# Autoflower

> A day-neutral cannabis plant that starts flowering by age, usually a few weeks after germination, regardless of light schedule; the trait is mainly recessive.

- Canonical: https://genetixbay.com/knowledge/glossary/autoflower.html
- Also written: autoflowering, auto, autos, day-neutral, day neutral, autoflowering cannabis, autoflowering seeds
- Glossary category: Plant biology · 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"

An autoflower is a day-neutral cannabis plant: it switches to flowering at a set developmental age, typically 3-5 weeks from [germination](https://genetixbay.com/knowledge/glossary/germination.md), rather than in response to long nights. Seed to harvest is often about 9-12 weeks. The trait comes from northern, short-season populations (often labelled [ruderalis](https://genetixbay.com/knowledge/glossary/ruderalis.md)) and is controlled mainly by a [recessive](https://genetixbay.com/knowledge/glossary/recessive.md) locus mapped as *Autoflower1* (Toth et al. 2022), so both parents must carry it for true-breeding autos.

## In practice

Autos can run under [18/6](https://genetixbay.com/knowledge/glossary/18-6.md) or 20/4 from seed to harvest, and growers stagger them for [continuous harvests](https://genetixbay.com/knowledge/glossary/perpetual-harvest.md).

House positions:
- **Any setback costs time**: an auto runs on a fixed countdown from germination and can't recover lost days.
- **Transplanting is almost a no-no**: plant in the final container (founder observation on taproot reaction).
- **Train, don't top**: topping never matches proper LST on an auto.
- **"Good for beginners"** is true only because autos quickly show who has a green thumb, not because they forgive mistakes.

Yield per square metre per year is very hard to beat with autos. [Cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) levels usually sit slightly under [photoperiod](https://genetixbay.com/knowledge/glossary/photoperiod.md) sisters, though elite autos can match them.

## Don't confuse with

- **Photoperiod**: flowers in response to long nights.
- **Fast version**: a photoperiod hybrid bred for short flowering, not day-neutral.
- **Ruderalis**: the source populations, not a synonym for every auto.

## Related terms

[Photoperiod](https://genetixbay.com/knowledge/glossary/photoperiod.md), [Ruderalis](https://genetixbay.com/knowledge/glossary/ruderalis.md), [Taproot](https://genetixbay.com/knowledge/glossary/taproot.md), [Short-day plant](https://genetixbay.com/knowledge/glossary/short-day-plant.md)

## Read more

- [Photoperiod vs autoflower, and how autoflowering is inherited](https://genetixbay.com/knowledge/basics/photoperiod-vs-autoflower.md)
- [Breeding autoflowers: getting the trait into a photoperiod line](https://genetixbay.com/knowledge/breeding/breeding-autoflowers.md)

## Sources

1. Toth JA, Stack GM, Carlson CH, Smart LB. 2022. Identification and mapping of major-effect flowering time loci Autoflower1 and Early1 in Cannabis sativa L. Frontiers in Plant Science 13:991680. https://doi.org/10.3389/fpls.2022.991680
2. Kurtz LE, Brand MH, Lubell-Brand JD. 2023. Gene dosage at the autoflowering locus effects flowering timing and plant height in triploid cannabis. Journal of the American Society for Horticultural Science 148(2):83-88. https://doi.org/10.21273/JASHS05293-23