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Spawning oyster substrate

Join a cooled, treated substrate batch to traceable spawn through a clean method. Evidence, method and India-context boundaries remain visible.

Practical explanation + detailed referenceSources & review ↓

Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.Soumendra Kumar Sahoo · CC BY-SA 4.0View full photograph ↗

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Understand the topic

What you need to know.

Spawning mixes grain spawn into treated, cooled straw and packs the mix into bags. This page covers what fresh oyster spawn is, how much to use, how to mix it, and how to fill, close and perforate each bag, with the ICAR-DMR manual and oyster folder figures side by side. What happens inside the bag afterwards is on the spawn run page.

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

Part 01

Spawn is grain carrying a pure culture, and it ages quickly

Spawn is the seed of the crop: sterilised grain that a pure culture of Pleurotus has grown through. The ICAR-DMR manual says oyster mycelium covers wheat grain in 10 to 15 days, and reports jowar and bajra grain as superior to wheat.

Oyster spawn does not keep for long. It grows so fast that spawn 25 to 30 days old starts forming mushrooms inside the bottle. The manual calls freshly prepared grain spawn, 20 to 30 days old, the best for spawning. The oyster folder says it should be no more than 30 days old. The manual's spawn standard allows up to 30 to 45 days for Pleurotus, stored at 4 to 6 °C. Follow the tightest limit that applies to your lot, along with the supplier's own label.

The oyster folder also says to buy spawn before you start preparing the straw. Some growers spawn new bags with mycelium taken from a running bag. The manual allows this on a small scale only, because contamination in infested straw travels with it.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

From pure culture to a spawned bag

Pure cultureA true-to-type Pleurotus culture, which the manual's spawn standard says must come from an authentic source.
Grain spawnThe culture grown on sterilised grain; oyster covers it in 10 to 15 days.
Fresh spawnUsed at 20 to 30 days old, before it starts fruiting in the bottle.
Spawned bagMixed into treated, cooled straw at 2 to 3 percent of its wet weight.

Part 02

How much spawn to use

The manual and the oyster folder state the rate in different ways, but they land in the same range. The percentage is worked on wet straw; the folder's quintal figure is worked on dry straw.

Spawn rate, manual2 to 3 % of wet substrate weight

One bottle, manual300 gEnough for 10 to 12 kg of wet substrate, or 2.8 to 3 kg of dry substrate.

Per bag, oyster folderabout 100 g per 4 kg of wet straw100 g in 4 kg works out to 2.5 percent of wet weight. That percentage is our arithmetic; the folder does not print it.

Per quintal, oyster folder10 kg of spawn per quintal of dry straw

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

Part 03

Mix, fill, close and perforate each bag

Spawn in a room that was cleaned and disinfected two days before and kept closed since. The oyster folder uses formalin for this; doses are not given here, so check current label approval first.

Check the strawIt should be treated, drained, cooled to room temperature and pass the squeeze test.
WeighWeigh the wet straw for each bag and the spawn that goes with it at your chosen rate.
MixMix the spawn right through the straw, or add it in layers as you fill; the manual allows either way.
FillPack the mix into polythene bags. The folder uses bags of 40 to 45 cm by 30 to 35 cm; the manual uses 60 by 45 cm bags of 125 to 150 gauge.
CloseFold the mouth of the bag shut, or cover the straw with newspaper to hold in its moisture, as the oyster folder describes.
PerforatePunch holes on all sides and in the bottom: about 10 to 12 holes of 5 mm in the folder, or 10 to 15 holes of 0.5 to 1 cm in the manual.
LabelWrite the spawning date and the spawn lot on each bag so any problem can be traced back.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

Part 04

Why the bag is perforated, and when a box works instead

A closed polythene bag keeps the straw moist, but a bag without holes traps two things: excess water and carbon dioxide. The manual places the holes on all sides and especially in the bottom so excess water can leach out. It also reports that perforated bags crop earlier, by 4 to 6 days, than unperforated ones, because carbon dioxide builds up in a closed bag and holds back fruiting. The oyster folder gives a third reason: the holes stop the bag temperature rising above 30 °C.

A bag is not the only container. The manual also packs spawned substrate into blocks. A polythene sheet of 200 to 300 gauge is spread in a rectangular wooden or metal box, filled with spawned substrate, folded in from all four sides, pressed tight and tied with nylon rope. The block is incubated as it is, and the sheet is removed once the mycelium has grown through. The manual also mentions empty fruit packing cartons and wooden boxes as containers.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

Making a block instead of a bag, as the manual describes

Line the boxSpread a polythene sheet of 200 to 300 gauge in a rectangular wooden or metal box.
FillFill the lined box with spawned substrate.
Fold and tieFold the sheet in from all four sides, press the block tight and tie it with nylon rope.
Incubate, then unwrapIncubate the block as it is and remove the sheet once the mycelium has grown through.

Part 05

Spawning mistakes and what to do instead

Common mistakeOrdering spawn after the straw is already treated.

Do this insteadOrder first. The oyster folder says spawn should be bought before straw preparation begins.

Common mistakeUsing a bottle in which mushrooms have started to form.

Do this insteadPlan orders around your spawning date. The manual notes oyster spawn begins fruiting in the bottle at 25 to 30 days old.

Common mistakeSpawning new bags from a running bag at commercial scale.

Do this insteadUse grain spawn from a known lot. Spawning from active mycelium can carry contamination from one bag to the next.

Common mistakeSpawning in a room that has not been cleaned.

Do this insteadClean and disinfect the spawning room two days ahead and keep it shut until you spawn.

Common mistakeApplying the 2 to 3 percent rate to dry straw.

Do this insteadThat rate is on wet weight. On dry straw the oyster folder's figure is 10 kg of spawn per quintal.

Common mistakeSealing a bag with no holes.

Do this insteadPerforate every closed bag so excess water leaches out and heat and carbon dioxide do not build up.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

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

oyster · cultivation stage

Spawning oyster substrate

Join a cooled, treated substrate batch to traceable spawn through a clean method. Evidence, method and India-context boundaries remain visible.

Publication: Editorial review in progress
Evidence records: 5
External review: Not yet recorded
Wild ID: Not provided

Chopped yellow straw partly covered and bound by dense white mycelium. — White mycelium of golden oyster mushroom binding chopped straw together during spawn run. Photo: Rob Hille, CC BY-SA 3.0. Source

The oyster bag method in six steps

Source: ICAR-DMR oyster folder and the 2011 manual.

Chop the strawWheat or paddy straw cut to 2 to 3 cm (manual method uses 5 to 10 cm).Day 0
Hot-water treatmentFolder: 60 to 65 °C for 20 to 30 minutes (manual: 65 to 70 °C for one hour), then drain off the excess water.Day 0
Spawn and fill bags2 to 3 percent spawn on wet-straw weight, in layers; 10 to 12 holes per bag (manual: 10 to 15).Day 0
Spawn run22 to 26 °C in the dark for 15 to 25 days until the bag is white through.Days 1 to 25
Open the bag and fruitLight, fresh air, 75 to 85 percent humidity, CO₂ below 600 ppm (folder: 800 ppm). Pins in about a week.From day 16
Harvest and next flushNext flush 8 to 10 days later. Manual: 500 to 700 kg from one tonne of dry straw in 45 to 60 days.Up to day 60

Quick orientation

Join a cooled, treated substrate batch to traceable spawn through a clean method. This topic belongs to a Pleurotus substrate-bag or validated block system. The species or strain, substrate treatment and fruiting-air context must travel together.

Why this stage matters

Join a cooled, treated substrate batch to traceable spawn through a clean method.

Method boundary

This topic belongs to a Pleurotus substrate-bag or validated block system. The species or strain, substrate treatment and fruiting-air context must travel together.

Confirm the culture as Pleurotus spp., with strain or variety recorded where available.
Confirm one method: straw bag or validated lignocellulosic bag or block.
Record substrate source, treatment class, batch and contamination observations.

Observe and record

Use batch records, stage dates, room observations and contamination patterns. Compare the crop with its own prior condition before changing several variables at once.

Evidence status

The page publishes process relationships supported by primary institutional sources. Numeric recipes remain absent where source context, strain identity or specialist review is incomplete.

Production method records

One species can require more than one cultivation model.

OYS-STRAW-BAG

Treated straw bag system

Substrate: clean cereal straw with method evidence
Container: perforated or opened cultivation bag
Treatment: Pasteurization-class treatment or another validated method; not interchangeable with sterilization.
Scale context: home trial to commercial batch, with different hygiene and climate responsibilities

Material check
Treatment
Cooling and moisture check
Spawning
Spawn run
Fruiting transition
Cluster harvest

Trace the boundary

Evidence and limitations

institutional · tier AResearch programmes

Current institutional scope for cultivated and specialty mushroom research in India.

Research scope does not by itself establish a farm recommendation, commercial readiness or strain-specific operating range.

Open primary source

technical-bulletin · tier ATechnologies developed by ICAR-DMR

Institutional method history for oyster, milky, paddy straw, shiitake and selected specialty mushrooms.

Method descriptions are context-specific and contain numeric and broad substrate statements that require independent technical review before operational publication.

Open primary source

current-advisory · tier ACurrent crop advisory

Time-stamped Indian seasonal crop context and the need to choose oyster species for conditions.

Chemical directions are excluded from this platform unless a current label and jurisdiction are independently verified.

Open primary source

technical-bulletin · tier AOyster mushroom cultivation FAQ

Indian institutional distinction between warm- and cool-fruiting Pleurotus species, plus an occupational spore-exposure warning.

The species bands are source context, not a strain guarantee. Generic yield, storage and legacy chemical statements are not carried into operational guidance.

Open primary source

technical-bulletin · tier APost-harvest technology of mushrooms

Species-specific post-harvest deterioration patterns and handling context.

Historic shelf-life statements depend on maturity, handling, packaging and storage conditions and are not reproduced as guarantees.

Open primary source

Read the evidence

Sources & review.

Editorial update: 2026-09-03. Independent technical review is not recorded for this entry.

Research programmes ↗
ICAR Directorate of Mushroom Research
Technologies developed by ICAR-DMR ↗
ICAR Directorate of Mushroom Research · 2020
Current crop advisory ↗
ICAR Directorate of Mushroom Research · 2026
Oyster mushroom cultivation FAQ ↗
ICAR Directorate of Mushroom Research
Post-harvest technology of mushrooms ↗
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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