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How to Maintain Optimal Nursery Humidity in a Greenhouse

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Maintaining proper humidity levels in a greenhouse nursery is critical to plant health and growth. Too much or too less humidity can lead to stunted growth, disease, and even death. Following these tips will ensure your plants will thrive with optimal nursery humidity.

The Importance of Humidity in a Greenhouse Nursery

Humidity is a measure of the amount of water vapor present in the air. In a greenhouse nursery, maintaining optimal humidity levels is critical for the following reasons:

a. Plant Transpiration: Humidity directly affects plant transpiration, which is how plants release water vapor into the air. Transpiration is critical for nutrient uptake, cooling plants, and maintaining turgor pressure (the internal pressure that keeps plant cells rigid). In low humidity levels, transpiration rates increase, causing water stress and reduced growth. In humid climates, transpiration rates decrease, resulting in reduced nutrition uptake and potential disease outbreaks.

b. Photosynthesis: Humidity affects the rate at which plants produce chemical energy from light. Insufficient humidity levels can adversely affect photosynthesis, leading to stunted growth and reduced yields.

c. Pollination and fruiting: For many plants, humidity is a critical factor in the Pollination and fruiting phases. Low humidity can lead to poor Pollination, while high humidity can cause fruit rot and other diseases.


The Relationship between Temperature and Humidity

In terms of humidity, relative humidity (RH) relates to temperature, which can be misleading. Since warmer air can hold more moisture, relative humidity decreases with temperature while water content remains the same. When the temperature rises by 20°f, the air can hold twice as much water and half as much relative humidity, for example.

This relationship needs to be considered when managing humidity levels in greenhouse nurseries.

Dew point temperature is crucial because it indicates the temperature at which water will condense from humid air. Too much moisture in the air concentrates on surfaces at or below the dew point, starting with pipes and doorknobs and ending with plants.

If the relative humidity in a greenhouse is 85% and the temperature is 60°F, condensation will occur when the leaf temperature drops below 55°F. Whenever the leaf temperature is 1 degree below the air temperature at 95% relative humidity and 60°F, condensation occurs. It is important to monitor and control humidity levels for healthy plant growth.

Know the Ideal Humidity Range for Your Plants

Knowing the ideal humidity range for a particular plant is essential. Most plants thrive at 80°F (27°C) and 80% humidity. There are plants that prefer lower humidity levels, like succulents, while others require higher humidity, like tropical plants. To ensure healthy growth, research the ideal humidity range of plants.

How to Reduce Humidity

A well-drained floor, proper watering, and plant spacing are essential. Heating the plants, moving air, and removing moisture are also effective ways to reduce humidity levels.

Humidity control can be challenging, but there are some cost-effective solutions. Limit the amount of water used and only water when necessary. Avoid watering the plants at night.

Water left on the floor or on plant surfaces evaporates, increasing humidity levels and reducing the energy available to keep the greenhouse warm. By carefully managing water usage, growers can maintain optimal plant moisture levels without sacrificing energy efficiency.

To prevent excess water from accumulating on the floor, water the plants adequately at the right time. Unfortunately, poor air circulation causes moisture to be trapped within plant canopies, which generates high humidity levels.

To improve airflow, it is recommended to space the plants sufficiently and use mesh benches. Another effective method is to use adrip irrigation system or soaker hose to deliver water to the roots where it is needed most.

In a greenhouse nursery, the presence of weeds can affect humidity levels. Weeds can hold water in their leaves and release it through transpiration, causing high humidity. Therefore, to maintain optimum humidity levels, keeping the greenhouse floor well-drained and free of weeds is essential.

To prevent condensation on the foliage, it is recommended to provide bottom heat to improve air circulation within the plant canopy. Rising warm air creates a breeze around the plants, preventing stagnant air pockets. Plus, bottom heat helps keep plant surfaces warm, reducing the risk of condensation and potential fungal growth.

A practical method of reducing humidity is wetting agents, which can be applied by spraying the interior surfaces or incorporating them into the glazing material of poly greenhouses. This help prevent moisture from condensing on the glass and forming droplets that could harm plants. Instead, the water will run off the eaves or foundation, keeping the plants safe and healthy.

One way to regulate the amount of solar energy reaching the crops is by using shade cloths that can be rolled out over rails. However, choosing the right shade of material with a weave that suits the climate is essential.

A looser weave can help address excessive humidity, while a tighter weave can trap moisture and temperature. Additionally, radiant cooling can prevent a sudden drop in temperature overnight and reduce stress on plants in colder climates.

Buy a Quality Humidity Monitor

Purchasing a quality humidity monitor is the first step in maintaining optimal nursery humidity in your greenhouse. This device will allow you to accurately measure the humidity level in your greenhouse and adjust it as needed.

These instruments measure relative humidity (RH), Water content in air compared to maximum moisture content can hold at a given temperature. Hygrometers are available in various types, such as mechanical, electronic, and hygrometer devices, to suit different budgets and needs. Look for displays that are easy to read and provide accurate readings. Some monitors even have alarms that alert you if the humidity level falls outside the desired range. Choosing a quality humidity monitor ensures your plant growth.

Use Proper Ventilation to Control Humidity

Proper ventilation is the crucial and primary method of maintaining optimum nursery humidity in your greenhouse. Without adequate ventilation, humidity can build up and cause plant problems.

Ensure your greenhouse has sufficient vents and fans for good air circulation, which can release excess moisture and maintain proper humidity levels. A balance between ventilation and heating is critical to avoid rapid fluctuations in temperature and humidity. By using good aeration techniques, you can ensure your plants get suitable water for healthy growth.

To achieve this, it is recommended to cycle ventilation and heating 2 to 3 times per hour in the evening and early morning. The time it takes to change air depends on factors such as fan size and usage.

In some cases, air exchange takes only 2-3 minutes, while natural ventilation may take 30 minutes or more. To regulate the humidity, it is recommended to use fan to circulate air and a heater to increase the temperature.

Effective use of heating and cooling systems can help maintain desired humidity levels. For example, a heating system can be used on cool nights to increase the air temperature. However, essential to ensure that the fans and heating system are not running at the same time to prevent the risk of fumes being drawn into the greenhouse. To avoid this, set a clock to start the fan for a few minutes before turning on the heater, and possibly relay to lock out furnace or boiler until fan turns off.

Consider Using a Humidifier or Dehumidifier

If your greenhouse is in a humid climate, you may need a humidifier or dehumidifier. Humidifiers add moisture to the air and prevent plants from drying out. Dehumidifiers remove moisture and prevent mold and mildew growth in humid environments.

Monitor humidity levels regularly and adjust your equipment to keep your plants in perfect balance.

Use a Dehumidifier

To control humidity, a dehumidifier is also an efficient solution. Investing in a quality dehumidifier explicitly designed for greenhouses will help regulate humidity levels and improve air circulation, ensuring optimal growing conditions for your plants.

To achieve this goal, many greenhouse owners opt for a dehumidifier. Keeping warm air in place during winter is easy with these closed systems that draw no air from outside. Most dehumidifiers come with a humidistat, so humidity levels can be monitored and adjusted easily. And dehumidifiers normally use refrigeration or heat pumps to remove moisture from the air so plants can grow properly.

Monitor and Adjust Humidity Levels Regularly

Regular monitoring and adjusting levels are crucial to maintaining optimal nursery humidity in a greenhouse. For example, if the air feels stuffy and your plants turn brown, it could indicate too much moisture. Another indicator is whether the water is left in the plant tray for a long time. Monitoring and regulating the humidity level in the greenhouse is essential to prevent these problems.

In dry climates, low humidity can cause roots to dry out, leaves to wilt or even dry out, and plants to droop.

So misting, using humidifiers, and even placing water pans near plants need to be done to add humidity.

Humidity levels fluctuate with higher levels seen during the summer and rainy seasons. You shouldn't rely solely on your senses to determine humidity levels. A hygrometer or hygrostat is needed for optimal growing conditions. Check humidity with a hygrometer.

Add ventilation or a dehumidifier if the humidity is too high. A humidifier or water pan can add moisture to the air if the humidity level is low. Plant growth and mold prevention depend on humidity levels.


1. Why is it important to maintain proper humidity levels in a greenhouse nursery?

Maintaining proper humidity levels in a greenhouse nursery is critical to plant health and growth. Too much or too little humidity can cause stunted plant growth, disease and even death. Ensuring optimal humidity levels will help plants thrive.

2. What are the consequences of improper humidity in the greenhouse nursery?

Improper humidity levels in greenhouse nurseries can have various negative effects on plants. Too much humidity can lead to fungal diseases like botrytis, while too little humidity can lead to dry soil and dehydrated plants. Proper humidity levels are essential for optimal plant growth and health.

3. What are some tips for maintaining optimal nursery humidity?

There are several tips for maintaining optimal nursery humidity, including regular monitoring of humidity levels, proper ventilation, and using a humidifier or dehumidifier when necessary. Also, avoiding overwatering the plants and keeping proper spacing between them will also help maintain optimal humidity levels in your greenhouse nursery.

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