What are the best LED settings for a cannabis grow tent?
Target a daily light integral (DLI) of 20 to 30 mol/m²/day in veg and 35 to 45 mol/m²/day in flower. In practice that means running the fixture at 40 to 60 percent power in veg and 80 to 100 percent in flower, hung 18 to 24 inches above the canopy.
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Photoperiod stays 18/6 in veg and 12/12 in flower no matter which LED you buy. Dimmer percentage and hanging height are the two dials you adjust; PPFD is the number you measure to confirm the result.
cannabis grow tent led settings
What PPFD should a grow tent LED produce?
Vegetative plants grow well at 400 to 600 µmol/m²/s and flowering plants at 600 to 1,000 µmol/m²/s at canopy level. Seedlings and clones want 200 to 400 µmol/m²/s, so start low and raise the fixture or dim it.
cannabis grow tent led settings
Measure PPFD at the top of the canopy, not at the tent wall. A quantum sensor or a calibrated phone app gives you a rough map of hotspots, edges, and shaded lower branches.
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How do you convert PPFD into DLI?
DLI = PPFD × light hours × 3,600 ÷ 1,000,000. A 12-hour flower cycle at 900 µmol/m²/s lands near 39 mol/m²/day, which sits in the sweet spot.
Dimmer and height settings by stage
- Seedling or clone: 25 to 40 percent power, 24 to 30 inches above the canopy, 18/6 or 24/0.
- Vegetative: 40 to 60 percent power, 18 to 24 inches, 18/6.
- Early flower: 70 to 80 percent power, 16 to 20 inches, 12/12.
- Peak flower: 90 to 100 percent power, 12 to 18 inches, 12/12.
What about spectrum and scheduling?
Most current LEDs blend 3000K to 5000K white diodes with 660 nm red, and full-spectrum output works for both stages. Far-red at lights-off is optional, and the yield gain is small next to fixing DLI first.
Why does convenience decide these settings now?
App dimming, sunrise and sunset ramps, and built-in PPFD presets let growers pick a stage once and let the controller repeat it. Light management becomes a dropdown choice instead of a nightly measurement.
The trade-off is trusting a preset. Spot-check PPFD with a meter once per stage, particularly after you change tent height, plant count, or canopy shape.
Which mistakes ruin LED settings?
- Running 100 percent power in veg, which causes bleaching and heat stress.
- Ignoring DLI and chasing a single PPFD number.
- Lowering the fixture without dimming it when plants stretch.