VPD, or Vapor Pressure Deficit, is a measurement that describes the difference between how much moisture is in the air and how much moisture the air can hold at a given temperature.
WHAT IS VPD?
VPD helps explain how easily a plant can transpire, or release water vapor through its leaves. It is influenced by temperature and relative humidity and is used to dial in optimal growing conditions.
Instead of looking at temperature or humidity alone, VPD looks at how they work together.
HOW IT’S USED
Growers use VPD to:
- Set temperature and humidity targets
- Improve nutrient uptake
- Reduce plant stress
- Prevent issues like mold or slowed growth
VPD targets often change depending on the plant’s growth stage.
WHY IT MATTERS
Proper VPD helps:
- Maximize transpiration
- Improve photosynthesis efficiency
- Support healthy growth in veg and flower
- Reduce the risk of environmental problems
When VPD is off, plants may struggle even if other conditions seem correct.
LIMITATIONS & NOTES
VPD is a guideline, not a strict rule. Chasing perfect numbers without considering airflow, watering practices, or plant health can cause unnecessary adjustments. It works best as a reference tool rather than an absolute target.
Resources
- VIDEO: Mastering VPD & Dew Point: Prevent Mold and Boost Cannabis Yields (The Slow Lane)
- PODCAST: VPD – Voluminous Piss Drinking (Cultivation Conversation)