Grain gets a culture started; substrate is where the mushrooms actually come from. It is the bulk material you mix your grain spawn through, and it has to do three things: feed the species you are growing, hold water without drowning the mycelium, and let air through. Different species evolved on different food, which is why "what substrate" is really "what species".

The main substrates

Coco coir blends (CVA)

Coir for structure and water, vermiculite for air and buffering, minerals for trace nutrition. Forgiving, clean, easy to pack into tubs. The home-grower standard for oysters and compost-loving species. Our CVA.

Enriched coir (CVWA)

The same base with worm castings and Azomite added: the nutrition that older recipes got from manure, without the manure. Bigger flushes, slightly less forgiving. Our CVWA.

Hardwood pellets (HWP)

Compressed hardwood sawdust, hydrated and supplemented. What wood-decomposing species grow on in nature. The substrate for lion's mane, shiitake, king oyster, reishi and turkey tail, and a great one for oysters. Wood lovers substrate.

Straw

The traditional oyster substrate. Cheap, bulky, pasteurised rather than sterilised, and good for big outdoor-style grows. Not something we bag; mentioned because you will read about it.

Manure-based

Composted manure mixes for species that fruit on dung or compost. Variable, smelly, and replaced for most home growers by CVWA.

Substrate by species

Field capacity: the moisture that matters

Substrate should be wet enough that a hard squeeze of a handful yields a drop or two of water between the fingers and no more. Too dry and the mycelium stalls and the flush is thin; too wet and the bottom of the tub goes anaerobic, which is bacteria's favourite condition. Our bags arrive at field capacity, which is one of the quiet advantages of buying substrate: the mixing, the soaking and the squeezing are done.

Sterilised, pasteurised or neither?

Plain coir has so little nutrition that pasteurising it (65 to 80°C for an hour or two) is usually enough; nothing else can eat it quickly. The moment you supplement a substrate with bran, castings, soy hulls or minerals, you have made food that mould and bacteria will race for, and it must be fully sterilised at 121°C. Every bag we sell is supplemented and every bag is sterilised. The long version explains why that matters.

Tubs and blocks

Coir blends are usually grown in a tub: spawn mixed through, packed to 8 to 12cm deep, lid on, colonised in the dark, then opened to fruit from the top. Hardwood is grown as a block: spawn mixed through in the bag, the bag folded into a brick and colonised, then fruited from a cut in the side (lion's mane, king oyster) or the opened top (oysters, shiitake). The hardwood guide covers blocks; the coir guide covers tubs.

How much do I need?

A standard 50 to 60 litre tub takes 4 to 5kg of coir substrate at a sensible depth. At 1:2 that wants 2 to 2.5kg of grain spawn. A 2kg hardwood bag makes one decent block, or two small ones. The grow builder takes a weight and a ratio and picks the cheapest bags; the ratio guide explains the trade-offs.

Written by the Aus Myco Kingdom crew. Everything here is general growing information for gourmet and medicinal species; your room, your climate and your culture will have the final say.