🌟 Happy New Year! 🌟

Advanced Nutrients Logo

🌟 Happy New Year! 🌟

🌟 Happy New Year! 🌟

Using a VPD Cannabis Chart to Optimize Plant Performance

Subscribe now and enjoy more helpful content like this for free!

Why should indoor cannabis growers understand vapor pressure deficit?

Because vapor pressure deficit (VPD) affects whether your plants can breathe, grow, and thrive!

You see, vapor pressure deficit readings tell you how much moisture is currently in your grow room’s air versus the maximum amount of moisture that air can hold. And this difference directly affects the transpiration rate of your plants: i.e., how much water they’re releasing into the air.

If your grow room VPD is off, your cannabis plants experience massive stress that severely lowers the size and quality of your harvest.

Why VPD Matters

Your cannabis plants breathe through mouth-like openings in the bottom of their leaves called stomata.

Cannabis plant leaves open and closed stomata graphic

These stomata inhale carbon dioxide (C02). They exhale oxygen and moisture.

With an optimal VPD, your plants will open their stomata and transpire faster, fueling photosynthesis for vigorous growth. By transpiring at the optimal rate, your plants will also be able to increase nutrient uptake. And of course, open stomata means a greater amount of CO2 can be absorbed, leading to better overall development.

As you can see, achieving the right VPD is critical to maximizing plant performance.

What Happens When Your VPD Is Too Low or Too High?

A high vapor pressure deficit means your grow room air has the capacity to hold much more water than what’s already present…

And your cannabis plants will transpire more water out of their tissues into the air.

A low vapor pressure deficit means that your grow room air is at or near moisture saturation…

And your plants will be much less able to transpire water out of their tissues into the air.

Too high or too low vapor pressure deficits cause major problems, such as…

  • Your plants shut down C02 intake, slowing down or stopping photosynthesis altogether.
  • Your plants take in too much water, causing potential nutrient burn.
  • Your plants transpire less, negatively affecting their metabolism, water, and nutrient intake.
  • Your leaves become susceptible to molds, fungi, pests, and other problems.
  • Clones and seedlings struggle or die.
  • Buds get moldy.
  • Powdery mildew spreads like wildfire.


As you can see, improper vapor pressure deficit can lead to plant harm and even grow room disasters.

Cannabis greenhouse growing

And even worse, growers who don’t know about vapor pressure deficit might misdiagnose the problem.

For example, they might think their plants are wilting or overwatered…

Overfed or underfed…

Or sick from a disease that’s sapping them of their growth rate and energy.

Well, here’s the good news. You CAN control VPD — and when you do, you’ll see much better performance from your cannabis plants…

Because you’ll spare them plant stress that can cost you harvest weight and potency.

Pinpointing Your Optimal Vapor Pressure Deficit Zone With a VPD Chart

Below is a VPD chart for cannabis showing you the ideal vapor pressure deficit zone for various temperatures in your grow room. The temperature indicates the maximum amount of water your grow room’s air can hold, while the relative humidity indicates how much water vapor is currently present in the atmosphere.

Take a look below.

Cannabis VPD chart for ideal grow room temperature and humidity

The “green zone” is where you want your cannabis grow room relative humidity to be.

For example…

Imagine it’s 77°F at canopy level and you’re in the late grow phase.

According to this VPD chart, you’ll want a range of 65-80% relative humidity to maintain the optimal vapor pressure deficit.

And if you’re growing fat Indica buds, you’d choose 65% relative humidity for your grow room, to minimize the risk of botrytis and other pathogens.

Or say you’re running C02 and your leaves at canopy level are 84°F.

You want your relative humidity to be 70-85%, approaching the lower level if you have fat, dense buds on your plants.

How To Adjust Relative Humidity In Your Grow Room

Lowering relative humidity is easy—you use a dehumidifier.

However, in many cannabis grow rooms (especially in the western United States), relative humidity is too low, creating an unfavorably high VPD.

Simply put, a high VPD means the pressure inside your cannabis plants is much higher than in the outside air.

Because of this, your plants will transpire an abundant amount of moisture into the air, which can…

  • Dry out their stomata.
  • Cause them to uptake so much water that they overdose on nutrients.
  • Trigger stress responses that use up your plants’ energy and metabolism trying to deal with high VPD rather than focusing on growth and bud production.


Cannabis grow room himidifier

To add moisture into the air, cannabis growers use grow room humidifiers.

And keep in mind, the VPD chart also enables you to…

Measure Your Cannabis Leaf Temperatures

Remember, the temperature will tell you how much water your grow room air can hold.

Instead of relying on a general thermometer reading for the entire room, use a handheld digital thermometer to measure the temperature at the bottom of your leaves. See this article for more information & tips on the optimal cannabis leaf temperature.

You can also consider using a vapor pressure deficit meter rather than relying on a grow room temp and humidity chart.

As with most cannabis grow room strategies and conditions, it’s crucial to monitor and adjust your use of vapor pressure deficit in order to achieve optimal results.

Take into account whether your grow room or strains are susceptible to pests, gray mold, powdery mildew or other problems affected by relative humidity… And do your best to control relative humidity to optimize vapor pressure deficit, without creating conditions that assist gray mold, powdery mildew, etc.

Bottom line…

It may take time to get it right, but once you master your vapor pressure deficit, your plants will reward you with optimal performance and a much more satisfying harvest.

Did you like this article? Sign up for the Advanced Nutrients newsletter and get notified when we publish new growing tips and resources from our cannabis experts.

Subscribe now and enjoy more helpful content like this for free!


Latest Posts

About the Author

The Advanced Nutrients Team

Since 1999, Advanced Nutrients has been committed to educating the community and bringing the most up-to-date knowledge to the forefront of grows across the globe. Every article you read here has been curated by Advanced Nutrients’ industry experts, so you can continue raising your bud weight… and your reputation.

Advanced Nutrients Leaf Logo

Get More Articles Chock-Full of Cultivation Tips, Tricks, and Strategies Delivered Straight To Your Inbox

Sign up for our free newsletter and receive more relevant cannabis cultivation content right in your inbox! Subscribe below.

Chat with Buddy AI

buddy image
buddy image
minimize chat

minimize chat window

Hi, I'm Buddy, and I am powered by OpenAI' ChatGPT. Ask me a question. Here are some example topics: Example 1: What is the best way to germinate my seeds? Can you explain in much detail as possible. Example 2 : What Advanced Nutrients' base nutrient should I use for growing cannabis at home? As AI is prone to errors, the information provided should be used as a general guide, not as a definitive source. If you are experiencing problems and trying to troubleshoot, contact our experts here for free.


Discover the secrets of the top 1% growers worldwide!

Growers get ready to maximize yields and potency while minimizing costs.

send message
Need Help Growing?

Over time, components within the nutrients settle on the bottom of the bottle. When you pour a bottle without shaking it, you can potentially be pouring out an unbalanced solution. Shaking up the nutrient bottle ensures you are pouring the right blend into your reservoir, giving your crops the nutrition they need.

Usually, it’s not a problem. But some products are incompatible with each other and can damage your plants when they’re used together. For example, bloom boosters with high PK numbers or low-grade silica products can destabilize your nutrient mix and cause nutrient lockout.

Nutrient manufacturers design their products to be used with each other. In doing so, they include specific portions of each nutrient in each product, so crops receive the right nutrition through each stage of the grow cycle. When you stick with one manufacturer, you don’t have to worry about inadvertently destabilizing your nutrient mixture. One example of why you need to stick with only one manufacturer’s products is Advanced Nutrients’ pH Perfect line. These products are designed to keep your crops’ root zone within a specific pH range. When you use them alongside products from another manufacturer, we can’t guarantee your root zone will maintain its optimal pH level.

Yes! If you’re growing with Advanced Nutrients products, you can use our easy nutrient calculator to generate the correct nutrient chart for your crops in seconds. Check out Advanced Nutrients’ nutrient calculator here. Another great resource is our library of free custom-growing recipes. Try our expert grower-tested nutrient schedules here.

You can also download our official BudLabs app to generate nutrient schedules and receive real-time notifications for specific tasks, including feeding your crops. Upgrade to BudLabs Pro to maintain profiles on an unlimited number of crops.

If you are a grower, visit this link to find the closest Advanced Nutrients Authorized Retailer. If you are a retailer, visit this link to identify our official distributors.

Our greatest passion is growing great cannabis—and helping other growers do the same. That’s why we offer complimentary cultivation support 24/7 from Monday to Friday and from 9 AM until 7 PM PST on Saturday… With the same level of advice licensed producers would pay consultants tens of thousands of dollars to unlock.
Just call 1-800-640-9605 or email support@advancednutrients.com. For Spanish-speaking growers, email spanishsupport@advancednutrients.com.

Yes! If for any reason you are not absolutely thrilled with the results you achieve when you use our products, just bring the unused portion, along with your original sales receipt, back to the place of purchase within six months, and ask for your money back. Find out more about our Grower Guarantee here.

Advanced Nutrients has spent many thousands of man-hours developing a technology that automatically balances your pH for you — putting it in the “sweet spot” and holding it there for one week.

And the technology is so “smart” that it can account for many of the aforementioned variables in your grow room. Our proprietary pH buffering agents and stabilizing mechanisms became the foundation of a new system aptly called pH Perfect® Technology. Learn all about it here.

Change Region

If your country/region is not listed on this page, please find your local Contact Details, Authorized Retailer and Grower Support on our Global Site.

United States