Photoperiod Guide
How Long Should Grow Lights Be On for Indoor Plants?
The right lighting time depends on crop type, growth stage, fixture output and target DLI. Agrilumia helps growers build practical LED grow light schedules for stable production.
Quick Answer
Most indoor crops need 12 to 18 hours of light per day.
Leafy greens and young plants often perform well with 14 to 18 hours of light. Flowering crops may require shorter or crop-specific schedules. The correct answer is not only the number of hours; it is the balance between light intensity and total daily light.
Commercial growers should use PPFD and DLI together. A stronger fixture can run for fewer hours, while a lower-output fixture may need a longer schedule to reach the same daily light target.
Lighting Schedule
Recommended starting points by plant stage
These ranges are starting references. Always adjust according to crop response, temperature, humidity, CO2 and cultivation density.
| Plant Stage | Daily Light Time | Grower Notes |
|---|---|---|
| Seedlings and clones | 14-18 hours | Use moderate intensity to avoid stress while encouraging compact, healthy growth. |
| Vegetative growth | 16-18 hours | Higher light can increase biomass when nutrition and environment are controlled. |
| Leafy greens and herbs | 14-18 hours | Manage DLI carefully to improve yield, color, flavor and uniformity. |
| Flowering and fruiting crops | 12-16 hours | Some crops are photoperiod sensitive, so crop-specific scheduling is important. |
Why DLI matters more than a fixed number of hours
DLI, or Daily Light Integral, describes the total amount of photosynthetically active light delivered to plants in one day. Two rooms can both run lights for 16 hours, but the crop result can be completely different if one room has twice the PPFD.
For B2B projects, Agrilumia recommends planning lighting with the crop target first, then selecting fixture wattage, mounting height, spacing and dimming strategy. This approach reduces wasted electricity and helps the grower avoid both under-lighting and light stress.
Should grow lights run 24 hours a day?
In most professional cultivation, no. Plants need a dark period for normal biological processes. A 24-hour schedule can increase electricity cost and may create stress, especially when intensity is already high. There are exceptions in research or special propagation methods, but they should be tested carefully.
How Agrilumia helps with lighting schedules
Agrilumia LED grow lights support dimming, daisy chain control and series options from quantum boards to high-power foldable fixtures. For commercial projects, we can help estimate fixture quantity, layout, mounting height and operating schedule according to your cultivation area and crop goal.
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