Proper humidity and temperature levels are crucial to creating an optimal environment for microgreens and streamlining their growth. However, most microgreen growers don’t understand how to control, decrease, or increase humidity and temperature levels to ensure the best possible development.

Online research shows that 40% to 60% humidity levels are ideal for growing microgreens. On the other hand, if your grow room’s humidity is between 20% and 40%, microgreens will not grow properly, leading to stunted growth, poor development, and eventual death.

How can I raise the humidity in my grow room? Most growers ask this question to optimize the overall environment and ensure microgreens’ growth is up to the mark. The quick answer to this question is:

Install a humidifier, place fans for ventilation, evaporator swamp coolers, and water trays, use propagators, reduce fluorescent lights, group similar microgreens, and add large plants near microgreens to raise humidity levels in the grow room.

Learning the significance of microgreens’ humidity levels is critical to achieving optimal growth and preventing the risk of diseases and death. Today’s article will highlight the importance of humidity in grow room, how low humidity can cause problems, and effective ways to increase humidity levels. Read on!

Why is Humidity Low in My Grow Room?

A grow room comes in various sizes, shapes, configurations, and features. Some grow rooms are portable greenhouses with built-in heating, lighting, temperature, and humidity control devices. In contrast, others do not have these built-in features and require microgreen growers to manually install these devices.

However, installing and managing these devices require in-depth knowledge and experience. Otherwise, low humidity in the grow room means insufficient water vapors in the air space. Therefore, maintaining an optimal amount of water vapors in the air ensures good microgreens’ growth.

You can measure the relative humidity and determine the correct water vapor to air ratio by installing a hygrometer in your grow room. A study in 2016 states that 50% of relative humidity is ideal for plant growth. If the relative humidity level is below 50%, the grow room’s environment will experience fewer water vapors.  

So, we recommend increasing humidity in the grow room at least once or twice a week to prevent wilting, fading, and poor growth. Not using a hygrometer, inappropriate venting techniques, too much airflow, etc., are common causes of low humidity in your grow room.

Is Humidity Important for Growing Microgreens?

Although too much humidity is not ideal for humans because it can increase the risk of mold and mildew, high or low humidity levels can also affect microgreens’ growth in the grow room. Microgreens require a specific humidity level to streamline and complete their growth cycle.

Because all plants, including microgreens, require Co2 from the environment for photosynthesis, they absorb moisture from the air. However, too much dryness in the surrounding environment prevents microgreens from absorbing the optimal quantity of water.

On the other hand, if the surrounding environment has too many water vapors, your microgreens will experience mold growth and other diseases, negatively affecting their development and growth. Increasing humidity in your grow room opens stomata (tiny pores in microgreens that absorb moisture from the air), streamlining the entire photosynthetic process.

However, the low quantity of water vapors in the surrounding environment causes microgreens’ stomata to close and stop photosynthesis. As a result, microgreens do not produce enough food and energy to carry out essential processes. Remember, keeping your microgreens’ stomata open is more critical than maintaining lighting conditions for the micro plants.  

What happens if Humidity is Too Low in Grow Room?

Most microgreen species grow well in an environment with 40% to 60% humidity. However, this depends on the microgreen’s growth stage and the surrounding environment. For example, you must maintain relative humidity levels between 50% and 80% during germination.

Moisture below 50% or above 80% can negatively affect microgreens’ growth, appearance, photosynthesis, and other processes. Therefore, controlling the moisture levels in the grow room is essential. Dry air in your grow room causes your microgreens to lose more moisture.


Dehydration of microgreens is primarily due to dry air, high temperature, and low humidity levels. Too much evaporation at regular intervals can weaken the microgreen’s tissue and cellular structure, causing dehydration, wilting, diseases, and death. Low humidity levels in the grow room can also affect microgreens’ flavor. Sometimes, the flavor changes, causing the microgreens to taste rotten.

Slow Germination

Slow germination is another negative effect caused by low humidity or moisture levels in your grow room. Not enough moisture in the grow room means the microgreens’ seeds will take a prolonged germination period. We recommend keeping the soil moist to prevent slow germination. However, you must not go beyond the appropriate levels and ensure the soil is not too wet.

How Can I Raise the Humidity in My Grow Room?

We have already answered “how can I raise the humidity in my grow room” in the introductory section. So, it is time to delve into details and explain the most effective ways to increase moisture or humidity levels in the “grow room.”

1.    Install a Humidifier Inside Grow Room

Installing a humidifier inside your grow room is one of the most effective ways to raise humidity levels. It is a cutting-edge device or machine that extracts a cool mist and elevates moisture in the grow room. We recommend increasing your humidifier’s moisture levels to 50% or 65%, depending on your grow room’s size, type of microgreen species, and air-to-humidity ratio.

For example, we suggest installing or placing the humidifier on the bottom shelf if your grow room has multiple shelves, such as top, middle, and bottom shelves. The purpose is to maintain optimal moisture levels and prevent the humidifier from directly spraying mist on the lights.

Invest in a high-end humidifier with automation features to control humidity based on the microgreens’ requirements. A manual humidifier with no humidistat may not maintain optimal moisture settings in the grow room because it does not automatically slow down or shut off.

Moreover, Consider the quantity of water a humidifier can hold before purchasing the product. A humidifier with 5-6 gallons of water capacity is ideal for maintaining the desired humidity levels in the grow room.

A high-end humidifier can control airflow, temperature, and moisture levels. On the other hand, if you don’t have the budget to buy a high-end humidifier, you can find a cheaper one and install a separate humidity controller to prevent low moisture levels in the grow room.

Remember, a humidity controller works with intake and exhaust fans, humidifiers, dehumidifiers, and other devices, allowing you to track your grow room’s moisture levels. A premium-quality humidity control has adjustable set points, enabling you to set optimal moisture levels for hours, days, or weeks, depending on microgreen humidity requirements.

2.    Focus on Proper Ventilation

The relative humidity is the ratio of water vapors and air particles in the grow room. Proper ventilation based on the grow room’s size and environment is essential to manage relative humidity for your microgreens. The primary objective of ventilation is an optimal exchange of air between the grow room and the external environment.

So, how to maintain proper ventilation in your grow room. You need to install fans in areas to circulate and distribute air to the growing microgreens. The primary objective of strategic fan installation is to ensure proper air circulation and prevent microorganisms, including bacteria, viruses, and fungi, from affecting the microgreens.

Bear in mind that too much airflow cannot conserve humidity levels at different stages of microgreens’ growth. Therefore, we recommend setting your fans’ at a mild or moderate speed to avoid too much evaporation. Likewise, setting your fans at a medium speed will ensure stomata remain open and receive enough moisture to streamline photosynthesis.

Another advantage of installing fans in the grow room is preventing microgreens’ from dehydration and desiccation. However, avoid installing many fans in the grow room to maintain optimal humidity levels for microgreens. A balanced approach based on the grow room’s size is essential to optimizing the environment for microgreens.

3.    Place Water Trays Near Passive Air Holes

Although you can invest in a humidifier with built-in features and install fans at strategic locations, if you are on a budget, you can look for alternative and affordable methods. One method is placing water trays near passive air holes or air intake tubes.

Placing water trays near passive holes is an efficient, reliable, and cost-effective technique to increase moisture in the grow room and ensure each microgreen plant receives optimal humidity to streamline its growth.

Moreover, you can also place damp sponges near the growth trays. These sponges can extract evaporation particles from the environment due to heat generated by the air conditioner or lighting system.

These sponges capture the evaporative water particles and maintain moisture in the grow room. However, we suggest clean water to create an optimal environment for the microgreens and prevent the risk of bacteria, viruses, and fungi from accumulating on the microgreens’ surfaces.

4.    Install Evaporative Swamp Coolers

Most microgreen growers install lighting systems and air conditioners to speed up photosynthesis. However, these devices can produce heat, causing moisture to evaporate from the grow room.

So, installing evaporative swamp coolers is an excellent solution to maintaining the correct temperature in the grow room by allowing the heat to escape and providing proper airflow to the microgreens.

Likewise, evaporative cooling devices contain water, meaning the air it produces has enough humidity to ensure an optimal, fresh, and growth-rich environment. However, we recommend installing the evaporative swamp coolers with hose hook-up capability, variable speeds, and casters to ensure everything goes smoothly.

5.    Reduce the Number of Fluorescent Lights in Grow Room

Although fluorescent lights play a critical role in optimizing microgreens’ growth by improving photosynthesis, these lights can generate heat and affect the growth room’s relative humidity ratios.

Because most growers install fluorescent lights at the top of microgreens to ensure more photons penetrate these plants and speed up photosynthesis, these lights can close stomata due to increased temperature levels.

The reason is that a fluorescent light’s surface heats up to 100 degrees Fahrenheit or 37.78 degrees Celsius. So, reduce the number of fluorescent lights to prevent heat from accumulating in the grow room. Remember, microgreens require light for photosynthesis, but increased moisture is more important than intense lighting.

6.    Use Propagators for Optimal Germination

Although microgreens seedlings have the ability to germinate, increasing humidity levels in the grow room can streamline the process and ensure better germination. You can achieve this goal through a propagator.

We recommend using a glass or polyethylene sheet to cover the propagator. The purpose is to reduce the risk of low moisture and prevent seedlings from drying. Follow the steps below to optimize the entire process.

  1. Preparing the propagator requires you to find a plastic storage bin
  2. Make sure you choose the storage bin with a lid
  3. Wash the bin with soap and water to ward off microbes
  4. Remove dirt, dust, and debris from the bin
  5. Ensure the storage bin is clear to ensure light reaches the microgreens
  6. Now, add three to four inches of rooting medium to the propagator
  7. Spread the rooting medium evenly across the propagator box or bin
  8. Avoid regular potting soil because it is heavy enough to cause rots
  9. Next, add water to the rooting medium/mix using gentle sprays
  10. Close the lid after adding cuttings
    1. (if you have added too much water to the rooting mix, keep the lid open to evaporate excess water)

7.    Group Similar Microgreen Species

Grouping similar microgreens or adding humidity-loving plants to the grow room can favor microgreens by maintaining optimal moisture levels. For example, snakes, spiders, gardenias, prayer, monstera, nerve, and parlor plums can maintain high moisture levels in the grow room.

However, it would help if you determined the plant’s compatibility with micro greens to avoid potential problems. Likewise, compatible microgreens for grouping include cabbage, cauliflower, sunflower, buckwheat, mustard, chia, and broccoli. You can grow these microgreens in a single container.

8.    Place Large Plants Near Microgreens

Most microgreens growers think placing large plants near micro plants can extract more moisture, air, and nutrients from the environment, preventing microgreens from optimal growth. However, this is a misconception because large plants can help microgreens’ growth and development by evaporating vapors from their system. Unlike microgreens, larger plants have large-sized stomata, evaporating more vapors in the environment and allowing microgreens to absorb more moisture.

Final Words

Common microgreens in the grow room are beets, chard, spinach, quinoa, garlic, chives, leeks, and onions. These microgreens are a rich source of essential nutrients, including iron, zinc, potassium, magnesium, copper, and antioxidants. However, not having optimal moisture levels in the grow room can prevent microgreens from these essential nutrients.

So, low moisture affects the plants, leading to stunted growth and diseases and depriving them of maintaining nutrients. Follow the methods above to raise the humidity in your grow room. Until Next Time!

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