Basic Procedures for Agaricus Mushroom Growing


Did you know that the cultivation of mushrooms dates back to ancient times? Hippocrates, the famous Greek physician, mentioned their medicinal value as early as 400 B.C. However, it wasn’t until the 17th century that mushroom cultivation began to gain momentum. Since then, the art and science of growing mushrooms have evolved significantly.

In this article, we will explore the basic procedures involved in growing Agaricus mushrooms, the most commonly cultivated mushrooms worldwide. We will delve into the various stages of mushroom production, from composting to harvesting, and provide valuable insights along the way.

A Review of Mushroom Growing

Before we dive into the nitty-gritty of mushroom cultivation, let’s understand a few key aspects of these fascinating fungi.

Mushrooms are not plants; they are fungi. Unlike plants, mushrooms cannot use the sun’s energy through photosynthesis. Instead, they derive their nutrients from decaying organic matter in the environment. This organic matter needs to be transformed into a nutrient-rich substrate that the mushrooms can consume. This transformation process, known as composting, is a crucial step in mushroom production.

Making a Composted Substrate

The first step in growing Agaricus mushrooms is preparing a composted substrate or compost. Various agricultural by-products, such as straw-bedded horse manure, hay, or wheat straw, are commonly used as bulk ingredients. These ingredients are mixed with nitrogen-rich supplements like poultry manure or meals, such as soybean meal, to enhance their nutrient content.

To stimulate the composting process, gypsum is added to the mixture, which improves airflow and prevents the straws from sticking together. Composting is a delicate process that requires careful attention to temperature and moisture levels to create an ideal environment for the growth of beneficial microorganisms.

Aerated Phase I Composting

In recent years, advancements in mushroom cultivation technology have led to the development of aerated composting systems. These systems help maintain aerobic conditions throughout the composting process, preventing the growth of offensive odors and optimizing the growth of beneficial microbes.

During Phase I composting, the compost is carefully turned and aerated to promote microbial growth and release heat, ammonia, and carbon dioxide. The temperature of the compost is gradually increased to around 155ºF (70ºC) to ensure the elimination of unwanted organisms and the conversion of complex carbohydrates into a suitable food source for mushrooms.

Phase II: Finishing the Compost

Once Phase I composting is complete, the composted substrate enters Phase II, also known as the finishing stage. The primary objectives of Phase II are pasteurization and the completion of the composting process.

Pasteurization involves subjecting the compost to elevated temperatures (140-150ºF or 60-70ºC) for a specific duration to eliminate potential pests and diseases while preserving beneficial microbes. Additionally, the remaining simple soluble sugars and gaseous and soluble ammonia produced during Phase I are further converted into protein—essential food for the mushrooms.

Growing Systems (Phase II)

After Phase II composting, the fully colonized substrate is ready to be transferred to a growing system. There are three main types of mushroom-growing systems: multizone, single-zone, and bulk pasteurization or tunnels.

In multizone systems, the substrate is filled into boxes or trays, which are then moved from room to room at different stages of mushroom development. Single-zone systems consist of large, stacked beds or shelves within a single room, while bulk pasteurization or tunnel systems involve filling compost into perforated bins. Each system has its advantages and is suitable for different production requirements.

Spawning and Spawn Maintenance

Spawning is the process of introducing mycelia (the vegetative part of the fungus) into the composted substrate. Spawn, which contains pure-culture mycelium, is mixed with the compost during spawning. The mycelia colonize the substrate and form a network throughout the compost, preparing the groundwork for mushroom development.

Spawn maintenance is crucial to ensure the purity and quality of the mycelial culture. Contaminants and abnormal mycelial growth, such as sectoring, can negatively impact mushroom productivity. Therefore, growers must carefully monitor and propagate healthy mycelial cultures.

Pinning and Harvesting

The pinning stage marks the transition from vegetative growth to reproductive growth. Mushroom initials, also known as pins, develop on rhizomorphs (thicker mycelial strands) in the casing layer. These pins continue to grow and develop into mature mushrooms.

Harvesting occurs over a 2-4-day period during flushes or breaks. Mature mushrooms are hand-picked to ensure the best quality and freshness. The timing of breaks and harvesting is carefully managed to optimize yield and quality.

Post-Crop Pasteurization and Spent Mushroom Substrate (SMS)

After each harvest, the spent substrate or compost is steam-pasteurized to eliminate any potential pests or pathogens. This process ensures that subsequent mushroom crops are not affected by contaminants. The pasteurized spent substrate, known as spent mushroom substrate (SMS), can be used as a soil amendment or soil conditioner due to its rich organic matter content.

SMS has various uses, such as spreading it on newly seeded lawns, using it as mulch for turf, or incorporating it into potting mixtures. However, it is essential to weather the fresh spent substrate for a few months to reduce its salt content before using it in gardens or potting mixtures.


Growing Agaricus mushrooms involves a series of complex and precise procedures. From composting to harvesting, each stage requires careful management of temperature, moisture, and environmental conditions. However, with proper knowledge and experience, growers can achieve successful mushroom production and enjoy a bountiful harvest.

So, whether you are a seasoned grower or just starting in the world of mushroom cultivation, these basic procedures will provide you with a solid foundation to embark on your mushroom-growing journey. Happy cultivating!

Related Readings:

  • Atkins, Fred C. 1974. Guide to Mushroom Growing. London: Faber and Faber Ltd.
  • Chang, S. T. and W. A. Hayes. 1978. The Biology and Cultivation of Edible Mushrooms. New York: Academic Press.
  • Lambert, L. F. 1958. Practical and Scientific Mushroom Culture. Coatesville, Pa.: L. F. Lambert, Inc.
  • Penn State Handbook for Commercial Mushroom Growers. 1983.
  • Vedder, P. J. C. 1978. Modern Mushroom Growing. Madisonville, Tex.: Pitman Press.
  • Wuest, P. J., M. D. Duffy, and D. J. Royse. 1985. Six Steps to Mushroom Growing. The Pennsylvania State University Extension Bulletin, Special Circular 268.