Are you struggling with poor growth of your cannabis plant or inconsistent yields? That is what a lot of growers complain about. Grow your cannabis plants with great precision by controlling various environmental aspects. Some of the vital factors influencing plant health and growth include temperature, humidity, light intensity, and air circulation. One important factor that often gets overlooked but can make a big difference in growing healthy, high-yielding crops is Vapor Pressure Deficit (VPD). It is the key to unlocking better results for your cannabis plant.
For many cannabis growers, understanding VPD for cannabis is the secret ingredient to growing thriving plants with optimal nutrient uptake and efficient transpiration.
Whether you’re working with autoflowers, seedlings, or plants in the flowering stage, each growth phase has its own ideal VPD range, and knowing how to manage it can improve your overall crop health.
This article will examine VPD, its role in plant growth, and its calculation using VPD charts. We’ll also discuss the use of VPD for cannabis during propagation, vegetative growth, flower induction, and the entire flowering cycle. Let’s dive deeper.
What is VPD and Why Does it Matter?
VPD is a measure of the difference between the amount of moisture the air can hold at a given temperature and the actual amount of moisture in the air. It can be simply described as how dry or humid the air is. Here is why it matters:
- Controls Transpiration: VPD determines the amount of water that must be released through the leaves. This is essential for nutrient uptake, cooling the plant, and overall well-being. Incorrect VPD can jeopardize this process.
- Maintains Optimal Nutrient Uptake: A correct VPD means the uptake of nutrients happens correctly. A too-high or too-low VPD leads to deficiencies or toxicities.
- Maintains Perfect Temperature and Humidity: VPD maintains the right temperature and humidity in your growing space, avoiding the growth of mold, dehydration, and stress.
- Reduces Stress on Plants: Adequate VPD levels prevent stress from occurring by balancing water loss and intake, allowing the plant to grow stronger and healthier.
- Increases Growth and Yield: Cannabis grown under the perfect VPD range grows faster, stronger, and produces higher yields.
- Supports Plant Health: Proper VPD helps strengthen the plant’s immunity, making it more resistant to pests and diseases.
- Helps Save Resources: Maintaining the right VPD helps optimize the use of water and energy, saving on time and costs.
So, what are the factors that influence the VPD levels in cannabis?
Factors That Influence VPD in Cannabis
Several factors influence the VPD levels in cannabis plants. Some of them are:
- Temperature: The ambient air temperature impacts the ability of the air to hold moisture. Higher temperatures will increase the potential for higher VPD, whereas cooler temperatures will lower it.
- Humidity: The relative humidity in the grow space determines the VPD level. The higher the humidity, the lower the VPD, as it increases the amount of moisture in the air. Conversely, the lower the humidity, the higher the VPD, as more water is pulled out from the plant.
- Leaf Temperature: The temperature of the leaves can be different from the ambient air temperature. This temperature affects transpiration rates and, hence, the calculation of VPD, especially under grow lights.
- Light Intensity: High light intensity can elevate the leaf temperature, increase transpiration, and change the VPD in the growing environment.
- Airflow and Ventilation: Air must be distributed evenly for stable conditions and even distribution of heat and humidity. Poor ventilation in areas allows localized hot spots or areas of high moisture, disrupting VPD.
- Plant Stage: VPD varies at different plant growth stages. Vegetative plants require a higher VPD for significant growth, while flowering plants require slightly less VPD to perfect bud development.
- Time: VPD can vary depending on the time of day. During the day, with higher temperatures and light intensity, VPD is generally higher than at night, when the grow room cools down.
- Weather: Outdoor weather conditions, such as high humidity or dry air, can affect indoor VPD levels if your grow room is not sealed or has no climate control.
- CO2 Levels: Increased CO2 levels can contribute to transpiration rates, thus altering VPD. Under elevated CO2, plants often increase transpiration, influencing the desirable VPD values.
Understanding VPD and how it works can significantly improve the efficiency of your grow room, whether indoors with LED lights or outdoors. Let’s discuss what happens when there is an imbalance of VPD.
Consequences of Improper VPD Levels
When VPD is not optimal, it can create a number of issues on a cannabis plant, including:
- Poor Transpiration: Incorrect VPD creates an imbalance in regulating the loss of water, due to which the plant faces dehydration or excessive moisture levels.
- Nutrient Imbalance: Incorrect VPD balances prevent nutrient uptake, cause deficiency or toxic accumulation
- Stunted Growth: Excessive and low levels of VPD can deter plant growth, as they affect photosynthesis and cell expansion.
- Mold and Disease Risks: Low VPD (high humidity) creates conditions conducive to the development of mold, mildew, and pathogens.
- Low Bud Quality: Stress generated from improper VPD leads to poor bud quality and yield in terms of cannabinoids produced.
Now that we know about the impact and consequences of VPD on nutrient uptake in cannabis plants let us understand how to calculate and use VPD charts and tools.
Calculating and Using VPD Charts and Tools
Measuring two of the most critical environmental factors, temperature and humidity, is necessary to manage VPD for cannabis cultivation effectively. You can calculate VPD using a formula, an online calculator, or a VPD chart. Proper VPD management ensures optimal growth at every stage of your cannabis plant’s development.
How to Calculate VPD for Cannabis:
- Take Measurement of Temperature: Record how many degrees Celsius or Fahrenheit the temperature is in the grow space.
- Measure the Relative Humidity (RH): Find how much percent the relative humidity measurement is.
- Use a VPD Calculator or Chart: Plug temperature and RH values into an online VPD calculator or check a VPD chart. The VPD value, usually given in kilopascals (kPa), determines whether the growing environment falls within the optimum range.
Tools and Formulas for Calculating VPD:
- VPD Calculator and Formula
Free online VPD calculators make the task much easier. If you know the ambient temperature and RH, you can easily get the value of VPD. Many modern grow lights, climate control systems, and apps come with an inbuilt VPD calculator that eliminates guesswork and ensures the ideal conditions.
If you want to calculate manually, then use the following formula:
VPD = Saturation Vapor Pressure (SVP) − Actual Vapor Pressure (AVP)
- SVP is taken from the temperature tables.
- AVP is calculated by relative humidity and temperature values.
For a less technical approach, use this simplified formula:
VPD=(1− \100RH )×0.6108×exp( T+237.317.27×T )
Where:
T = Temperature in Celsius
RH = Relative Humidity (as a percentage)
- Measurement Devices for Temperature and Humidity
Accuracy in measuring temperature and humidity is needed to maintain the right VPD. Digital thermometers and hygrometers give direct measures of temperature and humidity. High-end models may be equipped with built-in VPD charts or can connect to smartphones to monitor and fine-tune in real-time.
By using these tools and methods, you would be able to maintain ideal VPD for all your growth stages, making cannabis healthier and more productive plants.
Now that we know how to calculate VPD, let us understand an ideal VPD range for your cannabis plant.
Ideal VPD Ranges for Different Cannabis Growth Stages
All stages of cultivation require different ranges of VPD to ensure optimal transpiration and nutrient uptake. Here is an overview of the ideal VPD for each stage:
- Seedling Stage: Sensitive seedlings require a higher VPD to avoid excessive moisture loss. The ideal VPD for seedlings is between 0.6 and 0.8 kPa, which provides the plant with the perfect amount of water loss when developing its root system.
- Vegetative Stage: In vegetative growth, plants concentrate on producing leaves, stems, and roots. The optimal VPD for vegetables is about 0.8–1.2 kPa. This VPD promotes good growth and ensures that the plant uptakes sufficient nutrients.
- Flowering Stage: The optimal VPD for the formation of buds is essential. VPD values between 1.0 and 1.5 kPa can prevent excessive moisture accumulation, which can cause mold and mildew, without compromising efficient transpiration and nutrient uptake.
Now, let’s understand how to use VPD charts properly to improve your cannabis yields.
How to Use VPD Charts Effectively
A VPD chart will guide you to the appropriate temperature and humidity levels for every growth stage of your plant. For example, a VPD chart for auto flowers will have different ranges compared to a VPD chart for cannabis plants in the vegetative or flowering stages. Keeping the VPD for cannabis within the optimal range will prevent common problems such as excessive water loss or slow nutrient uptake.
VPD Chart Utilization in Cannabis Growth Stages
As your cannabis plants go through each growth stage, the ideal VPD for cannabis will change. Here is a simplified breakdown of the optimal VPD at each stage:
- Propagation/Seedling Stage
- Seedlings should have a low VPD, about 0.6–0.8 kPa, to minimize moisture loss.
- Humidity should be 65%–80%, with temperatures at 70°F–75°F (21°C–24°C).
- High humidity allows young plants to absorb moisture as they develop roots and leaves.
- Vegetative Stage
- VPD for the vegetative phase should be between 0.8 and 1.2 kPa for excellent, healthy growth.
- 75°F–80°F (24°C–27°C) is the ideal temperature, and relative humidity should be between 50%–70%.
- This range will enhance nutrient uptake and strong plant growth.
- Flowering Phase
- VPD at flower should be between 1.0 and 1.5 kPa to support the healthy development of buds.
- Temperature should remain around 65°F–75°F (18°C–24°C), and the relative humidity should be about 40%–60%.
- The proper VPD for flowering will avoid mold and give robust growth of flowers.
Now, let us discuss some practical tips for managing VPD.
Practical Tips for Managing VPD
Proper management of VPD for your cannabis is essential. Here’s what you can do to control temperature and humidity in your growing space as per your yield:
- Adjust for light intensity: If you’re using LED lights, you’ll need to adjust your VPD chart for LED setups. These lights give off less heat than traditional lights, which can affect temperature and humidity.
- Room size: Small or large rooms can affect airflow and heat distribution differently, which can affect the VPD. Therefore, you’ll need to adjust your chart according to your particular environment.
- Monitor airflow and heat: Your cannabis VPD chart should account for varying airflow conditions, which can cause fluctuations in humidity and temperatures in your grow room.
- Monitor and adjust: Using a VPD chart for marijuana is only the beginning. Keep close tabs on the actual conditions that are happening in your growing space and make adjustments to create optimal conditions for your crops.
Are you worried about tracking the progress of your cannabis cultivation? Here is a simple way to do that: PlanaCan simplifies task scheduling by allowing you to define and automate cultivation processes using customizable templates. For specific strains or harvest cycles, you can outline each step from the first planting to the last harvest. Once your templates are ready, you can schedule tasks on a calendar with just a few clicks, ensuring a streamlined and consistent workflow.
Next, let us discuss the challenges that you might face with VPD readings.
Common Challenges with VPD Charts
Some common problems that may arise with growers when they use VPD charts include the following and their solutions:
- Incorrect Readings: Malfunctioning or inaccurate temperature and humidity sensors cause miscalculated VPD, leading to inappropriate environmental changes.
Solution: Calibrate your temperature and humidity sensors regularly for proper readings.
You can also buy quality sensors to reduce the chances of errors and for better reliability.
- Leaf Temperature: Leaf temperature may deviate from the ambient air temperature, causing variability in the transpiration rate and inaccurate VPD measurement.
Solution: Use an infrared thermometer to measure leaf temperature directly. This will ensure that disparity is considered. To make moisture regulation more precise, the VPD calculation uses different levels of ambient air temperature and that of the leaf.
- Environmental Changes: Temperature, humidity, and weather fluctuations can cause day-to-day or seasonal fluctuations in VPD, making it challenging to maintain a constant growth environment.
Solution: To avoid stress from drastic environmental changes, maintain the VPD levels by observing them regularly and gradually adjusting them. You can also use climate control systems that automatically adjust the VPD using real-time data to stabilize conditions, especially during the transition from vegetative to flowering stages.
Conclusion
Maintaining the right VPD for cannabis is crucial to ensure your plants thrive at every stage of growth. Whether you’re managing VPD for seedlings, adjusting for the vegetative stage, or optimizing VPD during flowering, understanding and controlling this factor can significantly impact your plants’ health, nutrient uptake, and overall yield.
With the help of PlanaCan, cannabis growers can easily manage their VPD charts and fine-tune their environmental conditions to create the best possible conditions for their crops. Our software offers practical tools and personalized support to help you maintain the ideal VPD throughout the growing process.
If you’re ready to take the next step in optimizing your growth, Schedule a free call today to learn how we can help you manage your VPD and cultivate it confidently. Let us assist you in reaching your full growth potential!
