MushroomFarming / guide

Spawn run

Manage colonisation by reading compost activity, room load, distribution and contamination risk together.

Practical explanation + detailed referenceSources & review ↓

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 ↗

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Understand the topic

What you need to know.

Spawn run is the stretch of about two weeks after spawning when mycelium grows out from every spawn grain and fills the compost. Little shows from outside, so the grower manages it by thermometer and by eye. This page explains what the mycelium is doing, the settings ICAR-DMR uses, the signs worth recording, the daily routine, and what to do when the run is warm, slow or uneven.

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

Part 01

What the mycelium does between spawning and casing

Each spawn grain is a starting point. Threads grow out of it in every direction, feed on the compost and meet the threads from neighbouring grains until the whole mass is one web.

Growth makes heat and carbon dioxide. ICAR-DMR's manual expects the bed to run 1 to 2 °C warmer than the room air. It keeps the fresh air shut so that carbon dioxide builds up, because a high level speeds this vegetative growth. Temperature also moves humidity: as the room warms, relative humidity falls.

The run ends when the compost has changed colour all the way through. The manual describes dark brown compost turning light brown. The ICAR-DMR button folder describes it turning white, like mould, as the threads fill it. Both mark the point at which mycelium has filled the compost.

Under controlled conditions this takes 12 to 14 days. The button folder gives 12 to 15 days for seasonal rooms. Casing follows once the run is complete, not on a fixed date.

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

From spawn grain to colonised compost

GrainEach spawn grain is a starting point for threads.
SpreadThreads grow out in every direction, giving off heat and carbon dioxide.
JoinThreads from neighbouring grains meet until the compost is one web.
Colour changeDark brown compost turns light brown, or mould-white in the folder's words, over 12 to 14 days.
CaseCasing goes on once the change runs right through.

Part 02

The room settings ICAR-DMR uses for spawn run

These are the manual's settings for a controlled room, with the button folder's seasonal figures in the notes. The manual marks carbon dioxide as strain dependent.

Air temperature23 plus or minus 1 °CThe button folder gives 22 to 25 °C for seasonal rooms.

Bed temperature24 to 25 °C1 to 2 °C above the air.

Relative humidity95 %The button folder gives 80 to 90 percent for seasonal rooms.

Carbon dioxide10000 to 15000 ppmGiven in the manual's spawning steps as 1.0 to 1.5 percent.

Fresh airnone all air recirculatedThe fresh air valve stays closed through the run.

Upper limit26 to 27 °CTemperatures above this during spawn run and after casing should be avoided.

Duration12 to 14 daysThe button folder gives 12 to 15 days.

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

Part 03

Signs to record on your marked bags

Check the same marked bags each day, without opening them more than you must. These are signs the ICAR-DMR manual and the NHB model report describe. A sign is a reason to ask for an assessment, not a diagnosis.

Normal progress: white threads spreading evenly from the grains, with no coloured patches.
Olive green mould: a fine greyish-white growth in the compost or on its surface about 7 to 10 days after spawning, with the spawn growing slowly; later, small grey-green burr-like bodies on the straw.
Brown plaster mould: whitish growth on exposed compost or on bag sides where moisture condenses, thickening into patches that turn tan, brown and then rust. Mushroom mycelium does not grow where it sits.
False truffle: small wefts of white to cream mycelium in the compost, later wrinkled lumps like small brains, 0.5 to 3 cm across, while the compost turns dull brown.
Sepedonium or tikki mould: white growth turning yellow or tan, usually in the lower layers or at the bottom of the bag.
Ink caps: slender, bell-shaped mushrooms rising from the compost, cream at first and later bluish black. They point to ammonia left in the compost.
Stroma: dense white patches of mushroom mycelium that peel off the surface. The NHB report links them to the spawn or its handling, and to high carbon dioxide with wet compost and a long run.

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

Part 04

Hold the run steady, day by day

A spawn run goes well when nothing changes suddenly. This routine follows the manual for controlled rooms and the button folder for seasonal ones.

Keep the room closedIn a controlled room all air is recirculated and the fresh air valve stays shut. In a seasonal room, keep doors and windows closed except when you must go in.
Read two thermometersPlace one stem thermometer in the compost and one in the air a few centimetres away. Record both at the same times each day.
Remove heat before it buildsIf the bed climbs, increase cooling. In the manual's rooms the heat leaves through the cooling coils of the air handling unit.
Hold the humidityControlled rooms run at 95 percent. The button folder raises humidity in seasonal rooms by spraying the walls and filling the floor with water, and sprays the newspaper over shelf beds once or twice a day.
Leave the bags shutOpening bags to look lets in flies and spores. Judge progress from the marked bags and their visible sides.
Finish on the colourCase when the compost has changed colour right through. Growers cropping round the year ruffle the compost at this point, just before casing.

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

A spawn-run check, each morning

ReadBed and air thermometers, at the same hour every day.
CompareThe bed should sit 1 to 2 °C above the air.
ActCool the room if the bed is heading for 26 to 27 °C.
Look and recordMarked bags from outside; write readings, signs and bag positions.

Part 05

When the run is warm, slow or uneven

Most spawn-run problems can still be corrected at this stage, once the cause is found. These rules follow the manual and the NHB report.

IfThe bed temperature climbs towards 26 to 27 °C.: ThenCool the room now. The manual says to avoid this range during spawn run, and high temperature favours both false truffle and brown plaster mould.
IfThe compost is still dark after 14 days.: ThenDo not case yet. Check the temperature record, the compost batch and the spawn lot, and ask for an assessment before deciding.
IfSome bags run well and others lag.: ThenCompare their positions and material lots before changing anything, because the room, the compost and the spawn can each cause lagging bags.
IfYou want to add a protein supplement.: ThenNow is the manual's preferred time: after the run and before casing. Expect the compost to warm by 4 to 5 °C, and use it only on good compost.
IfA bag shows a coloured patch.: ThenKeep it closed, move it away from clean bags, and record where it stood and which lot it came from.

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

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

Spawn run

Agaricus bisporus

Manage colonisation by reading compost activity, room load, distribution and contamination risk together.

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

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

Stage09

Crop-stage dashboard

Spawn run

Biological state: Mycelium colonises the compost and generates metabolic heat
Operator objective: Support uniform colonisation without avoidable stress
Handoff: Apply casing only after readiness review

ObserveColonisationcompost heatdistribution

Depends onSpawningroom capacityhygiene

Quick orientation

During spawn run, the crop is biologically active inside compost. Compost temperature may diverge from room air, so equipment state and one air reading cannot describe the full bed.

System role

Spawn run converts a mixed inoculation into colonised compost ready to interact with casing.

What to observe

Build a record before making a change.

Colonisation pattern
Compost heat by zone
Room-air and compost relationship
Abnormal patches or odour

Decision framework

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

Adjust room operation from mapped evidence
Avoid unnecessary disturbance
Investigate uneven zones
Confirm readiness for casing

Dependencies and handoffs

This topic cannot be interpreted in isolation.

Spawning uniformity
Compost quality
Heat-removal capacity
Sensor placement
Room hygiene

Practical layer

Start in the room with colonisation pattern and compost heat by zone. Record location, stage and recent events before changing the process.

Technical layer

The technical model joins spawning uniformity, compost quality, heat-removal capacity. Any operating value must be attached to a registered parameter, measurement location and applicable condition.

Evidence boundary

This page is grounded in: Mushroom Cultivation, Marketing and Consumption; Farm Design for White 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

Colonisation pattern
Compost heat by zone
Room-air and compost relationship
Abnormal patches or odour

TechnicalHow the interacting system is interpreted

Spawning uniformity
Compost quality
Heat-removal capacity
Sensor placement
Room hygiene

ResearchWhich evidence records govern this page

ICAR-DMR-CULTIVATION-MANUAL
ICAR-DMR-FARM-DESIGN

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.SPAWN_RUN.COMPOST_TEMPERATURE

Compost temperature during spawn run

22 to 25 °C

Hold the compost at 22 to 25 °C (room air 22 to 24 °C) in the dark for 12 to 15 days at about 95 percent humidity.

Stage: Spawn run
Measured at: Within compost at representative bed positions
Crop meaning: Metabolic heat, room load and colonisation speed.
Applicable conditions: Crop age; Bed depth; Room loading

published sourced

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

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 · 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

Read the evidence

Sources & review.

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

Mushroom Cultivation, Marketing and Consumption ↗
ICAR-Directorate of Mushroom Research
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.

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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