# 24/0

> 24/0 means lights on 24 hours a day with no dark period; GenetixBay endorses it for veg, as cannabis does not need a sleep period before flowering.

- Canonical: https://genetixbay.com/knowledge/glossary/24-0.html
- Also written: 24-0, 24/0 light cycle, 24 hours light, lights on 24/7, continuous light
- Glossary category: Environment and light · Evidence: Grower practice
- 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"

24/0 is a schedule with continuous light and no dark period. [Photoperiod](https://genetixbay.com/knowledge/glossary/photoperiod.md) cannabis stays vegetative under it, because long uninterrupted darkness is what triggers flowering. It is used in veg and for clones, and by some growers for [autoflowers](https://genetixbay.com/knowledge/glossary/autoflower.md).

## In practice

24/0 gives the highest [DLI](https://genetixbay.com/knowledge/glossary/dli.md) for a given [PPFD](https://genetixbay.com/knowledge/glossary/ppfd.md): 400 µmol/m²/s on 24/0 delivers about 35 mol/m²/day, the same as 540 µmol/m²/s on [18/6](https://genetixbay.com/knowledge/glossary/18-6.md). That lets growers run a fixture dimmer, closer and more evenly for the same daily light, which can suit [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) and clones.

Costs: higher electricity use and no cool night to drop room temperature or humidity. Watch for interveinal leaf mottling or [chlorosis](https://genetixbay.com/knowledge/glossary/chlorosis.md) in some cultivars under continuous light, a response documented in several other crops. If a cultivar shows it, switch to 20/4 or 18/6.

## Don't confuse with

- **18/6**: the conventional veg schedule.
- **24/0 in flower**: photoperiod plants will not flower under it; autoflowers will, but results vary.

## Myth check

GenetixBay house position: **24/0 in veg is endorsed.** Cannabis does not need a "sleep period" in veg. The claim that plants must have darkness every day to grow well is a *Myth* for vegetative cannabis. Grower experience is broad (*Grower practice*); controlled cannabis data are limited, and members are welcome to run a [Mythbusters](https://genetixbay.com/knowledge/mythbusters.md) trial of 24/0 vs 18/6 on their own cultivars.

## Related terms

[18/6](https://genetixbay.com/knowledge/glossary/18-6.md), [12/12](https://genetixbay.com/knowledge/glossary/12-12.md), [Photoperiod](https://genetixbay.com/knowledge/glossary/photoperiod.md), [DLI](https://genetixbay.com/knowledge/glossary/dli.md)

## Read more

- [Photoperiod and light leaks: 18/6, 12/12 and the dark period](https://genetixbay.com/knowledge/environment/photoperiod-light-leaks.md)

## Sources

1. Zhang M, Anderson SL, Brym ZT, Pearson BJ, 2021. Photoperiodic flowering response of essential oil, grain, and fiber hemp (Cannabis sativa L.) cultivars. Frontiers in Plant Science 12:694153. https://doi.org/10.3389/fpls.2021.694153