Yes, you can grow mushrooms in a greenhouse, but the process requires significant modification because fungi thrive in an environment that is the direct opposite of what a conventional greenhouse is designed to provide. A standard greenhouse maximizes sunlight and heat for plant photosynthesis, creating conditions hostile to most cultivated mushroom species. Mushrooms are fungi that require specific, dark, cool, and extremely humid conditions to develop their fruiting bodies. Converting a greenhouse involves transforming a warm plant habitat into a shaded, climate-controlled fungal fruiting chamber.
The Environmental Mismatch: Why Greenhouses Pose a Problem
A typical greenhouse environment actively works against the requirements for successful mushroom cultivation, particularly in the control of light, temperature, and humidity. Greenhouses capture and amplify solar energy, resulting in internal temperatures that quickly exceed the ideal range for most fungi. Common species, such as Oyster and Shiitake, require a temperature range generally between 55–75°F (13–24°C) for fruiting, which a glass or polycarbonate structure can easily soar above.
High light transmission is detrimental, as direct sunlight can kill the delicate fungal mycelium, the vegetative part of the fungus that colonizes the substrate. Mushrooms do not photosynthesize and require only very low, indirect light, or darkness, to trigger fruiting. Standard greenhouses also struggle with maintaining the consistently high relative humidity necessary for mushroom development. Fungi require atmospheric moisture typically between 80–95% to prevent the rapid dehydration of the substrate and the developing mushrooms.
The constant air exchange and natural venting used in plant cultivation often result in fluctuating humidity, which mushrooms cannot tolerate. Furthermore, the air quality needs are inverted compared to plants. Plants consume carbon dioxide (CO2) and produce oxygen, but fungi consume oxygen and produce CO2. Standard greenhouse ventilation is not optimized to manage the CO2 buildup from a dense mushroom crop, which can lead to elongated, malformed caps and stems.
Essential Greenhouse Modifications for Mushroom Cultivation
The conversion of a greenhouse into a suitable environment centers on actively controlling light, humidity, and airflow. To manage high light levels, growers must apply heavy shading, often using 90% or higher blockage shade cloth over the exterior or by painting a white shading compound onto the glazing material. This modification turns the light-maximizing structure into the dim environment necessary for fungal growth.
Temperature control demands the installation of active cooling systems, such as evaporative coolers (swamp coolers) or air conditioning units in warmer climates. These systems are necessary to maintain the internal temperature within the narrow optimal range required for fruiting, especially during warmer months. The cooling system must work in tandem with a robust airflow and ventilation system to manage temperature and prevent overheating.
Maintaining the necessary high humidity requires specialized equipment, such as ultrasonic humidifiers or fine-mist fogging systems, rather than simple hand-misting. These systems atomize water into a fine vapor to maintain relative humidity consistently between 80% and 95% without soaking the substrate. Proper air exchange must use exhaust fans equipped with timers and CO2 sensors to remove the carbon dioxide produced by the mushrooms without excessively dropping humidity. This balanced ventilation is a significant challenge, as fresh air is needed to encourage proper mushroom formation, but it must be introduced gently to avoid drying out the environment.
Selecting Mushroom Species for Greenhouse Success
Choosing the right mushroom species is a practical step that can ease the challenges of environmental control within a modified greenhouse. Species that are naturally hardier and more tolerant of slightly less-than-perfect conditions are the best candidates. Oyster mushrooms (Pleurotus species) are highly recommended because they have a fast growth cycle and are relatively forgiving of temperature variations.
Certain strains of Shiitake (Lentinula edodes) are also suitable, particularly those adapted for warmer climates, though they may require precise temperature drops to reliably trigger fruiting. Another excellent choice is the Almond Agaricus (Agaricus subrufescens), which naturally thrives in warmer temperatures, making it a good fit for an environment that might struggle with cooling.
Conversely, sensitive species, such as Enoki (Flammulina velutipes), which require hyper-specific, cold temperatures and high CO2 levels to achieve their signature long-stemmed appearance, are best avoided. These varieties require precise, often commercial-grade, climate control that is difficult to achieve efficiently in a repurposed greenhouse structure. Starting with a robust and adaptable species significantly increases the likelihood of a successful harvest.