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Spawning Button Mushroom compost

Join released compost and traceable spawn through a clean, uniform inoculation process.

Practical explanation + detailed referenceSources & review ↓
Close-up of white Agaricus mycelium running through dark compost with small button pinheads, Pradejón, La Rioja, Spain.
Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.Pradejoniensis · CC BY-SA 3.0View 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.

Spawning is the day spawn is mixed into cooled, finished compost and the compost is filled into bags or beds. It takes hours, and it decides whether the crop starts clean and even. This page covers what spawn is and how to check a lot, the figures for the day, the order of work, how contamination gets in, and the decisions to make before the room is closed.

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

Part 01

Spawn is living mycelium of one strain, so check each lot

ICAR-DMR's manual defines spawn simply as grains covered with mushroom mycelium, grown in a laboratory from a pure culture of one strain. Cereal grains such as wheat suit button spawn. The strain does not change on your farm, so the strain you buy is the strain you crop.

Check each lot before spawning day. The manual asks for every bag to show the lot number, date of inoculation, variety or strain and quantity. Agaricus spawn should not be older than 60 days. It is stored cold: the manual gives 4 °C for a cold room, 2 to 4 °C for bags packed in ventilated cartons, and 4 to 6 °C in its spawn standards. It should travel in a refrigerated van, or at night when the air stays below 32 °C, away from heat and dust.

Look at the grain too. The ICAR-DMR button folder wants spawn white, with silky mycelium. The manual lists thin growth that hardly enters the grains, growth that stops short of the bottom of the bag, and patchy growth among faults in spawn making. Freshly made spawn is preferred because its mycelium is still actively growing.

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

A hand holds a polythene bag of fully colonised Volvariella volvacea (paddy straw mushroom) spawn, Vietnam.
A hand holding a polythene bag of fully colonised paddy straw mushroom spawn in Vietnam. Button spawn is a different species, but it too comes in bags, and each bag should show its lot, date and strain. Photo: Zenyrgarden, CC BY-SA 4.0. Source
Part 02

The figures for spawning day

Two ICAR-DMR documents give slightly different spawn rates and fill sizes. Both are shown. Choose one, and write down which you follow.

Compost temperature at spawning25 °CThe compost chapter cools Phase II compost to 25 to 30 °C before spawning.
Ammonia at spawningnot more than 8 to 10 ppmPhase II compost is released below 10 ppm.
Spawn rate, manual0.5 to 0.7 % of wet compost weight
Spawn rate, button folder0.5 to 0.75 % of prepared compostThe folder works this out as 500 to 750 g for 100 kg of compost.
Fill depth, manual12 to 15 / 6 to 8 inches (bags / beds)
Fill per bag, button folder10 to 12 kgNo deeper than one foot in the bag; shelf beds about 6 inches deep.

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

Part 03

Run spawning day in this order

Spawning goes best as one continuous job. Have compost, spawn, room and people ready before the first bag is opened.

  1. Prepare the room two days aheadThe button folder cleans the floor, walls and roof of the spawn-run room two days before filling, then shuts doors and windows. It uses a chemical wash for this; check current label approval before using any chemical.
  2. Clear the compostConfirm it has cooled to about 25 °C and that ammonia is within the limit. If either check fails, hold the batch.
  3. Clean the area and yourselvesWork on a cleaned floor with clean tools and washed hands, doors and windows shut. Where possible, spawn under positive pressure, with filters on the air inlets and air curtains at the doors.
  4. Weigh, then mix evenlyWeigh the spawn against the wet weight of the compost at 0.5 to 0.7 percent, and mix until the grains are spread through the whole mass.
  5. Fill, level and close looselyFill bags 12 to 15 inches deep or beds 6 to 8 inches, press lightly and level the top. Close bag mouths loosely; cover trays or shelves with clean newspaper or a plastic sheet.
  6. Move and recordCarry the filled bags to the spawn-run room and note the date, compost batch, spawn lot and strain for each room.

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

Part 04

Why the spawning hours carry the highest risk

Pasteurised compost is clean, not sterile. For a few hours on spawning day it is cool, moist, open and full of food, and any spore that lands on it has a head start.

The ICAR-DMR manual shows how competitors get in. Spores of Sepedonium, the yellow tikki mould, can reach compost on air currents before or during filling and during spawning. They also come from unpasteurised or spent compost left in a cropping room, or stuck to the bamboo of seasonal racks. That is why the manual asks for high-efficiency air filters during spawning and spawn run, doors and windows kept shut, and clean hands and tools.

Two causes of green mould also belong to spawning day: compost with a low pH, and immature spawn. Both are checked before you mix, not after.

Treating the spawning area and tools is part of the documented method. Do not improvise with chemicals; check current label approval for use in mushroom units first.

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

Close view of two plastic substrate bags; one is streaked dark green and grey, the other is brown with pale growth.
Two sawdust substrate bags from a farm in the Cameron Highlands, Malaysia; the left one is covered in dark green mould instead of white mycelium. They are not button bags, but they show what a contaminated start can turn into. Photo: Arne Müseler, CC BY-SA 3.0 DE. Source
Part 05

Decisions to make before the room is closed

Most spawning mistakes come from sticking to the planned date. These rules put the compost and the spawn first.

IfThe compost is still warmer than 25 to 30 °C.
ThenWait, and cool it with fresh air. Do not spawn warm compost.
IfAmmonia is still present.
ThenDo not spawn. Phase II compost goes back to conditioning; long-method compost gets further turnings, every 2 to 3 days, until the ammonia is gone.
IfYou plan to add a protein supplement.
ThenThe manual finds it more useful after spawn run, just before casing. Added at spawning it raises compost temperature by 4 to 5 °C and can kill mycelium or bring in moulds.
IfA spawn bag has no lot, date or strain, or is older than 60 days.
ThenSet it aside and ask the supplier for a replacement.
IfGrowth in the spawn is thin, patchy or stops short of the bag bottom.
ThenDo not use that lot. The manual treats these as faults in how the spawn was made.

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

Spawning Button Mushroom compost

Agaricus bisporus

Join released compost and traceable spawn through a clean, uniform inoculation process.

Publication
Public editorial page
External review
Not yet recorded · needed from Button Mushroom technical reviewer
Updated
2026-08-22
Evidence records
2
Close-up of white Agaricus mycelium running through dark compost with small button pinheads, Pradejón, La Rioja, Spain.
Mycelium (spawn run) and pinheads on compost (Spain). Photo: Pradejoniensis, CC BY-SA 3.0. Source

Button mushroom crop cycle

  1. CompostDay 0Pasteurised, ammonia below 10 ppm
  2. Spawn run12-14 daysAir 23 ± 1 °C, RH 95%
  3. CasingDay 153-4 cm layer, pH 7-7.5
  4. Case runAbout a weekMycelium reaches the casing valleys
  5. Pinning3-4 daysAir to 15-17 °C, RH 85%, fresh air in
  6. FlushesFlush by flushAir 15-17 °C, RH 80-85%
Picture → explanation → field task

Keep clean and suspect work separate

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

Generated illustration of raw straw separated from closed cultivation bags on a different bench.
02

Protect prepared material

Raw inputs and protected prepared material are separated. Treatment does not protect a substrate indefinitely. Handling afterwards can introduce contamination.

Try this on your farm

Keep work areas, tools and movement routes separated. Label batches so a later problem can be traced to its preparation history.

Generated illustration of a covered waste tub leaving a separate area away from covered harvest crates.
04

Plan the spent-material route

Used material and saleable harvest follow different handling paths. A disposal route can undo clean-work separation if it crosses incoming materials or harvest handling.

Try this on your farm

Map the exit route and cleaning responsibility. Check the actual workflow during a busy room turnaround, not only on a drawing.

Stage08

Crop-stage dashboard

Spawning

Biological state
Mycelium is introduced into selective compost
Operator objective
Create a clean and uniform inoculated batch
Handoff
Begin spawn run with complete batch identity
ObserveInput conditiondistributionhygiene
Depends onReleased compostspawn qualityroom readiness

Quick orientation

Spawning is a biological handoff. Compost readiness, spawn condition, mixing uniformity, temperature and hygiene should be verified before the room is closed for spawn run.

01

System role

Spawning joins the compost and spawn supply chains and begins in-room crop traceability.

02

What to observe

Build a record before making a change.

  • Compost release identity
  • Spawn lot and condition
  • Distribution
  • Clean handling and room readiness

03

Decision framework

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

  • Accept or hold inputs
  • Set batch and room identity
  • Verify mixing
  • Close the room under a documented procedure

04

Dependencies and handoffs

This topic cannot be interpreted in isolation.

  • Released compost
  • Traceable spawn
  • Clean equipment
  • Prepared room
  • Competent handling

05

Practical layer

Start in the room with compost release identity and spawn lot and condition. Record location, stage and recent events before changing the process.

06

Technical layer

The technical model joins released compost, traceable spawn, clean equipment. 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; Technical Bulletins. 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
  • Compost release identity
  • Spawn lot and condition
  • Distribution
  • Clean handling and room readiness
TechnicalHow the interacting system is interpreted
  • Released compost
  • Traceable spawn
  • Clean equipment
  • Prepared room
  • Competent handling
ResearchWhich evidence records govern this page
  • ICAR-DMR-CULTIVATION-MANUAL
  • ICAR-DMR-TECH-BULLETINS

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.SPAWNING.COMPOST_TEMPERATURE

Compost temperature at spawning

25 to 30 °C

Spawn only once the cooled compost sits at 25 to 30 °C with no free ammonia; spawn rate 0.5 to 0.75 percent of compost weight.

Stage
Spawning
Measured at
Compost mass at representative locations
Crop meaning
Connects biological readiness to inoculation risk.
Applicable conditions
Compost readiness; Room condition; Spawn handling
published sourced
Evidence and review record2 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 · institutional

Technical Bulletins

Official index for crop protection, post-harvest, farm design, spawn and developed technologies.

Accessed
2026-08-22
Publisher
ICAR-Directorate of Mushroom Research
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. Technical Bulletins ↗

    ICAR-Directorate of Mushroom Research

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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