Environment · 1 PAGE
HPS environmental guide
Lighting, VPD, leaf temperature and CO₂ targets under HPS.
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Weekly light (PPFD and DLI), leaf VPD, leaf temperature, night temperature and CO₂ targets for growing under HPS lighting.
| Stage / week | Starts | PPFD | DLI | Leaf VPD (kPa) | Leaf (°f) | Night (°f) | CO2 (ppm) |
|---|---|---|---|---|---|---|---|
| Clone | – | 60 | 5.18 | 0.5 | – | – | – |
| Veg 1 | Day 1 | 200 | 12.9 | 0.7 | 81 | 81 | 450 |
| Veg 2 | Day 8 | 375 | 24.3 | 0.8 | 82 | 82 | 550 |
| Veg 3 | Day 15 | 500 | 32.4 | 0.9 | 83 | 82 | 650 |
| Veg 4 | Day 22 | 500 | 32.4 | 0.9 | 83 | 82 | 700 |
| Flower 1 | Day 1 | 800 | 34.5 | 0.9 | 83 | 77 | 1000 |
| Flower 2 | Day 8 | 850 | 36.7 | 0.9 | 83 | 77 | 1050 |
| Flower 3 | Day 15 | 900 | 38.8 | 1.0 | 82 | 77 | 1100 |
| Flower 4 | Day 22 | 1000 | 43.2 | 1.1 | 82 | 72 | 1200 |
| Flower 5 | Day 29 | 1000 | 43.2 | 1.1 | 82 | 72 | 1200 |
| Flower 6 | Day 36 | 1000 | 43.2 | 1.2 | 81 | 71 | 1200 |
| Flower 7 | Day 43 | 925 | 39.9 | 1.3 | 80 | 70 | 1125 |
| Flower 8 | Day 50 | 800 | 34.5 | 1.4 | 78 | 68 | 1000 |
| Flower 9 | Day 57 | 600 | 25.9 | 1.5 | 75 | 65 | 800 |
Light hours
DLI values assume 24-hour light for clones, 18 hours in veg and 12 hours in flower. Leaf VPD uses leaf temperature, not air temperature.
CropSalt VPD calculator
Use the VPD calculator on our website to manage your environment. Supplemental CO2 is optional — follow the same light and feed chart without it.