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Pinning and initiation

Coordinate the crop-surface transition through temperature, carbon dioxide, air movement, moisture and evaporation.

Practical explanation + detailed referenceSources & review ↓
A dense flush of white button mushrooms fruiting from a compost bag with casing-soil specks, photographed in Assam, India.
Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.Medhi jyoti · CC BY 4.0View full photograph ↗
On this pageChoose a section, or keep reading below

Read this in the full guide: Run a Button mushroom crop from receipt to room reset →

Understand the topic

What you need to know.

Pinning is the few days after venting when white knots form in the casing and swell into buttons. It sets how many mushrooms the first flush carries and how evenly. This page explains the change in the room that starts it, the timings and targets ICAR-DMR publishes, how to read a pin set, how to water from venting to button size, and the mistakes that spoil pins.

Teaching revised 2026-09-24. Source-linked editorial synthesis; this date does not imply independent technical review.

Part 01

The change in the room that tells mycelium to fruit

Until venting, everything in the room has favoured spreading mycelium. Pinning starts when the grower changes three things together.

In the manual's environment section, cooling brings the air down to 15 to 17 °C over 2 to 3 days. At the same time the fresh air vent opens to 30 percent with 70 percent recirculated, which lowers carbon dioxide to 800 to 1000 ppm, and humidity is taken down from 95 to 85 percent. The manual stresses that the three work in synergy: if any one is outside its range, pinning suffers.

Humidity of 85 percent has a purpose. It lets water evaporate slowly from the bed, which draws nutrients upward through the compost and carries carbon dioxide and heat away from the surface. At 17 °C and 85 percent humidity, the manual measures 31 g of water leaving each square metre of bed every hour.

Seasonal growers give the same signal more simply. The ICAR-DMR button folder brings the room to 16 to 18 °C, keeps humidity near 85 percent, and opens doors and windows for a while every morning and evening.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · ICAR-DMR button folder

Controlled room: how the air moves

Cooled, humid air drops from the overhead duct onto the beds, returns through the room, and 20 to 30 percent fresh air is mixed in. About 15 cm per second over the beds, 4 to 6 air changes an hour. Source: ICAR-DMR manual.

Perforated supply ductAHUcooling coilhumidifierreturnfresh air 20-30%
Supply airReturn airBeds
Part 02

Timings and targets from venting to buttons

Two sections of the ICAR-DMR manual give different times to the first pins, and the button folder gives its own time from pin to picking size. The manual marks these timings as strain dependent.

Venting to first pins3 to 4 days, or within a week3 to 4 days in the manual's agronomy section; within a week in its environment section.
Pin to button size3 to 4 daysThe button folder gives 2 to 4 days.
Carbon dioxide at pinning800 to 1000 ppmAllowed to rise to 1000 to 1500 ppm once pins have grown to buttons.
Relative humidity85 %Down from 95 percent in case run.
Casing moisture at pinningabout 50 plus or minus 2 %
Air changes6 per hourFrom venting to the end of the second flush. The agronomy section says 4 to 6 once pins develop.
Air speed over the beds15 cm per secondCheck it at the middle shelf of the central row, not only in the aisle.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · ICAR-DMR button folder

Part 03

Reading a pin set, and what each pattern points to

Walk the room a day or two after pins appear and look at every level of every rack, not just the beds beside the aisle. These are the patterns ICAR-DMR and the NHB report describe.

  • Pins spread evenly over the casing on every shelf: temperature, fresh air, humidity and casing water all reached the whole bed.
  • Pins with a swollen base and a small cap, like an onion: carbon dioxide was too high at pinning. The manual says the same excess can also seal the casing.
  • Long stems with small caps that open early: carbon dioxide is trapped around the growing crop. The NHB report adds that drumstick-like stems can also point to a virus disease.
  • Masses of pins, or pins forming below the casing surface: the NHB report links this to a sudden fall in temperature, too much aeration, or carbon dioxide lowered earlier than recommended, especially on seasonal farms.
  • Mushrooms in tight bunches: the manual asks for the climate controls during pinhead formation to be put right.
  • Pins late or thin on the middle shelf of the centre row: check air movement there. The manual checks it by watching the smoke of a burning incense stick.
  • First-flush pins that are late, form below the surface and come up already open: among the manual's signs of die back, a virus disease. Ask for a diagnosis.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · NHB DPR model, 2018

Polythene compost bags topped with dark casing soil and emerging button-mushroom pinheads in a dim cropping room, Tamil Nadu (uploader is a TNAU student; Tamil caption 'mushroom cultivation method').
Polythene compost bags topped with dark casing soil, with button mushroom pinheads emerging, in a dim cropping room. Photo: Rahumath nisha, CC BY-SA 4.0. Source
Part 04

Watering from venting to button size

The manual divides this stage into times when the bed should get water and a time when it should not.

  1. Vent on a wet layerThe casing should already be wet enough when fresh air comes in and the room cools. Keep it that way until the pins are the size of a pea.
  2. Keep the spray off breaking pinsAvoid spraying water on the beds while the pins are breaking through.
  3. Water again at pea sizeOnce pins reach pea size, the bed needs extra water so they can grow into buttons. From then on, regular sprays and room humidity keep the casing moist.
  4. Spray gently with clean waterUse water fit for drinking, neutral and free from salts. The NHB report links browning of pins to spraying at high pressure, above 0.4 atm, and to heavily chlorinated water.
  5. Watch the two thermometersIf the bed reads cooler than the air, the room air is too dry and the casing is losing water. Humidify the incoming air.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · NHB DPR model, 2018

From venting to picking size

  1. VentAir to 15 to 17 °C over 2 to 3 days; carbon dioxide to 800 to 1000 ppm.
  2. Pins break3 to 4 days later, or within a week; no spraying on the beds.
  3. Pea sizeExtra water so the pins can swell.
  4. Buttons3 to 4 days after pinning; carbon dioxide may rise to 1000 to 1500 ppm.
Part 05

Mistakes that spoil a pin set

Common mistakeCooling the room but leaving the fresh air closed.

Do this insteadChange temperature, fresh air and humidity together. With carbon dioxide left high, pins come out onion shaped or the casing seals.

Common mistakeKeeping the room warm to hurry the crop along.

Do this insteadHold the fruiting range. The manual warns that long high temperature keeps the mycelium growing as threads, seals the casing and stops pinning.

Common mistakeLetting humidity fall below 85 percent to dry the surface.

Do this insteadBelow 85 percent the bed gives up more water, the casing dries and seals, and pinning is lost.

Common mistakePointing fans straight at the beds.

Do this insteadAim for gentle movement over the crop, about 15 cm per second, enough to carry carbon dioxide out of the canopy.

Source: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption

Go deeper

Technical reference, records and tools.

Detailed crop-stage information, parameters, diagrams and specialist tools are kept together below. This material retains its source conditions and review limits.

Open the complete technical reference

Button Mushroom · cultivation stage

Pinning and initiation

Agaricus bisporus

Coordinate the crop-surface transition through temperature, carbon dioxide, air movement, moisture and evaporation.

Publication
Public editorial page
External review
Not yet recorded · needed from Button Mushroom technical reviewer
Updated
2026-08-22
Evidence records
3
A dense flush of white button mushrooms fruiting from a compost bag with casing-soil specks, photographed in Assam, India.
Button mushroom flush on a compost bag with casing soil. Photo: Medhi jyoti, CC BY 4.0. Source

Room climate by crop stage

Button mushroom, room air temperature. Case run spans 23 ± 1 °C (climate section) and 24 ± 1 °C (casing section). Source: ICAR-DMR manual 2011.

10°C15°C20°C25°C30°CSpawn run22-24°C95% RHCase run22-25°C95% RHPinning15-17°C85% RHCropping15-17°C80-85% RH
Temperature bandRelative humidity
Picture → explanation → field task

A crop-room round

AI-generated educational illustrations. Not actual farm photographs, diagnostic evidence or construction specifications.

Generated illustration of an operator inserting a temperature probe into a compost bed.
01

Measure the bed, not only the air

The probe measures growing material at a specific location. Room air and biologically active compost can have different temperatures. One reading is not a whole-room survey.

Try this on your farm

Use a consistent measurement location and method. Record time, crop stage and bed position with the value.

Generated illustration of gentle water application to a bare casing surface before mushrooms emerge.
02

Assess casing before watering

This scene shows casing without developing fruit bodies. Water needs depend on stage and material condition. The picture does not specify a quantity or a universal watering schedule.

Try this on your farm

Check the approved crop protocol and the actual casing condition before deciding how much to apply. Record the application.

Generated illustration of a grower recording different pin densities along mushroom beds.
03

Compare the pinning pattern

The bed does not develop uniformly at every position. Differences can involve inputs, water or room conditions. A patch is an observation, not a diagnosis.

Try this on your farm

Compare fixed locations over successive rounds. Photograph the same patch and record nearby readings before changing settings.

Generated illustration of an empty growing room with racks, dedicated cleaning tools and a hose.
04

Prepare for the next crop

The crop is removed before the room is prepared for reuse. An empty room provides access to surfaces hidden by a loaded crop. Clean appearance alone does not verify disinfection.

Try this on your farm

Follow the farm's validated cleaning and end-of-crop procedure, document completion and resolve defects before refilling.

Stage12

Crop-stage dashboard

Pinning

Biological state
The crop shifts from vegetative development toward fruit-body initiation
Operator objective
Create a controlled and uniform initiation response
Handoff
Protect developing pins into cropping
ObservePin mapsurface stateclimate distribution
Depends onCase-run readinesswater balanceroom control

Quick orientation

Pinning is an interaction, not a single setpoint event. The crop surface, casing water, compost activity and room distribution determine how a nominal control change reaches different rack zones.

01

System role

Pinning converts case-run readiness into organised fruit-body initiation and sets later crop uniformity.

02

What to observe

Build a record before making a change.

  • Pin distribution and timing
  • Surface condition
  • Compost-air temperature relationship
  • Carbon dioxide and air movement by zone

03

Decision framework

Use the observation to narrow a decision, then verify the response.

  • Transition gradually from crop evidence
  • Map unevenness
  • Coordinate water and evaporation
  • Avoid control changes from one centre-room reading

04

Dependencies and handoffs

This topic cannot be interpreted in isolation.

  • Case-run readiness
  • Casing condition
  • Climate-system distribution
  • Water history
  • Sensor quality

05

Practical layer

Start in the room with pin distribution and timing and surface condition. Record location, stage and recent events before changing the process.

06

Technical layer

The technical model joins case-run readiness, casing condition, climate-system distribution. Any operating value must be attached to a registered parameter, measurement location and applicable condition.

07

Evidence boundary

This page is grounded in: Mushroom Cultivation, Marketing and Consumption; Farm Design for White Button Mushroom Cultivation; Physicochemical characterization of casing materials used in Button Mushroom cultivation. Source provenance does not remove the need to check stage, system, date and local applicability.

Progressive depth

Go deeper without losing the field question.

PracticalWhat to notice in the room
  • Pin distribution and timing
  • Surface condition
  • Compost-air temperature relationship
  • Carbon dioxide and air movement by zone
TechnicalHow the interacting system is interpreted
  • Case-run readiness
  • Casing condition
  • Climate-system distribution
  • Water history
  • Sensor quality
ResearchWhich evidence records govern this page
  • ICAR-DMR-CULTIVATION-MANUAL
  • ICAR-DMR-FARM-DESIGN
  • ICAR-MR-CASING-2025

Technical registry

The numbers for this stage, with their source.

Values are published from ICAR-DMR guidance with the stage and measuring point they apply to. A parameter still marked pending has no published Indian value yet.

BUTTON.CLIMATE.AIR_TEMPERATURE

Room air temperature

14 to 25 °C

Spawn run 22 to 24 °C, case run 23 to 25 °C, fruiting 15 to 17 °C in controlled rooms; the seasonal tables give 14 to 18 °C for fruiting.

Stage
Crop-wide
Measured at
Defined crop-zone position
Crop meaning
The control variable that interacts with compost temperature, evaporation and crop stage.
Applicable conditions
Stage; Strain; Sensor location; Room system
published sourced
BUTTON.CLIMATE.CO2

Carbon dioxide concentration

800 to 15,000 ppm

10,000 to 15,000 ppm during spawn run with no fresh air; 800 to 1,000 ppm for pinning; 1,000 to 1,500 ppm during cropping with 20 to 30 percent fresh air.

Stage
Spawn run through cropping
Measured at
Representative room and rack positions
Crop meaning
A crop-activity and ventilation signal that needs stage context.
Applicable conditions
Stage; Crop load; Fresh-air strategy
published sourced
BUTTON.CLIMATE.AIR_VELOCITY

Crop-zone air velocity

0.15 m/s

ICAR-DMR specifies about 15 cm per second over the beds, with 6 air changes per hour in the first two flushes and 4 later.

Stage
Pinning and cropping
Measured at
Crop level at mapped rack positions
Crop meaning
Local evaporation and distribution over the beds, not ventilation quantity.
Applicable conditions
Rack geometry; Crop density; Instrument
published sourced
BUTTON.CASING.MOISTURE_STATUS

Casing moisture at pinning

48 to 52 % moisture

ICAR-DMR gives 48 to 52 percent casing moisture at pinning; the layer itself is 3 to 4 cm deep.

Stage
Casing and case run
Measured at
Representative depth through the casing layer
Crop meaning
Water availability at the crop surface when pins form.
Applicable conditions
Casing material; Depth; Sampling method
published sourced
Evidence and review record3 mapped sources

Sources support the page architecture and conceptual guidance. Technical values remain governed separately in the Button registry.

Tier A · foundational

Mushroom Cultivation, Marketing and Consumption

Broad cultivation, post-harvest and market context. Values are not promoted without page-level review.

Accessed
2026-08-22
Publisher
ICAR-Directorate of Mushroom Research
Open original source
Tier A · foundational

Farm Design for White Button Mushroom Cultivation

Room planning, workflow, environmental-control architecture and engineering vocabulary.

Accessed
2026-08-22
Publisher
ICAR mushroom research institute
Open original source
Tier C · research

Physicochemical characterization of casing materials used in Button Mushroom cultivation

Casing function and material-characterization context. Trial findings remain bounded to the study design.

Accessed
2026-08-22
Publisher
Mushroom Research, ICAR
Open original source

Read the evidence

Sources & review.

Editorial update: 2026-08-22. Independent technical review is not recorded for this entry.

  1. Mushroom Cultivation, Marketing and Consumption ↗

    ICAR-Directorate of Mushroom Research

  2. Farm Design for White Button Mushroom Cultivation ↗

    ICAR mushroom research institute · Foundational official bulletin. Engineering guidance must still be checked against current codes, equipment and project conditions.

  3. Physicochemical characterization of casing materials used in Button Mushroom cultivation ↗

    Mushroom Research, ICAR · 2025

Reading a source is not the same as applying its instructions to every farm. Confirm species, strain, crop stage, system, region and publication date. Old chemical recommendations are not current-use instructions.

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