MushroomFarming / guide

Biology of Agaricus bisporus

Connect fungal biology, mycelial growth and fruit-body development to cultivation decisions.

Practical explanation + detailed referenceSources & review ↓

Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.I. G. Safonov (IGSafonov) · 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.

The button mushroom, Agaricus bisporus, is a fungus. Its body lives inside the compost as fine white threads, and the mushroom you sell is only its fruit. This page explains what the fungus eats, how its spores work, what it needs at each stage, how strains differ, and how to read its signals on the bed. It is for growers who want the reason behind each farm rule.

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

Part 01

A fungus that feeds on what composting leaves behind

Agaricus bisporus makes no food from sunlight. ICAR-DMR describes it as a saprophytic fungus: it lives on dead plant matter. Its carbon comes from the cellulose, hemicellulose and lignin in straw. It also needs nitrogen, other elements such as phosphorus, sulphur, potassium and iron, and vitamins such as thiamine and biotin.

The living body is the mycelium, a web of fine white threads that spreads through the compost. The mushroom is the fruit body that the mycelium raises when conditions change.

Raw straw does not suit it. During composting, heat-loving microbes turn the added nitrogen into their own protein and build a lignin and humus complex, and the mushroom mycelium later feeds on both. Properly made compost is selective, in the manual's word: A. bisporus mycelium grows on it while competing organisms are practically shut out. That is why a button farm spends so much care on compost.

The fungus even shapes the recipe. Its mycelium produces oxalic acid, and the gypsum added to compost supplies calcium that turns this acid into calcium oxalate.

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

White button mushrooms in the corner of the frame with white thread-like mycelium running through dark growing medium. — Young button mushrooms beside the white mycelium strands that feed them, exposed at the edge of the growing medium. The strands are the fungus; the mushrooms are its fruit. Photo: Ірина Бучнєва, CC BY 4.0. Source

Part 02

The fruit body, and a species whose spores come in twos

The mushroom has a cap, gills under the cap where spores form, a stem, and a veil: a thin skin that covers the gills while the cap is closed. ICAR-DMR harvests while the cap is still hard and the veil is closed, so a farm crop is sold before it sheds spores.

How those spores are made sets this species apart. The manual describes A. bisporus as secondary homothallic with bispored basidia. In plain words, its spores are borne in twos, and most of them are self-fertile, so a single spore can grow into a fertile culture. Its summer relative A. bitorquis and the oyster mushrooms bear spores in fours. Their single spores are self-sterile, and breeders use them to make new strains.

Growers meet this biology through spawn, not spores. Every crop starts from a laboratory culture multiplied on grain. The manual warns that cultures raised from many spores degenerate faster than single-spore cultures. It lists bare patches on the bed, deformed fruit bodies with few or no gills, and weeping mushrooms among the signs of a degenerated culture.

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

A button mushroom and where it lives

What we eat is the fruit. The organism itself lives inside the compost as mycelium.

Part 03

What the fungus needs, in ICAR-DMR's own figures

These are the organism's needs as ICAR-DMR documents state them. The manual marks several as strain dependent. Room settings for each stage are taught on the stage pages.

Temperature for mycelium to spread22 to 25 °CSpecies table in the ICAR-DMR seasonal folder. The manual holds spawn-run air at 23 plus or minus 1 °C.

Temperature for fruiting14 to 18 °CSeasonal folder. The manual's summer button chapter gives 16 plus or minus 2 °C for A. bisporus.

Bed compared with room air1 to 2 °C warmerThe working mycelium and compost make heat, so the bed runs above the air.

Carbon dioxide while spreading10000 to 15000 ppmA high level speeds vegetative growth. For pinning it is brought down to 800 to 1000 ppm.

Water in a mushroomnearly 90 %Mycelium draws water from compost in spawn run, from compost and casing in case run, and from casing while fruiting.

Compost pH for best growth7.2 to 7.8Outside this band the mycelium grows slowly.

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

Part 04

Traits that change with the strain in your spawn

Spawn carries a strain, and the strain carries part of the biology. The manual says yield and quality depend on the genotype, the environment and the way the two interact. ICAR-DMR's manual and the NHB model project report record differences such as these.

Fruiting temperature: the NHB report lists 15 plus or minus 1 °C for DMR-NBS-5 and 18 plus or minus 2 °C for S-11, while every strain it gives temperatures for runs spawn at 24 plus or minus 2 °C.
Veil opening: early in S-11, very late in DMR-button-03 and DMR-NBS-1, according to the same report.
Flush pattern: the manual's strain table describes NCS-100 as peaking in the first flush and NCS-101 in the second.
Shape: S-11 and P-1 are described as long stemmed with caps that open quickly, and S-130 as tough, with a small stem and a broad cap.
Colour: DMR-NBS-1 and DMR-NBS-5 are listed as non-browning strains.
Size against number: the manual notes that when more fruit bodies come in a flush, each one weighs less.
Species, not only strain: A. bitorquis, the summer white button, needs 4 to 6 °C more warmth than A. bisporus and fruits at about 24 °C.

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

Part 05

Read the fungus before you change the room

The fungus answers every change in the room, and the answer shows on the bed. These links come from the ICAR-DMR manual. Check the reading before you act on it.

IfThe thermometer in the bed reads lower than the one in the air.: ThenHumidity has fallen and the casing is losing water. The manual calls a bed cooler than the air a situation to avoid; normally the bed runs 1 to 2 °C warmer.
IfThe room stays warm after case run and pins do not come.: ThenThe mycelium keeps growing as threads and seals the casing, which then stops taking up water. Bring the air down into the fruiting range.
IfCompost pH was above the 7.2 to 7.8 band at spawning.: ThenExpect slow growth. The manual links high compost pH to white plaster mould.
IfCompost pH was below that band, or the spawn was immature.: ThenThe manual links low pH and immature spawn to green mould. Record both so the next batch can be corrected.
IfBare patches, fruit bodies with few or no gills, or weeping mushrooms appear.: ThenThese are among the manual's signs of a degenerated culture. Record the spawn lot and strain and report them to the spawn supplier.

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 · concept guide

Biology of Agaricus bisporus

Agaricus bisporus

Connect fungal biology, mycelial growth and fruit-body development to cultivation decisions.

Publication: Public editorial page
External review: Not yet recorded · needed from Button Mushroom technical reviewer
Updated: 2026-08-22
Evidence records: 3

A woman picker with a woven basket harvests button mushrooms by hand from tiered bamboo bed racks, PT Dieng Djaya farm, Wonosobo, Central Java (archival, 1979). Downloaded as the 3840px Commons JPEG render; original is 4972x3177 image/tiff (94 MB). — Woman hand-harvesting button mushrooms from tiered bamboo bed racks into a basket (Indonesia). Photo: Steijlen, Fridus, CC BY 4.0. Source

A button mushroom and where it lives

What we eat is the fruit. The organism itself lives inside the compost as mycelium.

Quick orientation

The crop is not a passive object in a controlled room. It grows through a selective compost, interacts with casing and changes its respiration, heat and water relationships through the cycle.

System role

Biology provides the reason behind compost selectivity, spawn run, casing, initiation and flush behaviour.

What to observe

Build a record before making a change.

Colonisation pattern rather than colour alone
Heat and gas production as crop activity changes
The boundary between compost, casing and air
Morphology by stage and location

Decision framework

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

Interpret a measurement through biological stage
Avoid diagnosing health from one visual sign
Separate organism response from equipment response
Preserve strain and batch traceability

Dependencies and handoffs

This topic cannot be interpreted in isolation.

Compost ecology
Mycelial condition
Casing microenvironment
Water and evaporation
Room distribution

Practical layer

Start in the room with colonisation pattern rather than colour alone and heat and gas production as crop activity changes. Record location, stage and recent events before changing the process.

Technical layer

The technical model joins compost ecology, mycelial condition, casing microenvironment. 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; Research programmes; ICAR-DMR Annual Report 2024. 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 rather than colour alone
Heat and gas production as crop activity changes
The boundary between compost, casing and air
Morphology by stage and location

TechnicalHow the interacting system is interpreted

Compost ecology
Mycelial condition
Casing microenvironment
Water and evaporation
Room distribution

ResearchWhich evidence records govern this page

ICAR-DMR-CULTIVATION-MANUAL
ICAR-DMR-RESEARCH
ICAR-DMR-ANNUAL-2024

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 · institutional

Research programmes

Research themes across production, protection, improvement and post-harvest.

Accessed: 2026-08-22
Publisher: ICAR-Directorate of Mushroom Research

Open original source

Tier A · institutional

ICAR-DMR Annual Report 2024

Recent institutional research, programme and technology context.

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.

Mushroom Cultivation, Marketing and Consumption ↗
ICAR-Directorate of Mushroom Research
Research programmes ↗
ICAR-Directorate of Mushroom Research
ICAR-DMR Annual Report 2024 ↗
ICAR-Directorate of Mushroom Research · 2024

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.

See something that needs correcting? Tell us →