Short answer. Sex a cannabis plant by its first solitary flowers at the nodes, usually visible about 4–6 weeks from seed under long days. A female shows a teardrop-shaped bract with two white stigmas; a male shows a small round ball on a short stalk, with no hairs. A hermaphrodite grows both, or pushes banana-shaped anthers (nanners) out of its buds. Check with a 30–60x loupe under white light.
House position: herms are mainly breeder error. Cannabis is dioecious and has kept separate sexes stably for thousands of years [2][5][6]. Herm-prone lines mostly come from bad breeding: repeated selfing, careless feminising and pollen chuckers spreading untested seed. Stress can trigger intersex flowers, but that is stress revealing susceptible genetics, not normal behaviour. Late-flower bananas are not normal. A banana is a herm, however good the plant smells. Cull it; never breed from it.
What do you need to sex your plants?
Sexing needs good eyes more than gear:
- [ ] A 30–60x jeweller's loupe or phone macro lens
- [ ] A white torch or headlamp (grow-light colours hide detail), used only during lights-on
- [ ] Plant labels or tags, and your grow journal
- [ ] Clean scissors and a bin bag for removing males and herms
- [ ] Optional: a small separate space if you want to keep a male for breeding
- [ ] Optional: a DNA sex-test kit (leaf punch) for regular seed
What do male and female flowers look like?
The first flowers form singly in the leaf axils at the nodes, driven by plant age and internal signals, not the light schedule [1]. That's why they appear in veg.
| Feature | Female | Male | Hermaphrodite |
|---|---|---|---|
| First flowers at the nodes | Teardrop bract with 2 stigmas (white hairs) | Round ball on a short stalk, no hairs | Both kinds on one plant |
| When visible | ~4–6 weeks from seed under long days | Same, often a few days earlier | Usually after the flip, sometimes late flower |
| After the flip | Clusters of white pistils at branch tips | Grape-like clusters of balls that open into pollen sacs in ~2–3 weeks | Pistil clusters plus male balls, or single bananas in buds |
| Risk | None | Sheds pollen and seeds the room | Sheds pollen; seeds carry the herm tendency |
Don't confuse stipules, the small pointed leafy spurs either side of each node, with flowers. Stipules are thin and green with no bract or stigma.
How do you sex and check your plants, step by step?
- Know your seed type. Regular seed gives roughly half males; feminised seed should be nearly all female; clones are the sex of their mother (seed types).
- Start checking at week 4 from seed. Every 2–3 days, look at the top 3–4 nodes of the main stem with a loupe, during lights-on.
- Wait for a clear flower. One ambiguous bump isn't enough. Wait until you see two stigmas (female) or a definite stalked ball (male).
- Tag every plant with its sex and the date you confirmed it. Log it.
- Remove males from the flower room before their balls open. Male flower clusters usually open about 2–3 weeks after they form; in practice, decide within 1–2 weeks of the flip. Bag the plant before moving it.
- Keep checking after the flip. Days 1–21 after the flip are the main window for herm flowers at the nodes. Look at the lower and inner nodes as well as the tops.
- Scan buds weekly from week 4 of flower to harvest for bananas: single, yellow-green, curved anthers poking out between the calyxes.
- If you find one or two bananas, check for a cause: a light leak, heat above 30 °C, a damaged branch, a missed feed. Fix it, pluck the bananas with tweezers, and check again every day.
- If bananas keep coming, or any open pollen sacs, cull the plant or harvest it early, bagging it first. Wipe surfaces and change clothes before touching other plants.
- Never keep a herm as a mother and never breed from it. Herm tendency passes straight on: seed from a female's own male flowers is almost all female and inherits the weakness [3].
- Report it in your journal and on the line's GenetixBay record, with photos and the week. That is how herm-prone lines get exposed.
Do herms come from stress or bad genetics?
Herms come mainly from genetics, and stress is what reveals them. The GenetixBay breeder position: drug-type cannabis has been recorded as dioecious throughout history [5][6], it carries an XY sex-determination system [2], and herm-prone populations mostly come from repeated selfing (S1 on S1), careless feminising and untested pollen-chucker releases (breeders vs pollen chuckers).
Research supports the observation that intersex flowers do occur in commercial crops: Punja and Holmes documented them and showed seeds from them were mostly female [3]. GenetixBay interprets those numbers as a sign of poor genetics, not normal cannabis: 5–10 % herms in a commercial room means bad stock. Female plants can also be made to grow male flowers on purpose with silver thiosulfate sprays [7], which is how feminised seed is made, and why careless feminising spreads the trait. The founder has grown thousands of cultivars and doesn't see herms in older lineages, only in the recent wave of low-quality releases.
What is GenetixBay's herm standard?
GenetixBay holds lines to a measured herm standard. To be featured, a line needs a 10-plant screening grow with zero herms; to be Verified as a Bay Line or for the Seed Club, it needs about 150 or more community-grown tester plants with a confirmed herm rate under 2 % (herm threshold). Your journal entry, herm or no herm, counts towards that record.
Are males worth keeping?
Yes. Males are a necessity, not waste: every seed has a father, and half of a line's quality comes from him. GenetixBay encourages and rewards good males through the Stud Book, its showcase of documented males with selection journals and sire credits. If you're growing for flower, move males out before they open. If you want to breed, keep your best male in a separate space and collect pollen deliberately (pollen collection, male selection).
How will you know you've got it right?
You'll know your sexing works when your flower room stays seedless:
- Every plant is tagged with its sex and confirmation date before day 14 after the flip.
- Female nodes show paired white stigmas; pistil clusters form at the tips about 10–14 days after the flip.
- No male flower balls appear at nodes during the first three weeks of flower.
- Weekly bud scans from week 4 find no bananas.
- At harvest and trim, you find no seeds, or only an odd one.
- Your journal records any herm with the week, the trigger you checked, and what you did.
What mistakes do beginners make with sex and herms?
- Calling sex from stipules or a single ambiguous bump.
- Looking under coloured grow lights, which hide pistils and anthers.
- Keeping a male "to see what happens" in the flower room. One opened cluster can seed every plant.
- Calling bananas normal because a forum said so. They are a herm.
- Breeding from a herm or keeping it as a mother because it smells great.
- Ignoring light leaks in the dark period; they expose susceptible plants.
- Moving a male or herm unbagged, spreading pollen through the room.
- Not reporting it. A herm record helps every grower who buys that line next.
Evidence
- Solitary flowers form by age, not photoperiod: Established [1].
- XY sex determination and dioecy: Established [2]. Validated DNA sex markers: Established [4].
- Intersex flowers occur in commercial drug-type crops and produce mostly female seed: Supported [3]; GenetixBay interprets high rates as poor genetics.
- Herms mainly from breeding practice, stress revealing susceptibility: house position, supported by historical dioecy [5][6] and induced-maleness research [7].
- Late-flower bananas not normal: house position.
