Plants grow quickly in warm and humid environments. A greenhouse creates that ideal environment. But this environment is also suitable for growing fungi and plant diseases.
If the moisture is high, harmful microorganisms spread quickly. And that’s too harmful for the plants. Dehumidifiers can help to control the humidity. It also keeps the plants healthy.
Let’s explore the benefits of using dehumidifiers in a greenhouse.
How Excess Humidity Can Be the Main Factor of Plant Diseases?
As we mentioned before, plants grow faster in a humid environment. When the humidity rises above 80 to 90 percent, the leaf mold starts to grow. When the relative humidity is this high, moisture collects on plants’ leaves and stems. The fungi grow on the wet plant surface.
Diseases such as Botrytis (gray mold), mildew, and leaf rot often develop when condensation forms on leaves.
The infections spread quickly from one plant to another. You can avoid this issue by keeping the humidity level below 70%. Dehumidifiers help to keep humidity within a safer range.
Prevent condensation of Plants By using Modern Dehumidifiers
The warm, humid air touches the cooler surfaces of the plant. This forms water droplets on leaves and glass panels.
Using dehumidifiers helps to remove the water vapor before it turns into droplets. Maintaining the moisture level keeps the leaves dry. But make sure to place the dehumidifier in the right position.
It’s best to place the units on both sides of a greenhouse. So the center of the greenhouse gets direct airflow to control the humidity level.
According to the research, this type of setup reduces humidity levels from about 89% to nearly 51%. This creates a much drier and healthier environment for the plants.
What is The Role of Vapor Pressure Deficit (VPD)?
Vapor Pressure Deficit (VPD) indicates the difference between the moisture level of the air and the amount that the air actually can hold. The NHS told us that it becomes hard for plants to release moisture through transpiration.
As a result, plants start absorbing nutrients less effectively. Dehumidifiers help to maintain a healthy VPD level. Plants can transpire perfectly and remain healthy.
Energy Efficiency and Moisture Removal
Modern dehumidifiers are three to four times more energy efficient compared to traditional ones. Advanced models can save between 55% to 57%. These advanced dehumidifiers can remove a large amount of moisture.
Dedicated greenhouse-related dehumidifiers can remove 45 to 140 pints of water per day. You can also use smaller suspended dehumidifiers. These units capture moisture near the plant canopy. It helps to create more uniform humidity.
What is the Ideal Humidity for Different Growth Stages of a Plant?
Check out this table to understand the different humidity levels during each stage.
| Growth Stage | Ideal Relative Humidity |
| Seedlings | 70% – 75% |
| Vegetative Stage | 50% – 70% |
| Flowering Stage | 40% – 50% |
Conclusion
For healthy greenhouse production, you need to control the humidity level. If the moisture levels become high, plant diseases can spread quickly. You can prevent condensation or support plant transpiration by using modern dehumidifiers.
It helps to maintain a balanced humidity throughout the growing process of the plants. Create a more efficient greenhouse environment and reduce disease outbreaks.
Greenhouse Dehumidifier Case Study – Prevent Mold in a Tomato Greenhouse
Country: Netherlands
Growers experienced recurring outbreaks of Botrytis (gray mold) and powdery mildew in a commercial greenhouse growing tomatoes. Humidity in excess of 85% with condensation on plant leaves created favorable conditions for diseases to spread quickly between plants. Disease prevention became more difficult, crop yields were lower, and pesticide usage increased.
The Greenhouse Solution… They installed commercial dehumidifiers on both sides of the greenhouse growing area. Humidifiers were evenly spaced to ensure consistent airflow across the entire plant canopy.
Precision humidistats were deployed to track relative humidity and maintain consistent RH levels between 50–60%, ideal for tomato plants during vegetative growth.
Dehumidifiers Installed:
Condensation was managed by maintaining RH between 50–60%
After just two weeks humidity levels were lowered enough to see:
- Leaf surfaces were dry, helping prevent plant fungi.
- Gray mold outbreaks decreased by greater than 70%.
- Plants could effectively transpire and absorb nutrients due to optimal VPD.
- Energy-efficient models cut operating costs by over 50% compared to previous units.
… Results You Can Grow!
Lower humidity allowed for healthier plants, less chemical spraying, and improved yield.
Greenhouse Dehumidification Case Study – https://www.researchgate.net/publication/6418010_Biological_control_of_Botrytis_gray_mould_on_tomato_cultivated_in_greenhouse#:~:text=Before%20fruit%20setting%2C%20the%20plots,obtaining%20high%20quality%20tomato%20fruits.
Dehumidifier FAQs –Greenhouses
Why can high humidity levels damage plants?
Ans. Mold, mildew and leaf rot thrive in humid conditions. Diseases like fungi are passed by water droplets that form on plant leaves and travel from one plant to another.
How do dehumidifiers help prevent crop diseases?
Ans. By extracting water vapor from the air and maintaining RH levels below 70%, dehumidifiers help keep leaf surfaces dry and minimize risk of contamination.
How does Vapor Pressure Deficit (VPD) affect greenhouse crops?
Ans. VPD refers to the amount of moisture in the air compared to how much moisture air can hold at a specific temperature. If the VPD is in the correct range, plants can release moisture (transpire) and consume more nutrients from the soil.
Where should dehumidifiers be placed in my greenhouse?
Ans. Ideally, placing dehumidifiers on both ends of the greenhouse will promote adequate airflow and humidity control. You can also place smaller units near the plant canopy that are suspended from the ceiling to help capture moisture where it forms the most.
What humidity level is best for my plants?
Seedlings thrive at 70–75% RH.
Vegetative growth does well between 50–70% RH.
Keep humidity levels between 40–50% RH when plants are in the flowering stage.
Are commercial dehumidifiers energy efficient?
Yes! Newer models are capable of extracting 45–140 pints of water per day from the air and use 55–57% less energy than older models.
