Disclaimer: This guide is intended for growers wishing to produce edible or medicinal mushrooms in home cultivation. The described practices should always be adapted to the species grown and the applicable legal framework.
1. Introduction
The substrate is the true foundation of a successful mushroom culture. It is what feeds, hydrates, and supports the mycelium until fruiting. A poorly chosen or poorly prepared substrate can compromise an entire culture, even with the best spores or mycelium.
Some edible and medicinal mushrooms have specific substrate requirements. Certain species, like button mushrooms or shiitake, naturally grow in meadows rich in organic matter or manure. Growers then seek to best reproduce these growing conditions in a controlled way.
Among the simplest and most effective solutions, the CVG substrate (Coco - Vermiculite - Gypsum) has established itself as a reference choice for both beginner and experienced growers. Easy to prepare, economical, and very efficient, it is perfectly suited for home cultivation of many mushroom species: oyster mushrooms, pioppino, and other medicinal or edible mushrooms.
In this article, we offer you a complete and practical guide: you will deeply understand what the CVG substrate is, why it works so well, and above all, how to easily make it with the right materials. Ready to give your mycelium the best chances of success? Let’s go!
2. What is the CVG substrate?
The CVG substrate is one of the most used mixes for indoor mushroom cultivation. Its name comes from the three main ingredients that compose it: Coco Coir (coco fiber), Vermiculite, and Gypsum. Together, these materials create an ideal environment for the mycelium to quickly colonize and produce beautiful fruits.
Coco fiber: an ideal base for mycelium
Coco Coir, or coconut fiber, comes from the husk of coconuts. It effectively retains moisture while remaining light and airy, two essential elements for mycelium development. Using a coconut fiber substrate provides a stable structure, resistant to compaction, and naturally resistant to contaminants.
Vermiculite: for better water and air retention
The Vermiculite is an expanded mineral that plays a key role in substrate balance. It improves water retention without making the mix soggy, and also promotes good air circulation. A coco vermiculite substrate thus ensures an environment that is both moist and well-oxygenated, perfect conditions to stimulate mycelium growth.
Gypsum: to enrich and stabilize the substrate
Gypsum (calcium sulfate) is often added in small amounts to stabilize the substrate’s pH and prevent it from becoming too acidic over time. It also provides calcium and sulfur, two nutrients that strengthen mycelium health. In a mycelium substrate, gypsum discreetly but effectively contributes to more abundant harvests.
3. Why choose a CVG substrate?
The CVG substrate has established itself as a reliable choice for mushroom growers, whether beginners or more advanced enthusiasts. Here’s why this simple mix remains a strategic choice for successful cultivation.
An excellent water retention capacity
Thanks to coconut coir and vermiculite, the CVG substrate maintains an ideal moisture level for mycelium development without becoming waterlogged. This water stability reduces the risk of drying out or excess water, two common causes of failure in home mushroom cultivation.
A low contamination rate
Unlike other substrates richer in organic matter (such as manure or straw), the coconut mushroom substrate is low in nutrients for unwanted bacteria. This makes it a cleaner, more stable medium, and easier to secure with simple pasteurization. CVG is therefore an excellent choice for those who want to avoid contamination.
Great adaptability
The CVG substrate is suitable for a wide variety of mushrooms: oyster mushrooms, psilocybes, reishi, lion’s mane, etc. It can be used as is or enriched to suit the specific needs of a species. It is a versatile, reliable, and easily modifiable support. However, it is generally more used for coprophilous mushrooms (those that grow on manure or near cow/horse dung, for example) than for lignicolous mushrooms (which decompose wood).
A simple and quick preparation
No need for complex equipment or long composting steps: CVG is easily prepared with accessible ingredients. A good coconut fiber block, vermiculite, a bit of gypsum, hot water… and you get a quality substrate ready to be colonized.
Quality ingredients = quality cultivation
The success of a CVG substrate also depends on the quality of the materials used. Clean, well-fluffed coconut fiber free of contaminants is essential. It is with this in mind that the Mycosphere Coconut Fiber Block was designed: a reliable, practical product perfectly suited for fungal cultivation.
4. Product focus: Mycosphere coconut fiber 🌱
To obtain a quality CVG substrate, the choice of ingredients is crucial, and it all starts with good coconut fiber. That’s why Mycosphere coconut fiber is particularly suited for demanding growers.
Our coconut fiber block is 100% natural, without chemical treatment or additives. This ensures a clean, healthy, and mycelium-friendly support, with no risk of unwanted residues.
Easy to handle, the compressed block is compact, lightweight, and stores easily, even in a small space. Just hydrate it to obtain an aerated, fluffy, and perfectly textured coconut fiber: ideal for preparing a balanced coco vermiculite substrate.
Whether you are a beginner or an enthusiastic grower, the Mycosphere Coconut Fiber Block provides a reliable base to start your cultures under the best conditions.
The ideal coconut fiber block for your CVG substrate!
Our 100% natural coconut fiber is perfect for preparing a high-performance substrate. Untreated, easy to store thanks to its compressed format, it offers an optimal texture after hydration.
Discover the product5. How to prepare your CVG substrate? (Step-by-step guide)
Preparing your own CVG substrate is simple and rewarding. Here is a clear tutorial to succeed every time.
Necessary materials
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1 compressed coconut fiber block (like the Mycosphere Block)
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2 liters of medium or fine vermiculite
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50 g of gypsum (optional but recommended)
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Hot water (not boiling)
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A large clean container
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A spoon or shovel for mixing
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Clean gloves (optional)
Preparation steps
1. Hydrate the block of coconut fiber
Place the ingredients in a bucket, pour boiling water, close tightly and let rest. You can also cover the bucket with a blanket to extend the pasteurization time. Always wear protective gloves to avoid burns during this operation.
Work in a clean area. After 6 to 8 hours of cooling, mix vigorously to homogenize.
Little advice: crumble the coconut fiber well with your hands to avoid the formation of "compact chunks" that would hinder colonization.
2. Add vermiculite and gypsum
When the coconut fiber is well moistened and aerated, add the vermiculite and gypsum.
Tip: lightly sift the vermiculite if it contains large pieces to achieve a more homogeneous texture.
3. Mix thoroughly
Mix everything by hand (with clean gloves) or using a shovel.
The goal is for the vermiculite and gypsum to be distributed uniformly throughout the coconut fiber.
Quick reminder: a homogeneous mixture ensures better colonization of the substrate by the mycelium.
4. Adjusting moisture ("squeeze test")
Take a handful of the mixture and squeeze it tightly in your hand:
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If a few drops of water bead between your fingers, it’s perfect.
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If water runs freely, it’s too wet: add some dry coconut fiber or vermiculite.
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If nothing grows and the mix is crumbly, add a little water.
Tip: use a spray bottle or a rain-like water jet to finely adjust moisture without soaking the substrate.
Substrate made of a mix of hydrated coconut fiber, grains, and gypsum, just before being sterilized in a pressure cooker. Adding grains increases the substrate’s richness, and thus its potential productivity, but it also raises contamination risks because bacteria also love the sugars present in the grains.
6. Pro tips for an even better CVG substrate
Even though the CVG substrate is simple to prepare, a few tips from experienced growers can really make a difference. Here’s how to maximize your chances of success.
Always check moisture with the "squeeze test"
Substrate moisture is one of the most critical factors. After mixing your CVG, always perform the "squeeze test":
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Squeeze a handful of substrate in your hand.
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A few drops should bead without running.
If it’s too wet, the mycelium can suffocate or allow contaminants to take hold.
If it’s too dry, the mycelium will struggle to colonize the substrate.
👉 Take your time to adjust the moisture. This small effort at the start can make all the difference!
Do not pack the substrate too tightly
When bagging or placing in a tray, it is important to not compact the CVG substrate too much.
Mycelium needs oxygen to breathe and grow. If the substrate is too dense, it slows colonization and increases the risk of rot.
Tip: gently tap the substrate so it fits the shape of the container without ever forcing or crushing.
Should gypsum always be used?
Gypsum is very useful, but not mandatory in all situations:
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Use it if you want to stabilize the pH for long cultures (Reishi, etc.) or enrich your substrate with calcium.
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You can omit it for fast-growing cultures like some oyster mushrooms or psilocybes.
👉 When in doubt, adding a bit of gypsum is often a risk-free "plus".
Adapt the CVG according to the cultivated species
Each mushroom species has its little preferences:
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Oyster mushrooms: prefer a slightly more aerated and lighter substrate (add a bit more vermiculite to lighten the texture).
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Coprophilous medicinal mushrooms: love the classic structure of the standard CVG.
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Wood-decay mushrooms (Reishi, Lion’s Mane): prefer a slightly more humid substrate sometimes enriched with additional nutrients, mainly based on wood sawdust.
Tip: by finely adjusting the texture and moisture to the cultivated species, you can achieve faster and more generous harvests.
Can you enrich your CVG substrate?
Although the standard CVG substrate is already very effective, it is possible to enrich it to obtain more abundant harvests, especially with certain demanding species.
Enrich with sterilized grains
The addition of sterilized grains (such as rye, wheat, or millet) in the CVG substrate provides additional nutrients, rich in sugars and nitrogen. This stimulates colonization speed and can improve production.
Warning: an enriched substrate is also more attractive to contaminants (bacteria, molds). It is therefore essential to handle the grains in ultra-clean conditions and ensure perfect sterilization.
Enrich with pelletized manure
Composted and pasteurized pelletized manure (horse, poultry, etc.) can be incorporated in small amounts to enrich the substrate. It improves nutrition without overly weighing down the texture, provided not to exceed 5 to 10% of the total volume as pelletized manures are often very concentrated.
Tip: favor horticultural quality pasteurized pellets to limit risks.
Enrich with coffee grounds
Coffee grounds can be used to enrich the substrate with nitrogen, which generally promotes more vigorous mycelium growth and more abundant harvests. It can improve the nutritional structure of the substrate and support the development of many saprophytic species.
It is recommended to incorporate about 10 to 20% of the total substrate volume.
Be careful though: coffee grounds are a highly contaminable material.
It must be used fresh (ideally within 24 hours after extraction) if kept at room temperature, as it quickly becomes colonized by molds and bacteria.
To limit risks:
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use fresh grounds,
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work cleanly,
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or store it in the freezer until you have enough to prepare your substrate.
Once thawed, use it immediately and avoid refreezing.
A tip for beginners
If you are a beginner, it is recommended not to enrich your CVG substrate. A simple substrate is more stable, less risky, and much more forgiving in case of mistakes.
You might harvest a little less, but you will maximize your chances of success and satisfaction by avoiding losing everything due to contamination.
7. Quick FAQ
Should I pasteurize my CVG?
Yes, it is highly recommended to pasteurize your CVG substrate, especially if you work in a non-sterile environment. This reduces contamination risks and gives the mycelium a head start.
What is the best coconut fiber for making CVG?
A 100% natural coconut fiber, untreated chemically and well loosened, is ideal. The Mycosphere coconut fiber block is specially designed for this use.
Can vermiculite be replaced by something else?
Vermiculite is hard to replace because it combines water retention and aeration. Otherwise, you could try perlite, but the result is often less optimal for fungal cultivation.
Is gypsum really necessary?
Gypsum is not mandatory, but it stabilizes pH and provides nutrients useful to the mycelium. It is especially recommended for long cultures or enriched substrates.
How long can I keep my prepared CVG?
The CVG substrate can be stored for 1 to 2 weeks in a clean airtight bag, kept cool. It is important to check that it does not dry out or develop suspicious odors before use.
8. Conclusion
The CVG substrate is a simple, reliable, and effective solution for successful home mushroom cultivation. Thanks to its water retention capacity, low risk of contamination, and great adaptability, it stands out as a valuable ally for both beginner and experienced growers.
The ideal coconut fiber block for your CVG substrate!
Our 100% natural coconut fiber is perfect for preparing a high-performance substrate. Untreated, easy to store thanks to its compressed format, it offers an optimal texture after hydration.
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