197. https://doi.org/10.1007/s10681-013-1023-y
8. Petit J, Salentijn EMJ, Paulo MJ, Denneboom C, Trindade LM. 2020. Genetic architecture of flowering time and sex determination in hemp (Cannabis sativa L.): a genome-wide association study. Frontiers in Plant Science 11:569958. https://doi.org/10.3389/fpls.2020.569958
9. 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
10. Small E. 2015. Evolution and classification of Cannabis sativa (marijuana, hemp) in relation to human utilization. The Botanical Review 81:189-294. https://doi.org/10.1007/s12229-015-9157-3