table of contents

Introduction to Mycelium Pinning

This is what mushroom pins look like

Mycelium pinning is a crucial stage in the mushroom cultivation process, marking the transition from vegetative growth to the formation of fruiting bodies. Understanding this stage is essential for anyone interested in growing mushrooms, as it directly affects the quality and yield of the harvest. In this comprehensive guide, we will explore the process of mycelium pinning, its importance, and factors that influence it, as well as tips and techniques to optimize your mushroom growing experience.

The Mushroom Pinning Process: A Visual Guide

Identifying Primordia and Early Mushroom Pinning

Mycelium pinning, also known as primordia formation, is the stage when the mycelium starts to differentiate and form tiny, initial structures called pins. These pins eventually develop into mature fruiting bodies or mushrooms. Early mushroom pinning can be identified by the appearance of small, white, or brownish protrusions on the surface of the substrate.

Primordia vs Mushroom Pins: What's The Difference?

Primordia and mushroom pins are almost the same thing and some people use it interchangeably. That being said, those two words refer to slightly different stages of the early fruiting process. Here's the difference:

Primordia is a slightly earlier stage in the mushroom fruiting process. It's the absolute first stage at which hyphae starts to change and form a different structure that does not like like mycellium. Those are the little balls that you'll find in your substrate before pins start developing.

Pins are at a later stage, they are usually more elongated and no longer ball-shaped. Pins also start to develop a cap -although these can be unnoticeable in some mushroom species.

How Long from Primordia to Fruit

The time it takes for primordia to develop into fully-grown fruiting bodies varies depending on the mushroom species and environmental conditions. Generally, it can take anywhere from a few days to a couple of weeks for the pins to develop into mature mushrooms.

How Long from Pinning to Fruiting

Once pins have formed, the duration from pinning to fruiting typically ranges from 5 to 12 days, depending on the mushroom species and growing conditions. Maintaining optimal environmental factors during this period is essential for healthy fruiting body development.

Factors Influencing Mycelium Pinning

Air Exchange and CO2 Levels

Proper air exchange and maintaining optimal CO2 levels in the grow room are crucial for mycelium pinning. High CO2 levels can inhibit pin formation, while insufficient air exchange can lead to poor pin development and fruiting. Aim for 3-5 air exchanges per hour to maintain the ideal CO2 concentration for pinning.

The Impact of Humidity Levels on Pinning

Maintaining proper humidity levels is essential for successful pinning and mushroom development. Aim for relative humidity (RH) of 90-95% during the pinning stage, as lower humidity can cause pins to dry out and abort, while higher humidity can lead to mold and bacterial contamination.

Mushroom Species-Specific Pinning Considerations

Different mushroom species have varying pinning requirements and preferences. For example, oyster mushrooms prefer higher humidity and more frequent air exchanges, while shiitake mushrooms require a drop in temperature to initiate pinning. Research the specific needs of the species you are cultivating to optimize pinning conditions.

Setting Up Your Grow Room for Successful Pinning

Fruiting Chamber Essentials

A well-designed fruiting chamber ensures optimal growing conditions for mycelium pinning. Essential elements of a fruiting chamber include proper air circulation, temperature control, humidity control, and lighting. Consider using a combination of fans, heaters, humidifiers, and timers to maintain ideal conditions.

Managing Temperature and Light Conditions

Temperature plays a crucial role in mycelium pinning, with most species requiring a drop in temperature to initiate the process. Ensure that your grow room maintains the ideal temperature range for the species you're growing. Additionally, provide a consistent light source with a 12-hour on/off cycle to encourage healthy pin development.

Fresh Air Exchange

As mentioned earlier, proper air exchange is essential for successful mycelium pinning. Fresh air helps maintain ideal CO2 levels, promotes healthy pin development, and reduces the risk of mold and bacterial contamination. Ensure that your fruiting chamber has an adequate air exchange system, such as passive vents or an active fan system, to maintain optimal conditions.

Techniques for Initiating Mushroom Pinning

How to Initiate Pinning in Different Mushroom Species

Different species may require unique methods to initiate pinning. For example, shiitake mushrooms often need a "cold shock" – a sudden drop in temperature – to stimulate pinning, while oyster mushrooms benefit from regular misting and increased air circulation. Research the specific pinning requirements of the species you're cultivating to maximize success.

Tips for Oyster Mushroom Pinning

Oyster mushrooms are a popular choice among home growers for their ease of cultivation and rapid growth. To encourage healthy pinning in oyster mushrooms, maintain high humidity (95% RH), provide regular air exchanges (5-8 times per hour), and expose them to indirect light for 12 hours per day.

Mushroom Growing Kit Options for Easy Pinning

Grow kits are a popular choice for beginners

For beginners or those looking for a hassle-free growing experience, mushroom growing kits are an excellent option. These kits come with pre-colonized substrates and detailed instructions, making it easy to achieve successful pinning and fruiting. Research and select a kit designed for the specific mushroom species you're interested in growing. These are the ones I'd recommend:

Troubleshooting Common Mushroom Pinning Issues

Mushroom Pins Not Forming: Causes and Solutions

If pins are not forming, it may be due to inadequate environmental conditions, such as improper humidity, temperature, or air exchange. Review and adjust these factors to encourage pin formation. Additionally, ensure that the substrate has been fully colonized before initiating fruiting conditions.

Stalled Mushroom Pin Growth: How to Address It

Stalled pin growth can be caused by suboptimal environmental conditions or lack of nutrients. Check and adjust temperature, humidity, and air exchange as needed. If the substrate appears depleted, consider adding supplemental nutrients or transferring the mycelium to a new substrate.

Substrate Bruising or Yellowing: Prevention and Remediation

Bruising or yellowing of the substrate is often a sign of excessive handling or stress on the mycelium. Minimize handling and ensure that environmental conditions are optimal to prevent further damage. If bruising is severe, consider isolating the affected area to prevent the spread of potential contaminants.

Optimizing Your Mushroom Growing Process for Maximum Yield

The Importance of Experimentation and Experience in Mushroom Growing

Embrace experimentation and continuously gain experience to optimize your mushroom growing process. Trial and error is a valuable learning tool, as it allows you to discover what works best for your specific setup and the mushroom species you're cultivating. Don't be afraid to test new techniques, substrates, or environmental adjustments to improve your pinning success and overall yield. As you gain experience, you'll develop a deeper understanding of your mushrooms' needs and become more adept at creating the ideal conditions for a bountiful harvest.

Fine-Tuning Fruiting Conditions for Better Pin Development

Continuously monitor and adjust fruiting conditions to ensure optimal pin development. Track changes in temperature, humidity, and air exchange, and adjust as needed to maintain the ideal environment for your mushroom species.

Adapting to Species-Specific Requirements

Be prepared to adapt your growing techniques and conditions based on the specific requirements of the mushroom species you're cultivating. Research and understand the unique needs of each species to ensure a successful and bountiful harvest.


Understanding and mastering mycelium pinning is essential for anyone interested in growing mushrooms. By maintaining optimal environmental conditions, fine-tuning your growing techniques, and learning from the experiences of other growers, you can maximize the yield and quality of your harvest. Happy growing!