Coco Coir (CVG) Beginner's Choice

Made from coconut husks. Usually mixed with Vermiculite and Gypsum (CVG). It is nutrient-poor, which makes it resistant to contamination.

✅ Pros:
  • Very resistant to mold (Trich)
  • Easy to prep (Bucket Tek)
  • Cheap and available
❌ Cons:
  • Lower yield potential than manure
  • Slower colonization

Manure (Dung) Pro / High Yield

Usually horse or cow manure, leached and aged. This is what Cubensis grows on in nature. It is nutrient-dense.

✅ Pros:
  • Massive yields
  • Huge fruits
  • Fast colonization
❌ Cons:
  • High contamination risk
  • Smell (during prep)
  • Requires proper pasteurization (Oven/Steam)

Straw Bulk / Outdoor

Pasteurized wheat straw. Great for wood-lovers and oysters, but also works for Cubes.

✅ Pros:
  • Extremely cheap (bulk)
  • Fast colonization
❌ Cons:
  • Messy to chop and prep
  • Prone to contamination if not perfect

Quick Comparison

Substrate Difficulty Contam Risk Yield Potential Best For
CVG (Coir) Easy Low Medium-High Beginners, Monotubs
Manure Hard High Very High Advanced, Max Yields
Straw Medium Medium High Outdoor beds, Oysters

Substrate Preparation: Step by Step

Each substrate type requires different preparation to reach the ideal moisture content, sterilisation level, and physical consistency for mycelium colonisation:

CVG (Coco Coir / Vermiculite / Gypsum)

  1. Mix 2 parts coco coir brick (expanded in boiling water) with 1 part vermiculite and 1/4 part gypsum by volume.
  2. Bring a kettle to boil and pour over the mix in a heat-safe container. Cover with foil.
  3. Allow to cool covered for 6-8 hours — this pasteurises without cooking. Gypsum acts as a pH buffer.
  4. Test field capacity: squeeze a handful — a few drops should emerge. Adjust moisture if needed.
  5. Use once cooled to room temperature (below 25°C) to prevent killing spawn on contact.

Pasteurised Manure

  1. Source horse or cow manure that has been aged and leached (odour mostly gone). Fresh manure has excessive ammonia levels that inhibit mycelium.
  2. Adjust moisture content to field capacity, then spread on baking trays.
  3. Pasteurise in an oven at 65-80°C for 2 hours, or steam in a large pot for 90 minutes.
  4. Allow to cool completely in a sealed container before inoculation. Do not rush this — hot manure kills everything.

Spawn-to-Substrate Ratios

The ratio of grain spawn to bulk substrate affects colonisation speed, contamination resistance, and yield. Higher spawn ratios colonise faster but reduce total yield per unit of substrate:

Spawn Ratio Colonisation Speed Contamination Risk Yield Best For
10% spawn Very slow (4-6 weeks) Very High Maximum (most substrate) Expert growers only
20% spawn Slow (3-4 weeks) High Very High Advanced growers
30% spawn Moderate (2-3 weeks) Medium High Most growers — good balance
50% spawn Fast (10-14 days) Low Medium (less substrate) Beginners, slow strains (PE)

Recommended starting point: 30% grain spawn to 70% bulk substrate. This is the most commonly cited ratio because it balances speed, contamination resistance, and yield across most strains and conditions.

Substrate Enrichment: Risks and Rewards

Adding nutritional supplements to bulk substrate increases yield potential but also raises contamination risk. The mycelium must colonise the substrate fast enough to outcompete competitors before they take hold.

  • Bran additions (wheat bran, oat bran): 5-10% by dry weight significantly increases yield. Must be fully pasteurised or sterilised. High nitrogen makes the substrate very competitive for contaminants.
  • Gypsum (calcium sulphate): 0.5-1% addition improves substrate structure, prevents clumping, and is widely used with no contamination downside.
  • Vermiculite: Improves drainage and aeration, reducing anaerobic pockets that bacteria exploit. No nutritional value but structurally valuable.
  • Coffee grounds (spent): Adds nitrogen and is already pasteurised by brewing. Mix at no more than 10-20% of total bulk substrate. Higher rates dramatically increase bacterial contamination.
  • Hydrated lime: Used in casing layers (not bulk) to raise pH above 8.0, which suppresses bacterial contamination while allowing mycelium to penetrate.
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