# When do cannabis plants show their sex?

> Cannabis plants usually show their sex about 4–6 weeks from seed under long days, when single preflowers form at the nodes; research found the first pair around the 7th node. You need a 30–60x loupe. Males often show first. For an earlier answer, flower a cutting on 12/12 (about 1–2 weeks) or use a DNA sex test from the first true leaves.

- Canonical: https://genetixbay.com/knowledge/answers/when-do-plants-show-sex.html
- Topic: Basics · Type: Numbers
- Evidence: Supported · Status: Draft: awaiting expert review
- Full article: [Male, female and hermaphrodite cannabis: how sex works](https://genetixbay.com/knowledge/basics/sex-male-female-hermaphrodite.md)
- Also asked as: When can you tell if a plant is male? | How long until preflowers show? | When do preflowers appear? | How to sex cannabis plants early
- 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)"

## Short answer

Cannabis plants usually show their sex about 4–6 weeks from seed under long days, as single [preflowers](https://genetixbay.com/knowledge/glossary/pre-flower.md) at the nodes. Look with a 30–60x [loupe](https://genetixbay.com/knowledge/glossary/jewelers-loupe.md). Males often show a little earlier. *Supported* by research on preflower timing; the week range is *Grower practice*.

## Why

Preflowers come with age. Cannabis [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) pass from a juvenile to an adult stage on their own, then form single flowers at the nodes whatever the light schedule; in one cultivar the first pair formed at the 7th node [1]. Solitary flowers are age-dependent and not induced by [photoperiod](https://genetixbay.com/knowledge/glossary/photoperiod.md) [2].

Sex is genetic. Cannabis is [dioecious](https://genetixbay.com/knowledge/glossary/dioecious.md) with an [XY system](https://genetixbay.com/knowledge/glossary/xy-sex-determination.md): females XX, males XY [4]. A preflower simply shows which one the plant is.

DNA tests read the [chromosomes](https://genetixbay.com/knowledge/glossary/chromosome.md) directly. Validated Y-linked markers identify males from seedling leaves [3], weeks before any flower shows.

## The numbers

| Method | When you get an answer | Cost |
|---|---|---|
| Watch preflowers | ~4–6 weeks from seed (from ~7th node) | Free, plus a loupe |
| Flower a labelled cutting on [12/12](https://genetixbay.com/knowledge/glossary/12-12.md) | ~1–2 weeks after the cut goes into long nights | Space and time |
| PCR or PACE [DNA test](https://genetixbay.com/knowledge/glossary/genotyping.md) | From the [first true leaves](https://genetixbay.com/knowledge/glossary/true-leaves.md) | Lab fee |
| [Autoflower](https://genetixbay.com/knowledge/glossary/autoflower.md) | ~week 3–5, as it starts flowering | Free |

| Sign | Female | Male |
|---|---|---|
| Shape | Teardrop [bract](https://genetixbay.com/knowledge/glossary/bract.md) | Round ball on a short stalk |
| [Hairs](https://genetixbay.com/knowledge/glossary/pistil.md) | Two [stigmas](https://genetixbay.com/knowledge/glossary/stigma.md) | None |

## What to do

1. From week 4, check the upper nodes every 2–3 days with a loupe.
2. Look where the [leaf stalk](https://genetixbay.com/knowledge/glossary/petiole.md) meets the stem, behind the stipule.
3. Wait for hairs before calling a female; a ball on a stalk with no hairs is male.
4. Label every plant and keep the record in your journal.
5. Not making seed? Remove males before the sacs open, which often happens within 1–3 weeks of flowering.

## Common mistakes

- Mistaking stipules for preflowers.
- Calling sex too early from one ambiguous node.
- Flipping the whole room just to sex plants, when a cutting would do.
- Keeping a male "to see" in the same room as females.

## Related

- Full article: [Male, female and hermaphrodite cannabis](https://genetixbay.com/knowledge/basics/sex-male-female-hermaphrodite.md)
- Guide: [Telling sex and spotting herms](https://genetixbay.com/knowledge/guides/telling-sex-and-spotting-herms.md)
- Answers: [what to do with a male plant](https://genetixbay.com/knowledge/answers/what-to-do-with-a-male-plant.md) · [when autos start flowering](https://genetixbay.com/knowledge/answers/when-do-autoflowers-start-flowering.md)
- Terms: [pre-flower](https://genetixbay.com/knowledge/glossary/pre-flower.md) · [node](https://genetixbay.com/knowledge/glossary/node.md) · [stigma](https://genetixbay.com/knowledge/glossary/stigma.md)

## Follow-up questions

**What does a female preflower look like?** A female cannabis preflower is a small teardrop-shaped bract at a node, with two white or coloured stigmas, the 'hairs', poking out of its tip. A male preflower is a small round ball on a short stalk with no hairs, which later opens into pollen sacs. Use a 30–60x loupe, and don't mistake stipules, the small leafy spurs at each node, for preflowers.

**Do I need to flip to 12/12 to see sex?** No, you don't need to flip to 12/12 to see a cannabis plant's sex. Preflowers form with age, not with the light schedule, so they appear under 18/6 or 24/0 too, usually about 4–6 weeks from seed. Flipping a cutting rather than the whole plant gives a clear answer in about 1–2 weeks without stopping the mother's veg.

**Can a DNA test tell sex from a seedling?** Yes, a PCR or PACE DNA test can identify a male cannabis plant from the first true leaves, using validated Y-linked markers, with high accuracy. It tells you the plant is genetically male or female. It cannot tell you whether a genetic female will later turn hermaphrodite; only growing her out shows that.

## Sources

1. Spitzer-Rimon B, Shafran-Tomer H, Gottlieb GH, et al. 2022. Non-photoperiodic transition of female cannabis seedlings from juvenile to adult reproductive stage. Plant Reproduction 35(4):265-277. https://doi.org/10.1007/s00497-022-00449-0
2. Spitzer-Rimon B, Duchin S, Bernstein N, Kamenetsky R. 2019. Architecture and florogenesis in female Cannabis sativa plants. Frontiers in Plant Science 10:350. https://doi.org/10.3389/fpls.2019.00350
3. Toth JA, Stack GM, Cala AR, et al. 2020. Development and validation of genetic markers for sex and cannabinoid chemotype in Cannabis sativa L. GCB Bioenergy 12(3):213-222. https://doi.org/10.1111/gcbb.12667
4. 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