Sterile CVG Mushroom Grow Bag

Sterilised Bulk CVG Substrate FAQ

What is CVG substrate?

CVG is a mushroom-growing substrate made from:

• Coco coir

• Vermiculite

• Gypsum

Coco coir forms the main body of the substrate and retains moisture.

Vermiculite improves water retention and creates air spaces throughout the mixture.

Gypsum provides calcium and sulphur while helping maintain a loose, workable substrate structure.

Our CVG is professionally hydrated, pressure sterilised and sealed, removing the need to prepare and sterilise the mixture yourself.

What is included in each bag?

Each bag contains approximately 2 kg of prepared CVG substrate.

The mixture includes:

• Hydrated coco coir

• Vermiculite

• Gypsum

The substrate is supplied without grain spawn, liquid culture or mushroom mycelium.

A suitable mushroom culture and fully colonised grain spawn must be obtained separately.

Is the CVG ready to use?

Yes. The CVG arrives:

• Properly mixed

• Hydrated

• Pressure sterilised

• Sealed

• Ready to combine with colonised grain spawn

You do not need to add water, vermiculite or gypsum before use.

Open the bag only when your grain spawn is fully colonised and you are ready to prepare the growing container.

Is the CVG sterilised or pasteurised?

Our CVG is pressure sterilised.

Sterilisation significantly reduces the microorganisms present in the substrate, providing a clean starting environment for mushroom cultivation.

The substrate must still be handled carefully after opening. Exposure to unclean hands, tools, surfaces or air can introduce mould spores and bacteria.

Sterilised substrate is not permanently protected once the bag has been opened.

Does the CVG contain mushroom culture?

No. The CVG contains prepared substrate only.

It does not contain:

• Mushroom liquid culture

• Mushroom spores

• Grain spawn

• Living mycelium

• A pre-established mushroom culture

You will need to mix the substrate with fully colonised grain spawn before using it as a bulk fruiting substrate.

Browse our selection of mushroom liquid cultures if you need a culture to produce your own grain spawn.

Can I inject liquid culture directly into CVG?

Injecting liquid culture directly into bulk CVG is not the recommended method.

CVG contains very little readily available nutrition compared with sterilised grain. A small amount of liquid culture would also create only a limited number of inoculation points throughout the substrate.

The recommended process is:

1. Use liquid culture to inoculate sterilised grain.

2. Allow the grain to become fully colonised.

3. Break up the colonised grain spawn.

4. Mix the grain spawn evenly throughout the CVG.

5. Allow the mixture to colonise before fruiting conditions are introduced.

Our 2kg Sterilised Wheat Grain Bag can be inoculated directly with a suitable liquid culture.

Why should I use grain spawn with CVG?

Grain spawn provides the established mycelium and much of the nutrition required for colonisation.

Each colonised grain becomes an individual growth point after it is mixed throughout the CVG.

This provides:

• Faster colonisation

• More even mycelial distribution

• Greater nutritional support

• Reduced opportunity for competing organisms

• More consistent use of the bulk substrate

CVG helps maintain moisture, structure and aeration around the colonised grain.

The two materials perform different roles and are normally used together.

Can I use an uncolonised grain bag with CVG?

No. Grain should be fully colonised before it is mixed with CVG.

Uncolonised grain is highly nutritious and vulnerable to contamination. If it is mixed into an open bulk substrate before the mushroom mycelium has established, mould or bacteria may colonise it first.

Fully colonised grain should show healthy species-appropriate mycelium throughout the bag with no large uncolonised sections.

Do not use grain that appears:

• Slimy

• Sour-smelling

• Excessively wet

• Green, black, pink or unusually coloured

• Partially colonised

• Contaminated

Which gourmet mushrooms can be grown using CVG?

CVG can be used experimentally as a bulk substrate or moisture-retaining component for selected saprotrophic mushroom species.

Some Oyster mushroom cultures may colonise a coir-based bulk substrate when it is mixed with a generous amount of healthy grain spawn.

Potential experimental options include:

• Pearl Oyster

• Blue Oyster

• Phoenix Oyster

• Pink Oyster

• Golden Oyster

• King Oyster

• Black Pearl Oyster

• King Blue Oyster

• Tarragon Oyster

However, Oyster mushrooms generally perform more predictably on straw, hardwood sawdust or another lignocellulosic substrate containing more usable plant fibre.

CVG should not automatically be treated as the best substrate for every gourmet mushroom species.

Is CVG suitable for Portobello mushrooms?

CVG can be used as a casing layer for Portobello mushrooms.

Portobello, Agaricus bisporus, should first colonise a properly prepared compost-based substrate.

Once the compost is colonised, a layer of hydrated CVG can be applied over the surface to:

• Retain moisture

• Support pin formation

• Protect the compost surface

• Maintain a humid microclimate

• Provide physical support for developing mushrooms

CVG does not replace the nutrient-rich mushroom compost underneath.

Our Portobello Liquid Culture can be expanded on sterilised grain before the grain spawn is transferred to properly prepared compost.

How thick should a Portobello casing layer be?

A practical starting depth is approximately 3 to 4 cm of loosely applied CVG.

The casing should be:

• Evenly distributed

• Moist but not waterlogged

• Loose enough to maintain air spaces

• Lightly levelled

• Free from heavy compression

Do not mix the casing deeply into the compost.

The casing layer sits above the colonised compost and serves a different purpose from the main nutritional substrate.

Is CVG suitable for Lion’s Mane?

CVG is not the recommended primary substrate for Lion’s Mane.

Lion’s Mane is a hardwood-decaying species and performs more predictably on supplemented hardwood sawdust.

For Lion’s Mane and related Hericium species, use our:

• Sterilised Hardwood and Wheat Bran Substrate

• Sterile Hardwood Mushroom Grow Bag

These products provide the woody material and nutrition preferred by Lion’s Mane mycelium.

Is CVG suitable for Shiitake?

CVG is not the recommended primary substrate for Shiitake.

Shiitake is a hardwood-decaying species that is normally cultivated on supplemented hardwood sawdust or hardwood logs.

A CVG mixture does not provide the same woody nutrition or structure.

Use our Sterilised Hardwood and Wheat Bran Substrate or Sterile Hardwood Mushroom Grow Bag for Shiitake cultivation.

Is CVG suitable for Chestnut, Maitake, Enoki or Reishi?

CVG is not the preferred primary substrate for Chestnut, Maitake, Enoki or Reishi mushrooms.

These species are naturally adapted to woody materials and generally perform better on:

• Hardwood sawdust

• Supplemented hardwood substrate

• Hardwood pellets

• Appropriate logs

• Other species-specific woody media

For these species, our 2kg Sterilised Hardwood and Wheat Bran Substrate is the more appropriate option.

Is CVG suitable for Wine Cap?

CVG should not be used as the main substrate for Wine Cap or Golden Wine Cap.

Wine Cap mushrooms perform best in outdoor beds containing:

• Hardwood chips

• Straw

• Hardwood mulch

• A mixture of chips and straw

• Other suitable plant-based materials

CVG may retain moisture, but it does not provide the same long-term woody nutrition as hardwood chips or straw.

Is CVG suitable for Chanterelles or Hedgehog mushrooms?

No. CVG cannot replace the living host tree required by Chanterelles and Hedgehog mushrooms.

These are mycorrhizal species that must establish a relationship with suitable living tree roots before mushroom production can occur.

CVG can retain moisture, but it cannot provide the biological root association required by these fungi.

Is CVG suitable for Chicken of the Woods?

CVG is not the recommended substrate for Chicken of the Woods.

Chicken of the Woods is a wood-decaying species that requires hardwood-based material such as:

• Hardwood sawdust

• Hardwood chips

• Dense hardwood blocks

• Dead hardwood logs

• Supplemented hardwood substrate

CVG lacks the woody structure and nutrition preferred by this species.

Can I mix CVG with hardwood substrate?

Yes, but the usefulness of the mixture depends on the mushroom species.

Adding a small amount of CVG to a hardwood-based substrate may increase water retention and change its texture.

However, adding too much can dilute the hardwood and reduce the amount of suitable nutrition available to wood-decaying mushrooms.

For hardwood-loving species, the main substrate should remain hardwood-based.

Any experimental mixture containing nutrient supplements should be properly sterilised before inoculation.

Can I mix CVG with straw?

Yes. CVG can be mixed with prepared straw as an experimental moisture-retaining component.

The straw supplies plant fibre and structure, while the CVG can help retain water.

The straw should be:

• Clean

• Properly hydrated

• Suitably pasteurised or sterilised

• Cooled completely before inoculation

• Free from visible mould

The correct ratio will depend on the mushroom species and cultivation method.

For Oyster mushrooms, straw alone or straw combined with hardwood may provide a more predictable substrate than a mixture dominated by CVG.

Can CVG be used as a casing layer for other mushrooms?

CVG can be used experimentally as a casing layer for species that benefit from a moist, non-nutritious surface layer.

A casing layer can help:

• Maintain surface moisture

• Protect the colonised substrate

• Create a humid pinning environment

• Support developing mushrooms

• Reduce rapid surface drying

Not every mushroom species requires casing.

Oyster mushrooms, Lion’s Mane, Shiitake and Reishi normally fruit directly from their colonised substrate without a CVG casing layer.

What type of container should I use?

CVG can be used in a clean monotub, shoebox-style container or another suitable bulk-growing container.

The container should:

• Be clean

• Be large enough for the substrate and grain spawn

• Allow controlled gas exchange

• Retain humidity

• Have sufficient depth for the substrate

• Be easy to inspect without unnecessary opening

• Be suitable for the selected mushroom species

Avoid containers that have previously held chemicals, cleaning agents or unsafe materials.

How should I clean the growing container?

Wash the container thoroughly before use.

A basic cleaning process is:

1. Remove visible dirt and organic material.

2. Wash the container with warm water and detergent.

3. Rinse it thoroughly.

4. Allow it to dry.

5. Wipe the interior and lid with a suitable disinfectant.

6. Allow the disinfectant to evaporate before adding the substrate.

7. Handle the clean interior as little as possible.

Clean the surrounding working surface and wash your hands before mixing the CVG and grain spawn.

How do I mix colonised grain with CVG?

Prepare the growing container before opening either bag.

A practical process is:

1. Clean your hands, tools, container and working surface.

2. Confirm that the grain spawn is fully colonised and healthy.

3. Break up the grain inside its sealed bag.

4. Open the CVG only when ready to use it.

5. Add part of the CVG to the clean container.

6. Add the colonised grain spawn.

7. Mix the grain evenly throughout the substrate.

8. Add the remaining CVG.

9. Level the surface without compressing it heavily.

10. Close the container and allow colonisation to begin.

Even grain distribution helps the mycelium spread through the complete substrate.

How much grain spawn should I use?

The amount of grain spawn required depends on:

• Mushroom species

• Container size

• Amount of CVG

• Grain-spawn quality

• Incubation temperature

• Desired colonisation speed

• Contamination risk

Using more healthy grain spawn creates more inoculation points and usually results in faster colonisation.

A low spawn rate may take longer to colonise and gives competing organisms more time to establish.

For experimental gourmet cultivation, a generous amount of fully colonised grain spawn is generally more reliable than adding only a small quantity.

Can one 2 kg CVG bag be mixed with one 2 kg grain bag?

Yes, one 2 kg CVG bag can be combined with a fully colonised 2 kg grain bag for a relatively high spawn rate.

A high spawn rate can provide:

• Rapid colonisation

• Numerous inoculation points

• Strong nutritional support

• Reduced time before the substrate is fully colonised

However, the ideal ratio depends on the selected mushroom species and the growing container.

Do not use a grain bag that is only partly colonised.

Should I use a separate top layer of CVG?

A thin top layer of CVG can be applied after the grain and substrate have been mixed.

This helps cover exposed grains and may reduce surface drying.

A practical method is:

1. Mix most of the CVG evenly with the grain spawn.

2. Level the mixture gently.

3. Apply a thin layer of remaining CVG over the surface.

4. Cover all exposed grain.

5. Avoid compacting the top layer.

A separate casing layer may later be applied when using CVG for Portobello cultivation.

Should I compress the substrate?

The substrate should be levelled and gently settled, but not heavily compacted.

Heavy compression can:

• Reduce air spaces

• Slow colonisation

• Create poorly aerated areas

• Cause uneven moisture distribution

• Encourage bacterial problems

• Make it harder for the mycelium to spread

Lightly press the edges and surface only enough to create an even substrate depth.

The mixture should remain loose and airy.

How deep should the bulk substrate be?

A practical starting depth for many container-based grows is approximately 7 to 10 cm.

The ideal depth depends on:

• Container dimensions

• Mushroom species

• Amount of grain spawn

• Amount of CVG

• Moisture requirements

• Fruiting method

A very shallow substrate may dry quickly.

An excessively deep substrate can generate additional heat and may take longer to colonise.

Keep the depth as even as possible across the container.

Does the CVG need additional water?

The CVG arrives hydrated and ready to use.

Do not automatically add water before mixing it with grain spawn.

Excess water can create:

• Waterlogged substrate

• Poor aeration

• Slow mycelial growth

• Bacterial contamination

• Pooling at the bottom of the container

• Stalled colonisation

If the sealed bag has been stored for an unusually long period and appears dry, assess it carefully before use rather than adding an unmeasured amount of water.

What does properly hydrated CVG feel like?

Properly hydrated CVG should feel evenly moist without dripping heavily.

When a handful is squeezed firmly, it may produce only a small amount of water.

The substrate should not be:

• Muddy

• Soupy

• Dusty

• Completely dry

• Saturated

• Dripping continuously

• Surrounded by standing water

The coir and vermiculite should remain loose enough to maintain air spaces.

What should I do if the CVG seems too wet?

Do not add wet CVG to a growing container if water is visibly pooling or pouring from the substrate.

Excessive moisture increases the risk of bacterial contamination and reduces oxygen within the mixture.

If the sealed product appears unusually wet or damaged when received, photograph it and contact us before opening or using it.

Do not attempt to dry sterilised CVG by leaving it exposed to room air, as this can introduce contamination.

What should I do if the CVG seems too dry?

The product should arrive properly hydrated.

If the unopened bag appears unusually dry, inspect it for:

• A damaged seal

• A puncture

• Prolonged storage

• Excessive air loss

• Dry or hardened sections

Contact us before using a bag that appears damaged or significantly dried.

Adding unsterilised water directly to sterile CVG can introduce contamination.

What conditions are needed during colonisation?

The ideal colonisation conditions depend on the mushroom species.

A practical general starting range for many gourmet cultures is:

• Temperatures of approximately 20°C to 25°C

• A clean and stable environment

• No direct sunlight

• Controlled gas exchange

• Minimal disturbance

• Consistent substrate moisture

Some warm-growing species may prefer higher temperatures, while cool-growing cultures may perform better below this range.

The substrate can become warmer than the surrounding room as the mycelium grows.

A digital thermometer and hygrometer can help monitor the growing environment.

Does the container need to be kept in darkness?

Complete darkness is not normally required.

Low ambient light or ordinary indirect room light is acceptable during colonisation for many gourmet mushroom species.

Avoid direct sunlight because it can:

• Overheat the container

• Dry the substrate

• Create excessive condensation

• Cause major temperature fluctuations

Stable temperature and cleanliness are more important than complete darkness.

How long does CVG take to colonise?

Colonisation time depends on:

• Mushroom species

• Spawn ratio

• Grain-spawn health

• Temperature

• Substrate depth

• Container design

• Moisture content

• Gas exchange

• Contamination levels

Visible growth may begin within several days.

A high spawn rate may allow substantial colonisation within one to three weeks, while slower-growing species or lower spawn rates can take longer.

Do not introduce fruiting conditions based only on a fixed number of days.

Assess the actual condition of the substrate.

What does healthy colonisation look like?

Healthy mycelium is generally white or cream-coloured.

Depending on the species, it may appear:

• Fine and thread-like

• Cotton-like

• Dense and solid

• Rope-like

• Patchy during early growth

• Evenly spread across the surface

• Visible along the sides of the container

Healthy growth should gradually spread from the colonised grains into the surrounding CVG.

Unusual green, black, pink or foul-smelling growth may indicate contamination.

Should I mix or disturb the substrate during colonisation?

No. Once the colonised grain and CVG have been mixed and placed in the container, leave the substrate undisturbed.

Mixing during colonisation can:

• Break the developing mycelial network

• Introduce contaminants

• Delay recovery

• Cause uneven moisture

• Compact the substrate

• Damage developing fruiting structures

Inspect the container from the outside whenever possible.

Avoid repeatedly removing the lid.

When should fruiting conditions be introduced?

Fruiting conditions should be introduced after the substrate is sufficiently colonised for the selected species.

Signs may include:

• Mycelium visible across most of the substrate

• The mixture becoming held together

• No large uncolonised sections

• Clean, healthy growth

• No spreading contamination

• Species-appropriate maturation

Some species benefit from additional consolidation after visible colonisation.

Fruiting too early can leave uncolonised material exposed and increase contamination risk.

What fruiting conditions are required?

Fruiting requirements vary by mushroom species.

Most gourmet species require some combination of:

• Fresh-air exchange

• High humidity

• Species-appropriate temperature

• Gentle indirect light

• A fully colonised substrate

• Controlled evaporation from the surface

A practical humidity range during early pin formation is often approximately 85% to 95%.

Oyster mushrooms require frequent fresh-air exchange. Portobello cultivation requires cooler conditions after casing and careful moisture management.

Follow the requirements of the specific mushroom culture being grown.

Should I mist the CVG surface?

Mist only when the surface requires additional moisture.

Use a fine mist rather than pouring water directly onto the substrate.

The surface should appear moist without developing puddles.

Excessive misting can cause:

• Water pooling

• Matted mycelium

• Bacterial damage

• Stalled pin formation

• Overly wet substrate

• Mushroom damage

Once mushrooms begin developing, avoid repeatedly spraying them directly.

Maintain humidity in the growing environment instead.

Why are there water droplets on the container walls?

Condensation can form when the temperature inside the colonising container differs from the surrounding air.

Growing mycelium produces heat, and moisture may collect against the cooler container walls.

A moderate amount of condensation can be normal.

Heavy water pooling may indicate:

• Excess substrate moisture

• Large temperature changes

• Insufficient gas exchange

• Excessive misting

• An overheating substrate

• Bacterial activity

The surface condition of the substrate is more informative than condensation alone.

Why is the substrate not colonising?

Possible causes include:

• Grain spawn that was not fully colonised

• Weak or contaminated grain spawn

• Unsuitable mushroom species

• Temperatures that are too high or low

• CVG that is excessively wet

• Insufficient grain spawn

• Poor gas exchange

• Bacterial contamination

• Grain that dried before mixing

• Damaged or weakened mushroom culture

Check whether healthy growth is visible around the individual grains.

Do not add liquid culture to a stalled open container. This can introduce more moisture without correcting the underlying problem.

How can I recognise contamination?

Possible contamination signs include:

• Green mould

• Black mould

• Pink or red growth

• Rapidly spreading grey mould

• Slimy areas

• Sour or fermented smells

• Rotten odours

• Pooling liquid with stalled growth

• Uncolonised grain becoming wet or discoloured

• Mushroom mycelium stopping abruptly around another organism

Some mushroom species naturally produce cream, yellow or amber pigmentation, so colour alone should not always be used for diagnosis.

When uncertain, isolate the container from other cultivation projects.

What should I do with a contaminated container?

Do not open a heavily contaminated container inside the home or growing area.

Opening it can release mould spores.

A safer process is:

1. Keep the lid closed.

2. Move the container away from clean cultures.

3. Take it outdoors if it must be opened.

4. Dispose of heavily contaminated substrate safely.

5. Clean and disinfect the container before reuse.

6. Clean the surrounding shelf and work area.

7. Wash your hands after handling it.

Do not attempt to remove one visible patch of mould and continue the grow. Contamination may already be present throughout the substrate.

Can unused CVG be resealed and stored?

Opening the sterile bag exposes the remaining substrate to airborne microorganisms.

For the best results, use the full bag after opening.

If some substrate remains:

• Handle it as little as possible.

• Reseal the bag immediately.

• Store it in a cool, clean location.

• Use it promptly.

• Do not assume that it remains sterile.

• Inspect it carefully before use.

Dividing the bag across several projects increases the chance of contamination.

How should an unopened CVG bag be stored?

Store the sealed bag in a cool, clean and dry location away from direct sunlight.

Avoid:

• Freezing

• High temperatures

• Radiators

• Hot vehicles

• Direct sunlight

• Sharp objects

• Compression that may damage the seal

• Excessive handling

Use the substrate as soon as reasonably possible after delivery for the best results.

Does the CVG need refrigeration?

Refrigeration is not normally required when the sealed substrate will be used promptly.

Store it at a cool and stable room temperature.

Do not freeze the bag.

If the bag has been stored in a cool location, allow it to return to the appropriate cultivation temperature before mixing it with colonised grain.

Can the substrate be sterilised again?

Re-sterilising the substrate is not normally necessary or recommended.

A second sterilisation cycle can:

• Alter moisture content

• Compress the mixture

• Damage the packaging

• Change the physical structure

• Create excessively wet or dry areas

Use the substrate directly from the sealed bag.

If the bag has been opened, damaged or contaminated, re-sterilising it does not guarantee that it will perform as originally intended.

Can the CVG be reused after a grow?

Spent CVG should not be sterilised and reused for a new indoor cultivation project.

After the growing cycle is complete, healthy spent substrate can be:

• Added to a compost heap

• Mixed into garden soil

• Used as organic matter

• Added beneath outdoor mulch

• Used in an experimental outdoor mushroom bed

• Spread around ornamental plants

Remove any plastic or non-compostable material first.

Do not reuse heavily contaminated substrate in an indoor growing space.

Can spent CVG produce additional mushrooms outdoors?

A healthy spent substrate may occasionally produce additional mushrooms when placed outdoors under suitable conditions.

It can be:

• Buried beneath mulch

• Added to a shaded compost area

• Mixed with suitable fresh plant material

• Placed beneath shrubs

• Added to an outdoor mushroom bed

Outdoor fruiting depends on:

• Mushroom species

• Remaining nutrition

• Weather

• Rainfall

• Temperature

• Competition from other organisms

• Substrate moisture

Additional mushrooms cannot be guaranteed.

Is CVG suitable for beginners?

Yes. Prepared CVG removes several substrate-preparation steps and can simplify bulk mushroom cultivation.

You do not need to:

• Measure coco coir

• Measure vermiculite

• Add gypsum

• Calculate hydration

• Mix the ingredients

• Load the substrate into a bag

• Pressure sterilise it

• Cool it before use

However, the grower must still produce clean, fully colonised grain spawn and provide suitable conditions for the selected mushroom species.

Is successful mushroom production guaranteed?

No substrate can guarantee successful mushroom production.

Results depend on:

• The mushroom species

• Grain-spawn health

• Culture genetics

• Clean handling

• Spawn ratio

• Temperature

• Humidity

• Fresh-air exchange

• Lighting

• Container design

• Fruiting conditions

• Contamination control

The CVG provides a prepared growing medium, but mushroom cultivation involves living organisms and environmental variables.

Where is the CVG prepared and shipped from?

Our Sterilised Bulk CVG Substrate is prepared, hydrated, pressure sterilised and sealed in Ireland.

Each order contains one 2 kg bag of prepared coco coir, vermiculite and gypsum substrate.

Fast shipping is available to customers across Ireland, the UK, Europe, the United States and Canada.