Top 7 Strategies for Keeping Your Greenhouse Cannabis Mold-Free

Greenhouses are increasingly becoming the go-to solution for cannabis cultivation. They offer the best of both worlds: the natural spectrum of sunlight and the ability to control environmental factors. However, one challenge that persists is the risk of mold contamination. In this comprehensive guide, we’ll explore the top 7 strategies to keep your greenhouse cannabis mold-free, including the types of commercial greenhouses best suited for mold prevention.

1. Choose the Right Type of Greenhouse For Cannabis

Free-standing Greenhouses

Free-standing greenhouses are generally the best choice for smaller operations. They come in various shapes, such as quonset (hoop), gothic, or gable roof shapes. The quonset shape is usually the least expensive and can span widths up to 34 feet. Gothic designs offer higher light transmission and are better at shedding snow, making them ideal for colder climates.


  • Easier to build
  • Less expensive upfront
  • Suitable for smaller operations


  • Less efficient in heating and cooling
  • May require multiple units for expansion, increasing operational complexity

Gutter-connected Greenhouses

Gutter-connected greenhouses are a series of arches connected at the gutter level and are more suitable for larger operations. They offer greater flexibility and are more efficient in terms of heating and cooling.


  • Greater flexibility in design
  • More efficient in heating and cooling
  • Easier to expand


  • More expensive upfront
  • May require more advanced technology for optimal operation

By understanding the pros and cons of each type, you can make an informed decision that best suits your operational needs and mold prevention strategies.

2. Study Your Location

Before you even start building your greenhouse, it’s crucial to study the local climate and environmental conditions. Factors like wind speed, temperature ranges, and humidity levels can all impact your ability to control mold. For instance, areas with high humidity levels may require more advanced dehumidification systems. Similarly, windy areas may necessitate better air filtration systems to prevent contaminants, including mold spores, from entering the greenhouse.

3. Use Advanced Greenhouse Technology

Modern technology has made it easier than ever to control the environment within a greenhouse. Automated control systems can adjust temperature, humidity, and even CO2 levels based on real-time conditions. Positive pressure systems can help keep unfiltered air from entering the greenhouse, reducing the risk of mold contamination.

Key Technologies:

  • Automated Control Systems: These systems can control multiple environmental factors, making it easier to maintain optimal growing conditions.
  • Positive Pressure Systems: These create a higher pressure inside the greenhouse, preventing unfiltered air from entering.
  • Geothermal Heating/Cooling: This uses the earth’s natural temperature to help control the greenhouse environment, often more efficiently than traditional HVAC systems.

4. Implement Operational Tactics

Thrip Screen

Installing a thrip screen can keep out insects, which are a common source of mold. These screens are usually made of fine mesh and should be installed at all air intake points.

Clean Pad Walls

After each growing cycle, it’s crucial to clean the pad walls with an oxidizing agent. This eliminates any lingering mold spores and prepares the greenhouse for the next crop.

Distance from Walls

Keeping plants at least 10 feet away from the pad walls minimizes the risk of mold spores reaching them. This is especially important in larger greenhouses where air circulation may not be as effective near the walls.

5. Plan Your Harvest

The way you plan your harvest can also impact mold growth. Flipping the entire greenhouse at once allows for thorough cleaning, reducing the risk of mold spores lingering and contaminating the next crop. A continuous harvest, on the other hand, can allow mold and other contaminants to spread from one plant to another, making it harder to control the environment.

6. Control Temperature and Humidity

Temperature and humidity are two of the most critical factors in mold growth. By controlling these effectively, you can significantly reduce the risk of mold. One effective strategy is to open shade curtains slowly in the morning. This prevents temperature inversion and condensation, which can cause water droplets to fall from the ceiling, creating a breeding ground for mold.

7. Use AirROS Systems for Mold Prevention

AirROS systems offer a unique and effective solution for mold prevention in greenhouses. Operating at safe levels of 30ppb or lower of ozone and 60-90ppb of gas-phased (dry) Hydrogen Peroxide, AirROS systems can be placed inside a greenhouse 24/7, meeting OSHA standards. The combination of ozone and hydrogen peroxide creates trioxidane, a highly effective compound for surface treatment that kills pathogens without harming the plants, terpenes, flavor profiles, or potencies.

white spots on cannabis leaves

Mold can be a significant challenge when growing cannabis in a greenhouse, but it’s a manageable one. By choosing the right type of greenhouse, using advanced technology, implementing smart operational tactics, and utilizing AirROS systems, you can significantly reduce the risk of mold in your greenhouse.

Ready to take the next step in ensuring a mold-free greenhouse for your cannabis cultivation? Implement these strategies today and experience the difference it can make. Your plants—and your peace of mind—will thank you.


  1. Selecting & Building a Commercial Greenhouse – UMass Amherst
  2. Tips to Prevent Mold in Greenhouse – DryGair
  3. Reducing Mold and Fungus in Greenhouses – BC Greenhouses
  4. Greenhouse Mold – Growing Spaces

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