Perfect Grow Room Environment – VPD Chart

The chart below shows VPD levels that are widely accepted and recommended for growing cannabis. The top of this chart is the RH or Relative Humidity in your grow room. The left displays temperature in both F and C of the air in and around the canopy of the plants. VPD (Vapor Pressure Deficit) is a control value for evaporation and plant transpiration.


VPD Chart for CannabisDownload VPD Chart


Generate a VPD chart for your room based on growth stage and leaf temperature

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The above values are measured in KpA or kilopascals. The higher the value in the chart, the higher the VPD is. The lower the value, the lower the VPD. Ideally, you want your numbers to be in the green zone for optimal vegetative and flowering growth.

The higher the VPD, the faster the plants will transpire, and the quicker your root zones will dry out. In high VPD situations, nutrients will accumulate faster and plants will favor water over food. If you’re stuck in a high VPD situation and can’t fix it, it’s always better to feed on the lighter side of things to avoid over-feeding your plants.

SensorPush HT1 Wireless Thermometer/Hygrometer for iPhone/Android. USA Developed and Supported Humidity/Temperature/Dewpoint/VPD Monitor/Logger. Indoor/Outdoor Smart Sensor with Alerts
  • Accurate: Swiss-made sensing component with accuracy of ±3%RH, ±0.3°C / 0.5°F. Professional-grade components, assembled into devices you can trust. For even more demanding applications, the device is easily calibratable to a trusted reference, or try the SensorPush HT.w or HTP.xw for even greater out-of-the-box accuracy. Whichever SensorPush you choose, you'll enjoy reliable, quality monitoring of environmental conditions including air temperature, relative humidity, dewpoint and VPD
  • Versatile: With its small, attractive design, the HT1 is at home just about anywhere: in a refrigerator, freezer, greenhouse, humidor, wine cellar, instrument case like guitar or violin, a piano, outside as a mini weather station, around the house monitoring a humidifier or thermostat in baby nursery, in the attic, basement, crawlspace, reptile tank, terrarium, plants in a grow tent, drying and curing, a chicken coop or egg incubator and more
  • Flexible: Use the sensor and your phone via Bluetooth or add a SensorPush G1 WiFi Gateway (sold separately) for data and alerts via Internet. With a G1 Gateway, get updates and push notifications when conditions exceed min/max alarm settings anywhere, ask Alexa for updates, or view data on a computer in our web dashboard. Great for a vacation home, garage, server room, data center, ensuring a dog or other pets are safe in an RV (cellular hotspot required) or anywhere remote monitoring is useful
  • Powerful: Line of sight Bluetooth range of 325 feet keeps you up to date, even on the other side of your home. Obstructions such as walls or doors will reduce this, often considerably, but every day in real world conditions, customers happily monitor difficult situations like walk-in coolers, safes, inside a wall or even on a roof. The small size, convenient mounting hole, and long battery life (typically over 2 years) simplify placing one or multiple sensors wherever they are needed most
  • Easy one-time setup with our beautifully designed, free app (iOS or Android). Quickly view a digital summary of current conditions for your entire system of connected SensorPush devices. Drill deeper with integrated data logging and graphing with 20 days of storage on the sensor and unlimited in-app storage for unlimited devices using our custom built high performance database. Export any data recording to CSV for analysis or archival with Excel, Google Sheets, etc, and calibrate with ease.

If VPD is too low, plants will start showing Calcium deficiencies and more Calcium will not fix the problem. In low VPD environments plants struggle to move Calcium through their tissue and spots will begin to occur on the leaves, starting at the top and moving down. Low VPD environments are also notorious for breeding fungal diseases like powdery mildew.

The ideal VPD for cannabis clones is around 0.8kPa
The ideal VPD for cannabis in the vegetative stage is around 1kPa
The ideal VPD for cannabis in the flowering stage is 1.2 – 1.5kPa

*Important Note: Prevent relative humidity from going over 80% or below 50%. If you are unable to hit your desired targets, use the chart to find a combination that gets you as close to the green area as possible. Most growers understand that during the veg stage of growth a higher humidity is acceptable and if you are able to control your environment with both a humidifier and dehumidifier, we suggest you shoot for a higher VPD during the vegetative growth stage.

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