The Four Levers Are One System
How light, VPD, leaf temp, and CO2 interlock into a single throttle — the master setpoint table and the sequence to raise them without breaking the plant.
7 min read
You cannot push one master lever hard without moving the others. Turn light up and radiant load rises, so leaf temperature and VPD climb, so transpiration and CO2 demand rise. That interdependence is not a nuisance — it is the operating logic of a commercial room. Nutrient uptake rides on top of all of it, carried by the transpiration stream. This lesson consolidates the four levers into one table and one sequence.
| Stage | PPFD / DLI | VPD (kPa) | Day / Night temp | CO2 (ppm) |
|---|---|---|---|---|
| Clone / propagation | 150–250 / 10–15 | 0.4–0.8 | 75–80 °F / 72–75 °F | 400–800 |
| Vegetative | 350–650 / 20–35 | 0.8–1.1 | 72–82 °F / 65–72 °F | 800–1,200 |
| Early flower / stretch | 700–900 / 30–40 | 0.9–1.2 | 75–80 °F / 68–72 °F | 1,000–1,200 |
| Mid flower / bulking | 800–1,000 (up to 1,200–1,500 w/ CO2) / 35–65 | 1.0–1.3 | 72–78 °F / 64–68 °F | 1,000–1,200 |
| Late flower / ripen | 700–900 / 30–40 | 1.2–1.6 | 65–75 °F / 60–65 °F | 600–1,000 (taper) |
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