VPD table for cannabis: Optimal humidity control in the grow room

The VPD (Vapour Pressure Deficit) chart is one of the most important tools for growers to create the best growing conditions for their plants. Whether you're growing cannabis, vegetables or other plants, the VPD helps you find the right balance between humidity and temperature. These two factors have a huge impact on how well your plants breathe, absorb nutrients and grow.

An optimal VPD value not only promotes healthy growth, but also protects your plants from common problems such as mould, rot and wilted leaves. Especially in cannabis cultivation, an unbalanced VPD can severely stress the plants, which can lead to reduced yields or poor quality. With the right VPD chart, you can ensure that your plants always thrive in the perfect environment - regardless of the growth phase. In this blog, we explain exactly what the VPD is, why it is so important and how you can use it effectively for your grow room.

What is the VPD (Vapour Pressure Deficit)?

The Vapour Pressure Deficit (VPD) describes the difference between the maximum humidity that the air can hold at a certain temperature and the actual humidity present. Put simply, it indicates how "thirsty" the air is for water. This value is crucial because it influences the transpiration behaviour of plants - i.e. the plant's ability to release water through its leaves.

A balanced VPD ensures that the plant loses just the right amount of moisture. If the VPD is too low, the plant cannot transpire properly, leading to excessive moisture and problems such as mould. On the other hand, if the VPD is too high, too much water evaporates from the leaves and the plant dries out or shows signs of stress. This is why it is so important to keep a close eye on the VPD and use a VPD chart to find the perfect balance between temperature and humidity.

How is the VPD value calculated?

The calculation of the VPD-Wertes may seem complicated at first glance, but it is relatively simple if you have the right values to hand. The VPD essentially depends on two factors:

1. Lufttemperatur : The warmer the air, the more water it can absorb.

2. Relative humidity (RH) This value indicates what percentage of the maximum humidity the air can hold at the current temperature is already present.

The VPD formula combines these two values to calculate how much "space" is left for water vapour in the air. This allows you to determine whether your plants' environment is too humid, too dry or just right.

Fortunately, you don't always have to calculate the VPD yourself - VPD tables and Online-Rechner do the work for you. With these tools, you can quickly determine the optimum conditions for your plants by simply entering the temperature and relative humidity. This is a great help, especially in grow rooms, where stable conditions can make the difference between success and failure.

The importance of the VPD table for plant cultivation

A VPD-Tabelle is a practical tool for growers to quickly and easily determine the ideal VPD value. It shows which Temperatur and Luftfeuchtigkeit are optimal for certain plant stages. The VPD plays a central role in cannabis cultivation in particular, but also in other plants such as tomatoes or cucumbers. Each growth phase, whether Keimung , Vegetation or Flower has its own needs, and the VPD table helps you to control them precisely.

Why is this so important? A VPD value that is too low means that the air is almost saturated and the plant can transpire less. This often leads to slower growth and an increased risk of mould. A VPD value that is too high, on the other hand, causes the plants to lose water as they release more moisture than they can absorb, which can lead to stress and even growth disorders.

With the VPD table, you stay in control and can set your air conditioning system, humidifier or dehumidifier so that the plants get exactly the conditions they need for optimum growth.

Optimal growing conditions with VPD tables in cannabis cultivation

At Cannabis-Anbau the use of a VPD table is particularly helpful, as the plant has different needs in each phase. The table gives you a clear overview of which combination of temperature and humidity gives the best results. These values serve as a guideline to ensure that the plants are optimally cared for in each growth phase.

An example of typical VPD values in cannabis cultivation:

- Keimung High humidity (approx. 70-80 %) and low VPD value of 0.4-0.8 kPa .

- Vegetationsphase Medium humidity (approx. 60-70 %) and a VPD value of 0.8-1.2 kPa .

- Blütephase Lower humidity (approx. 40-60 %) and a VPD value of 1.2-1.6 kPa .

The table helps you to keep an eye on fluctuations in temperature and humidity and adjust accordingly. This way you can ensure that your plants always grow in the best environment. Especially in the Blütephase If the risk of mould or dry damage is higher, it is important that you check the VPD values regularly. In this way, you optimise the Quality and yields of your plants.

VPD table for cannabis

At Cannabis-Anbau precise control of environmental conditions is crucial to optimise plant growth and health. The VPD-Tabelle (Vapour Pressure Deficit) helps to find the right balance between Temperatur and Luftfeuchtigkeit can be found in every phase of the plant cycle. Each phase - from the Keimung up to Flower - requires specific conditions in order to optimise Transpiration and nutrient absorption.

Here is an overview of the ideal VPD-Werte , temperatures and humidity ranges for each phase of the plant cycle:

Detailed VPD table for cannabis

Explanation of the phases

1. Propagation (germination) : In the germination phase, the plants require a very high Luftfeuchtigkeit (75-85%) and low VPD-Werte (0.1-0.3 kPa) to ensure that they absorb sufficient moisture without drying out.

2. Early growth phase : The VPD-Werte rise to 0.4-0.8 kPa in this phase. This promotes the Transpiration and supports root development while the humidity remains high (75-80%).

3. Late growth phase : In this phase, the humidity is further reduced to 55-75% to prepare the plant for Flower. Ideally, the VPD value is between 0.7 and 1.0 kPa in order to minimise the Wachstum to maximise.

4. Early flowering phase : In the flowering phase, the VPD-Werte to 0.8-1.2 kPa. Reduced humidity (50-75%) and a stable temperature support the Blütenwachstum while mould formation is avoided.

5. Late flowering phase : At the end of the flowering phase, the VPD-Wert further to 1.2-1.6 kPa. The humidity drops to 40-65% to reach the Blütenreife and minimise the risk of mould.

Sanlight and LED lighting: influence on the VPD

Choosing the right Beleuchtung also has a major influence on the VPD value in your grow room. Moderne LED-Lampen such as from Sanlight generate less heat compared to traditional lighting systems. This means that they do not increase the air temperature as much, which has a direct effect on the VPD.

If you have less heat from the lamps, you must use the Luftfeuchtigkeit in the room in order to achieve the optimum VPD. Too little heat can lower the VPD, resulting in excessive humidity - an ideal breeding ground for mould. On the other hand, LED lamps are energy efficient and give you more control over the climate in the room.

With the right VPD table and good LED lighting, you can use the Mikroklima in your grow room to get the best out of your plants. Especially in the flowering phase, the combination of uniform lighting and an optimum VPD value can help to optimise the Flower density and quality to increase.

Tips for using the VPD table in the grow room

To get the most out of the VPD table, there are a few simple tips to help you create ideal conditions in the Grow-Raum to create:

1. Regularly check the values : Regularly monitor the Temperatur and Luftfeuchtigkeit in your grow room. Small fluctuations can quickly change the VPD and influence the growth of your plants.

2. Ensure air circulation : Good ventilation is crucial to maintain a constant temperature and humidity. Ventilatoren and Abluftsysteme help to distribute the air evenly and prevent mould growth.

3. Adjust lighting Use lighting that suits your setup. As already mentioned, LED-Lampen like the one from Sanlight have the advantage that they emit less heat, making it easier to control the VPD.

4. Use climate control : A Luftbefeuchter or Luftentfeuchter can help you to precisely control the humidity in the room. Combined with a VPD table, you know exactly when you need to adjust the humidity.

5. Technical aids Use digital measuring devices or apps to calculate the VPD value and control your conditions automatically. These tools take a lot of work off your hands and ensure that you don't miss any important adjustments.

With these tips, you can ensure that your plants always thrive in the best conditions - from seed to harvest.