Why CVG works.
CVG (coco coir + vermiculite + gypsum) is the de-facto standard for cubensis-class and oyster-class mushrooms grown indoors. It’s manure-free, pasteurizes reliably at 160–170°F for an hour, holds field capacity well, and the gypsum buffers pH against the metabolic acid drop that comes with active fruiting.
The standard recipe and why each ingredient is in it
- Coco coir (50% by volume): the structural matrix. Holds water, allows gas exchange, breaks down slowly enough to support multiple flushes.
- Vermiculite (50% by volume): pore-space and water reservoir. Releases moisture gradually back to the colonized substrate during fruiting.
- Gypsum (5% by dry weight): calcium sulfate. Buffers pH, supplies calcium for cell-wall structure, and gives the substrate texture so it doesn’t pack into a brick.
Adjusting CVG for your species
Pure CVG works for cubensis, oyster, and king oyster. For wood-loving species (Lion’s Mane, shiitake, chestnut), supplement with hardwood sawdust at 25–50% of the coir fraction. For fast colonizers needing extra nitrogen (Pioppino, some oyster strains), add 5–10% wheat bran or soy hulls and re-pasteurize accordingly.
Pasteurize, don’t sterilize
CVG is bulk substrate, not grain spawn. Full pressure-sterilization at 15 PSI is both unnecessary and counterproductive — it kills the beneficial competitor microbes that protect against contamination during fruiting. Pasteurize at 160–170°F for 60–90 minutes (cooler-method or steam) and you’re done. Use the Kineticist calculator to dial pasteurization holds for your altitude and equipment.