Cultivation Guide

Fruiting period. Pinhead initiation, mushroom pinning and mushrooms growth parameters

STEP 10. Basic principles of pin setting. Fruiting parameters for pinning, primordia formation, and fruit bodies development. Growing problems during fruiting period and how to trigger pinheads

STEP 10. Day 26-33. Pinhead initiation. Growing parameters for Psilocybe Cubensis

In the previous section, we've already made Growbox or MonoTube or Bottle-tek and discussed briefly the necessary conditions for mushroom fruiting.

Now let's figure out how mycelium are going to change further. What factors affect fruiting and yield? What could possibly go wrong?

Mushroom life cycle

The change from the vegetative colonisation period (mycelium growth) to the fruiting period (knots, pins, primordia and mushroom fruit bodies development) is called pinning, pin setting, pinhead initiation, knotting or fructification.

Pinheads and primordia are knots of mycelium that proceed their development into small mushrooms.

Mushroom life cycle
Mushroom life cycle


All species require a set of environmental conditions for pinning. They are quite different from the conditions for mycelial growth. Mushroom grower should understand the basic principles of pinning process and control changes.

Pinhead initiation in nature depends on climate conditions and seasons of the year.

In temperate and continental climates most mushrooms fruit during cool rainy spring and autumn. In tropical and subtropical climates mushrooms fruit during the rainy season, Psilocybe Cubensis particularly.

The fruiting period ends when the season changes and environmental conditions become too dry, too hot, or too cold. Then mycelium goes dormant, create mycelium network underground and wait for better time. Mycelium wake up for fruiting when the humidity rises and temperature is suitable for fruiting.

Unfavorable conditions is the best time to expand mycelium network, absorb nutrients and restore energy reserves. As soon as tropical rains start again and temperature decrease these reserves are used for supporting new mushroom development

Basic principles of pin setting

Mushroom fruiting indoor response to the same conditions that trigger fruiting in the wild. Most of mushroom species require a few basic fruiting conditions:

Fresh air exchange (FAE) is a main trigger for mushroom fruiting indoor

Lower temperature than optimal for colonisation period in incubator. Usually, a drop in temperature is accompanied by rain in nature and humidity level increasing

High relative humidity is necessary for pins and normal fruit bodies development

High evaporation rate from top layer of mushroom cake. This create proper microclimate, maintain high humidity and one of the triggers for pinhead initiation

Light. Although mycelium doesn't need the same light as plants, however photosensitive species require light for pin setting and mushroom metabolism.

🔴 Pinning and mushroom development proceed if all these factors coincide!

Changing any of these factors can slow down or stop growing process at all. Therefore, grower should control all fruiting conditions in the fruiting chamber (Growbox, MonoTub, Shoeboxes, SGFC, Martha tent etc) during this extremely important period

Fruiting parameters for Pinning and Primordia formation

After placing mushroom cakes in the fruiting chamber for the first 5-10 days the mycelium seems like stop growing at all. It will cover slowly the loosely occupied areas of the substrate. But these will be white new mycelium with an accompanying pleasant mushroom smell.

The first 2 weeks control the constant microclimate in your fruiting chamber!

❇️ Optimum air temperature in the growbox is +21°..+23°C or 70-74°F

The permissible range is +20°..+25°C or 68-77°F. At the lower limit start and growth may slow down. On the top, there is a risk of activating pathogens and mycelium can switch back to the vegetative phase and provoke overlay. Keep in mind mycelium itself heats up during the growing process. Temperature in the substrate will be 1-2° higher.

🔴 Recommended article: Overlay and Stroma in mushroom cultivation

At this point, it will be sufficient to continue cultivation at room temperature. Of course, it depends on the temperature in your home. In the harsh winter months heating may be needed (the same as for the incubator). During summer months, it can be too hot and and you'll need cooling/air conditioning.

Control and measure temperature with an ordinary thermometer.

Thermometer for growbox
Thermometer for growbox

Shroomok's Choice on Amazon:

2-in-1: Simple Digital Thermometer and Hygrometer - C° or F° - 1/2 Pack - $6.99

Bluetooth Digital Hygrometer, Thermometer with Remote App - $11.04

2-in-1: Professional Digital Hygrometer, Thermometer - $17.99

❇️ Relative humidity (RH) 95-100%

To maintain required humidity level spray the walls of the growbox 1-2 times a day. Use spray bottle. Never pour or spray water directly on the mycelium and mushrooms.

Control cover layer of mushroom cake. It should be moist.

You can use humidifier or misting fogger. It can be programmed according to the intensity and frequency of spraying to maintain a constant humidity in the range of 95-100%. Use hygrometer or 2-in-1 hygrometer with thermometer to measure the relative humidity level. If there is no hygrometer condensation on the walls of the growbox is your simplest and most reliable sensor.

Fogger for growbox
Fogger for growbox

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Portable Humidifying Unit - 0.7 L - Light and Auto Shut-Off - $29.99

Misting System, Fogger Humidifier Mister - 4L Tank - $38.99

Professional Humidifier/fogger with Extension Tube - 4L Large Tank - $42.99

Professional Humidifier Double Extension Tube, 2 in 1 Joint - 2.2 L Tank - $45.99

Professional Humidifier, Fogger for GrowBox - 2 L Tank - $45.99

❇️ Fresh air exchange (FAE) and CO2 level no more than 600-800 ppm

As you know mushrooms breathe oxygen and emit carbon dioxide. After lowering the temperature, the mycelium will adapt to the new conditions, the growth of the mycelium will slow down and it will emit a little less carbon dioxide until fruiting "turns on".

But at this stage, it is necessary to ventilate the growbox 3-5 times a day. It is enough just to open the growbox for 3-5 minutes and make a few light strokes of the lid or cardboard over the cakes. The smaller the growbox and the more cakes, the more often your mushrooms need fresh air exchange (FAE).

Lack of oxygen provoke cloudy fluffy, cottony mycelium and at last overlay.

🔴 Recommended article: Overlay and Stroma in mushroom cultivation

❗️ Contaminants mostly prefer stagnant air, while mushroom mycelium prefer fresh moving air. There is one more reason why you should provide FAE.

You can use an aquarium air pump for this on a regular basis

Aquarium air pump for automatic FAE (180 L/hour)
Aquarium air pump for automatic FAE (180 L/hour)
Aquarium air pump for growbox
Aquarium air pump for growbox


There is an aquarium stone at the end of the air pump hose, which must be dipped into water. In this way we filter incoming air and maintain humidity automatically.

Growbox with connected air pump for FAE and humidification
Growbox with connected air pump for FAE and humidification

Shroomok's Choice on Amazon:

Adjustable Oxygen Pump for 20-100 Gallon - 2 Outlets - $15.89

Quiet Oxygen Pump for 20-100 Gallon - 2 Outlets - $16.49

Air Pump with Dual Outlets - up to 80 Gallon - $16.49

Powerful Air Pump - for 20-200 Gallon - 2 Outlets - $21.89


❇️ PC fan/cooler for FAE in growbox or monotube. Size 60-120 mm is okay, it's not essential for this purpose:

Silent Computer Cooling Fan - 80/120 mm - 1 Pack - $4.99

Ultra Quiet Blue LED Fan Cooling - 80/92/120 mm - 1 Pack - $4.49

12V DC Computer PC Fan, 2000 RPM - 60/80/90/120 mm - 2 Pack - $12.99

❇️ CO2 detector or all-in-one Air Quality Monitor

Can be used for measuring carbon dioxide level, relative humidity and temperature.

Digital carbon dioxide detector
Digital CO2 detector

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3-in-1: CO2 Detector, Temperature, Humidity - $38.97

3-in-1: Portable CO2 Detector, Temperature, Humidity - LCD Display - $48.99

Air Quality Monitor: CO2, Temperature Humidity - NDIR Channel Sensor, Rechargeable Battery - $71.99

Professional 6-in-1: CO2 Detector, Air Pollution, Temperature, Humidity - $79.99

3-in-1: CO2 Meter, Temperature, Humidity; USB Power & Battery - $93.45

3-in-1: CO2, Temperature, Humidity, Tabletop & Wall Mountable - $101.99

Smart Home - All-in-One - Radon & Air Quality Monitor - $194.60

❗️For a rough comparison normal outdoor CO2 level is 400-450 ppm. 600-800 ppm is the CO2 level in unventilated room where several people breathe.

❇️ Light 12 hours on/off cycle

Mushroom species that require light to form pins are considered photosensitive. Although light is not necessary for the induction of fruiting in fungi, some spectra have been found to be stimulating for the initiation of pins and are essential for the normal development of the fruiting body.

For example, Psilocybe Сubensis and Panaeolus are such photosensitive species.

🔬 A thorough investigation on the photosensitivity of Psilocybe Cubensis can be found in a master's thesis by E.R. Badham (1979). His work reinforces the conclusions of other researchers working with the Basidiomycetes: more pinheads are initiated upon exposure to blue and ultra-violet light with distinct peaks at 370, 440 and 460 nanometers

🔬 Badham showed that light stimulation at these wavelengths for as little as half a millisecond per day caused primordia to form. In contrast, red, infra-red and green light having wavelengths greater than 510 nanometers were ineffective

🔴 Natural light is suitable, but only diffused soft light. Avoid direct sunlight!

The optimal lighting cycle for psilocybin mushrooms during the pinhead initiation is 12 on/off cycle. Light should be white-blue spectrum (~435-480 nm) or use fluorescent light 6500k lux power.

RGB LED Lamp for growbox
RGB LED Lamp for growbox


Diode LED lamp (cold white light 6500k) is suitable. No need to use powerful lamps for plants. Light is only an additional stimulant and sets the direction of mushrooms growth.

Light for growbox
Diode LED lamp for growbox
Light for growbox
Light for growbox

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LED RGB Color Changing Light Bulb - $9.99

Desk Lamp with Flexible Gooseneck - Portable, Touch Control - $15.78

LED Light, RGB Color Changing, Waterproof - 3 Pack - $14.27

Desk Gooseneck Magnifier Lamp - Metal Large Clamp - Black - $25.98

LED Desk Lamp, 1 USB Charging Port, 2 AC Power Outlet - Black - $26.99

LED Desk Lamp with Wireless Charger - 5 Lighting Modes - White/Black - $24.99

LED Floor Lamp - 4 Color Temperatures, Adjustable Gooseneck - $39.99

❇️ To improve your growing process and make automated air conditions monitoring in growbox you can use different sensors, timers and all sorts of gadgets. It's up to you. The sky is the limit!

Great thing to use is Smart Plug, so that you can connect all your devices with Remote Control that helps to be informed and change growing conditions from anywhere! Most of them are compatible with Alexa, Echo & Google Home.

Shroomok's Choice on Amazon:

Smart Plug, WiFi Socket - 1/4 Pack - $14.99

Smart Plug, Smart Home - 2 Pack - $16.99

Smart WiFi Heavy Duty Outdoor/Indoor Outlet, Timer - 3 Outlets - $19.99

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Smart Plug Bluetooth - A Certified - 4 Pack - $19.97

Pinning (knotting) and primordia examples

All this meditation take up to 2 weeks. As a rule, the first flush of fruiting starts on the 7-12th day.

During the first days in the growbox it seems like mycelium completely stop growing. It's okay, because mycelium needs some adaptation period to new conditions. It can form new small threads or small clouds.

First days of fruiting period
First days of fruiting period

In the first stage (after 7-10 days) you can notice how the mycelium thread are woven into small balls.

Pinhead and primordia examples
Pinhead and primordia examples

At the second stage (after 7-14 days) nodules are formed from these small snow-white balls. These are the very pins (pinheads). Then pins are transformed into primordia, which continue its transformation into fruit bodies — full- grown mushrooms.


Pins and primordia formation can be faster. In the photo below, the 28th day after inoculation and only 4 days in the growbox. You can see small pins and some primordia on the mushroom cake. Although the mycelium didn't cover the entire casing layer tightly, in fact, such mycelium (rhizomorphic type) is ideal!

Growing magic mushrooms. Psilocybe Cubensis (Brazil strain). 28 days after inoculation
Psilocybe Cubensis Brazil (cake 1). 28 days after inoculation
Brazil strain. 28 days after inoculation. Cake after cold shock and rehydration before first flush
Psilocybe Cubensis Brazil (cake 2). 28 days after inoculation. Cake after cold shock and rehydration before first flush

The relationship between primordia formation and yield

The pinning and primordia period is extremely important stage. Certain relationships exist between the pinning process and yields:

📍 During the primordia formation period, pinheads for the first and second flush are being generated.

About 60-75% of the total yield is normally harvested from the first two flushes. That's why the first 7-14 days in growbox for pinhead initiation are the most critical in the growing of mushrooms.

📍 The greater the number of pins set for the first flush, the higher the yield.

However, with more pinheads competing for the same nutrient base, the smaller are the mushrooms arising from it. Fewer pinheads result in larger mushrooms, but lower total yields.

📍 The substrate will only support the development of a certain number of primordia per flush.

Under normal circumstances with an even pin-set, pinheads may "abort" because of insufficient nutrients or late formation.

📍 Pins that form early delay the growth of neighboring primordia.

This can often be seen along the boundaries of the substrate container where primordia form or along the edges of the cake. At the same time, the rest of the mushroom cake remains completely bald. Sometimes these single primordia are removed to allow for even pin formation over the entire surface of the cake and to obtain a greater yield.

After pinning and primordia formation pay attention to changing fruiting parameters for mushrooms development.

Fruiting parameters for primordia and mushrooms development

When primordia 3-5 mm in size are formed on the mushroom cake (usually this happens after 10-14 days), then the fruiting parameters should be slightly adjusted.

These conditions should be maintained until the immediate harvest.

❇️ Air temperature in growbox remains stable within the range of +21°..+23°C or 70-74°F.

❇️ Relative humidity is reduced to 85-92%, so that we increase the evaporation rate. This is an important requirement for primordia development.

If the humidity remains too high pins development will be suspended. The easiest way to reduce humidity is air temperature increasing literally 1°C or increase FAE.

If RH in the growbox is too low, then spray the walls of the grow box from time to time.

❇️ FAE at least 4 times a day. Under no circumstances should air stagnation be allowed. High humidity and lack of air movement are an excellent breeding ground for pathogenic microorganisms and infection of mushroom cakes. Ideally - the operation of the aquarium compressor on a PERMANENT basis.

❇️ CO2 level no more than 1000 ppm. At the stage of growth of fruiting bodies, fungi emit more carbon dioxide, but a slight increase in the level of CO2 in the grow box is less critical than at the stage of primordia fixation.

❇️ 12 hour on/off light cycle. Diffuse natural light or exposure to a blue-spectrum LED lamp (~435 - 480 nanometers).

🔴 The top layer of mushroom cake should be moist enough. At the same time avoid puddles!

Mushrooms development in dynamics

I'd like to share some examples. Here is Golden Teacher in all its glory. This handsome shroom guy appeared the very first.

Psilocybe cubensis Golden Teacher strain (29th day after inoculation, 11th day in growbox)
Psilocybe cubensis Golden Teacher

26th day after inoculation, 7th day in the growbox:

First psilocybin mushrooms appearance. Thai strain with using cold-shock
Psilocybe Cubensis Thai. 26 days after inoculation, 7 days in growbox
First magic psilocybin fungi Psilocybe Cubensis on the cake
Magic mushroom cakes Psilocybe Cubensis. 26 days after inoculation, 7 days in growbox

Here is 28 days after inoculation and 9th day of fruiting period. Psilocybe Cubensis Thai after cold shocking. Details in the section All you need to know about cold shock for magic mushrooms

Psilocybin mushrooms (Thai strain). Growing after cold shock. 28 days after inoculation
Growing after cold shock (Thai strain). 28 days after inoculation
Psilocybe cubensis Thai strain (28th day after inoculation, 11th day in growbox)
Psilocybe cubensis Thai strain (28th day after inoculation, 11th day in growbox)

Mushroom memes with our funny fungi guy

Funny psilocybin mushroom
Mushroom meme
Meme with magic mushroom
Funny psilocybin mushroom meme

29th day after inoculation and 10th day of fruiting period:

Psilocybe Cubensis Thai strain. 29 days after inoculation and 10 days in growbox
Psilocybe Cubensis Thai strain. 29 days after inoculation and 10 days in growbox
Psilocybe Cubensis (Thai strain). Growth after cold shock
Psilocybe Cubensis (Thai strain). Growth after cold shock
Psilocybe Cubensis Golden Teacher and Thai. 29 days after inoculation
Psilocybe Cubensis Golden Teacher and Thai. 29 days after inoculation and 10 days in growbox

30th day after inoculation and 7th day of fruiting period:

Psilocybe Cubensis Brazil. 30 days after inoculation and 8 days in growbox
Psilocybe Cubensis Brazil (cake 1). 30 days after inoculation, 8 days in growbox
Psilocybe Cubensis Brazil (cake 2). 30 days after inoculation and 8 days in growbox
Psilocybe Cubensis Brazil (cake 2). 30 days after inoculation and 8 days in growbox
Psilocybe Cubensis Thai. 30 days after inoculation and 11 days in growbox
Psilocybe Cubensis Thai. 30 days after inoculation and 11 days in growbox

Growing problems during mushroom fruiting period

During fruiting period you can face with many problems. Most common are:

  • Wrong fruiting parameters (problems with pin setting and primordia development, overlay, mushroom aborts, metabolites, abnormal development and inappropriate appearance of the fungus)
  • Substrate contamination with pathogenic microorganisms (molds, bacteria, viruses, parasites)
  • Genetic problems (mutation, strain degeneration, stroma)
🆘 Why mycelium and mushrooms turned blue and have bruises

It is often newbie cultivators confuse mycelium oxidation and mushroom bruises with contamination. Bruises is a reaction between oxygen and psilocin in mushrooms and mycelium.

Blue color can occur due to any damages or if you touch shrooms or mycelium.

Bruises on mycelium can appear due to lack of moisture in the substrate or casing layer. As a result mycelium torn and become blue.

It's normal reaction when you crop mushrooms.

Bruises are not contaminants and nothing to worry about.

Check out examples in short video:

🆘 Mycelium is cottony, fluffy or crust-like

Stroma and Overlay is a dense cottony mycelium forms on the surface of the casing layer. Some time later it can turn into a crust. Such mycelium doesn't allow moisture and air to pass through and prevents pins and primordia formation.

More examples, main causes of stroma overlay and how to fix it in the section Overlay and Stroma in Mushroom Cultivation

Stroma overlay
Stroma overlay
🆘 Mushroom caps turned black

Fungal abortions are primordia or young mushrooms that have stopped their development. A distinctive feature of abortion is the blackening of mushroom caps. Details in the Mushroom aborts section.

Video demonstration of examples of abortion mushrooms and the reasons for their occurrence:

🆘 Yellow liquid on mushroom mycelium

Transparent yellow-orange-brown liquid without mucus and odor - these are secondary metabolites or waste products of the mycelium. Often formed due to various stresses: temperature changes, drafts, direct sunlight. The metabolites can be caused by minor contamination and the fight of the mycelium's immune system against competitors. Details in the Mycelium metabolites or mushroom pee section

Metabolites are often confused with contamination called Mycogone (aka Wet Bubble).

Video demonstration with examples of metabolites and their causes.

🆘 Mycelium become yellow, beige or brown

Slight pigmentation (beige, yellow, brown mycelium) is a normal reaction due to release of mycelium waste products. Nothing to worry about. It's not contamination. However, it is important to differ it from yellow mold.

🆘 Dark spots on mushrooms and mycelium

The video shows the most beautiful spots on mushrooms and mycelium - spores!


And 1000 more questions you can face with.

Stay tuned!


For successful pins setting, primordia formation and mushrooms development you should maintain necessary microclimate in the growbox. Dispose mushroom cakes with contamination in time. Be patient and attentive.

Enjoy how mushrooms grow. Now they grow very fast from this step.

After primordia formation mushrooms are ready for harvesting in 5-10 days.

The exciting harvesting moment are coming... But before we recommend to prepare your own spore prints for new mycological experiments — Step 11. Day 32-33. How to make spore print 🔽

  1. Cultivation Guide
  2. Pinhead initiation. Fruiting conditions