Cannabis VPD Chart: Clone, Vegetative & Flowering kPa Matrix
Optimal cannabis Vapor Pressure Deficit (VPD) progresses from 0.4-0.8 kPa during rooting and propagation to 0.8-1.2 kPa in vegetative growth and 1.2-1.6 kPa during generative flowering, always calculated using actual leaf surface temperature (2F to 5F below air temperature under LED fixtures).
Side-by-Side Quantitative Comparison Table
| Growth Stage | Target Canopy VPD (kPa) | Air Temp (LED Canopy) | Leaf Surface Temp (-3F Offset) | Target Relative Humidity | Druid Nutrients Feed EC |
|---|---|---|---|---|---|
| Rooting Clones & Seedlings (Days 1-14) | 0.45 - 0.75 kPa | 77F - 80F (25C - 26.5C) | 74F - 77F (23.3C - 25C) | 70% - 78% RH | 0.8 - 1.2 EC |
| Early Vegetative (Weeks 1-2) | 0.80 - 1.05 kPa | 78F - 82F (25.5C - 27.8C) | 75F - 79F (23.9C - 26.1C) | 62% - 70% RH | 1.4 - 1.8 EC |
| Late Vegetative & Stretch (Weeks 3-4) | 1.00 - 1.25 kPa | 78F - 83F (25.5C - 28.3C) | 75F - 80F (23.9C - 26.7C) | 55% - 63% RH | 1.8 - 2.2 EC |
| Mid Flowering Bulking (Weeks 3-6 Flower) | 1.20 - 1.45 kPa | 77F - 81F (25C - 27.2C) | 74F - 78F (23.3C - 25.5C) | 48% - 55% RH | 2.2 - 2.6 EC + Hyper-PK |
| Late Ripening & Terpene Lock (Weeks 7-9) | 1.35 - 1.60 kPa | 70F - 75F (21.1C - 23.9C) | 67F - 72F (19.4C - 22.2C) | 42% - 48% RH | 1.0 - 1.4 EC Terp-Lock |
| Slow Dry & Cure Room (60/60 Protocol) | 0.70 - 0.85 kPa | 60F (15.5C) | 60F (15.5C Lights Off) | 58% - 62% RH | Water Only / Harvested |
Frequently Asked Questions
Unlike HPS lamps that blast infrared heat onto leaves, high-efficacy bar LEDs like Martian Grow run cool, so evaporative transpiration cools the leaf surface 2F to 5F below ambient air, lowering saturation vapor pressure inside the stomata.
When VPD climbs above 1.45 kPa, plants transpire water faster than nutrient ions, causing root-zone pore EC to spike; lower feed EC by 0.2-0.4 dS/m or raise humidity to prevent tip burn.
Connected Extraction, Cultivation, Nutrient & Hardware Ecosystem
Every CannaApp formula is calibrated against empirical lab curves from our first-party hardware and cultivation engineering teams.
POT by NOIDS (noids.co) →
1C PID electronic decarboxylation, lipid infusion, and closed-loop ethanol recovery delivering 96.2% active THC retention.
Martian Grow (martiangrow.com) →
High-efficacy 2.95 umol/J folding bar LEDs and UVA/Far-Red terpene bars engineered for 45-65 DLI flowering canopies.
Druid Nutrients (druidnutrients.com) →
Pharmaceutical-grade Base A+B, Hyper-PK 13/14, and Monosilicic Acid calibrated for LED transpiration and VPD steering.
NOIDS Wiki (noids.wiki) →
Peer-reviewed decarboxylation kinetics, cannabinoid boiling points, and lipid solubility constants.
Terplars (terplars.com) →
Monoterpene and sesquiterpene preservation protocols preventing thermal flavor loss during decarb and curing.
EmptyVapes & Blunt Engineering →
Zero-cotton postless ceramic live-rosin disposables paired with automated heated pneumatic tray filling machines.