Mushroom Substrate Recipe Calculator

Build a tested substrate mix for your species and total bag count. Hardwood, supplements, water, hydration. Output: shopping list and prep instructions.

Build a substrate batch

Species Oyster (Pleurotus ostreatus / spp.) Lion's Mane (Hericium erinaceus) Shiitake (Lentinula edodes) King Trumpet (Pleurotus eryngii) Reishi (Ganoderma lucidum) Maitake (Grifola frondosa) Chestnut (Pholiota adiposa) Enoki (Flammulina velutipes) Pioppino (Cyclocybe aegerita) Turkey Tail (Trametes versicolor)

Number of bags

Bag size 3 lb (small / home) 5 lb (standard production) 10 lb (large block)

The substrate framework

Mushroom substrate has 4 components:

1. Bulk carbon (carbohydrate base): hardwood pellets, sawdust, straw, supplemented hardwood. This is what the mycelium eats.
2. Nitrogen supplement: wheat bran, soy hulls, oat bran. Adds N for the colonization phase. More supplement = bigger fruits but higher contamination risk.
3. Mineral supplement (optional): gypsum (CaSO₄). Buffers pH; provides Ca and S; flocculates surfaces for better water dynamics.
4. Water: hydration to ~60-70% moisture by weight. The number that determines whether your substrate works.

Common substrates by species

Species	Best substrate	Supplement	BE typical
Oyster	Straw or hardwood	None to 5%	75-150%
Lion's Mane	Supplemented hardwood	15-20% bran	50-100%
Shiitake	Supplemented hardwood	15-20% bran (oak best)	40-100%
King Trumpet	Supplemented hardwood	15-20% bran + soy hulls	60-150%
Reishi	Hardwood (oak)	10-15% bran	20-40% (slow grower)
Maitake	Hardwood (oak / maple)	10-15% bran	30-60%
Turkey Tail	Hardwood	10-15% bran	30-50%

BE = Biological Efficiency: weight of fresh mushrooms ÷ dry substrate weight × 100. A 100% BE means 1 lb fresh mushrooms per 1 lb dry substrate.

Sterilization vs pasteurization

Method	Time	Best for
Pressure sterilization (15 PSI / 121°C)	2-3 hours for 5lb bags	Supplemented hardwood; required when bran or other N supplement is added
Hot water pasteurization (160-170°F / 71-77°C)	1-2 hours	Straw substrates for oyster (no high-N supplement); cheap and lower-tech
Cold lime pasteurization	12-18 hours soak	Straw for oyster; outdoor / bucket production
Hydrogen peroxide / cold spawn	Instant; 1-2% H₂O₂	Hobby / small-scale; less reliable but no equipment

Critical: the field-capacity squeeze test

The single most reliable substrate moisture test:

1. Squeeze a handful of substrate firmly
2. Too dry: No water comes out. Add water.
3. Just right: 1-3 drops trickle out (not stream). Field capacity ~60-65%.
4. Too wet: Water streams out or drips continuously. Drain or add dry material.

This is more reliable than weighing because hardwood absorbs at variable rates. Hydrate, let sit 30 min, squeeze. Adjust.

Inoculation rate

Spawn rate	Time to colonize	Risk profile
2-3% (low)	~14-21 days	Cheap; higher contamination risk
5% (standard)	~10-14 days	Reliable for most species
10% (high)	~7-10 days	Fast; outcompetes contamination; expensive on spawn cost

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