14/10 light cycle explained

Why 14/10 can work

Flowering is driven by the dark period, but yield is driven by total daily light (DLI). A slightly longer day can increase DLI without changing your hardware.

• More on-hours = more photons over the day.
• More photons (within tolerance) = more growth and potentially more weight.
• The dark period still exists (10 hours), which helps keep most photoperiod plants in flower.

The DLI math in plain English

DLI (Daily Light Integral) is the total “useful light” a plant receives across a 24‑hour day. In practice it’s intensity × time. If intensity stays the same, adding hours increases DLI.

• If heat or stress rises, lower intensity when you add hours so total daily light stays similar.
• If everything stays stable, you can let DLI rise and see whether your cultivar converts it into mass.

What research suggests (and what it doesn’t)

Indoor growers default to 12/12 because it’s reliable. But controlled studies show some indoor cannabis cultivars can still flower strongly under longer-than-12‑hour days, and yield can increase — largely because longer days inherently increase DLI.

• Some cultivars produced more floral biomass at 13 hours than at 12 hours in controlled indoor trials.
• Longer photoperiods can also delay floral initiation in some genetics and setups, which can reduce output over time.
• Bottom line: this is cultivar‑dependent. Test it like an engineer: one change, one run, take notes.

Tradeoffs you can’t ignore

• Energy + heat: more light‑hours usually means more watts and more heat to remove (unless you reduce intensity).
• Flower timing: if the plant takes longer to fully set and finish, your yearly output can drop even if a single harvest is heavier.
• Night integrity: your “10 hours dark” must be real dark. Light leaks and night interruptions can delay or disrupt flowering.

When 14/10 makes sense

• You’re already harvesting consistently and want a controlled lever to test more output.
• Your canopy intensity is dialed in and your environment doesn’t swing.
• You’re running a perpetual flower workflow where small gains add up.

How to switch to 14/10 without causing chaos

1. Get a clear flower commitment first (don’t do this on day 1 of flip for strain‑sensitive plants).
2. Add time gradually: +15 to +30 minutes per day until you reach 14 hours.
3. Keep intensity stable while you change duration. Don’t change two variables at once.
4. Watch for stress: stalled growth, odd leaf posture, delayed pistils — if it happens, pause the ramp.
5. Log what you did. If you can’t repeat it, it’s not a method.

Who should avoid 14/10 (or use it carefully)

• New growers who can’t keep environment stable yet.
• Grow spaces with light leaks or any “night interruption” (your dark period must be clean).
• Strain‑sensitive genetics that react to small schedule changes.
• Plants already stressed from heat, low humidity, or wrong feeding.
• Anyone chasing “more light” instead of fixing fundamentals.

If your room swings, extra light just amplifies problems.

FAQ

Sources

• Ahrens et al. (2023) — Is Twelve Hours Really the Optimum Photoperiod for Indoor-Grown Cannabis?
• Ahrens et al. (2024) — Longer Photoperiod Substantially Increases Indoor-Grown Cannabis’ Yield and Quality (12 h vs 13 h)
• Grover et al. (2025) — Examining the “Night Break” (night interruption) method in Cannabis sativa
• Kusuma et al. (2021) — Nighttime photons can delay flowering in Cannabis sativa
• Iowa State Extension — Daily Light Integral (DLI) / PPFD basics
• Purdue Extension (HO-238-W) — Measuring Daily Light Integral in a Greenhouse (PDF)

Next steps