People searching for "mushroom seeds" are looking for spawn. Mushrooms do not grow from seed; they grow from mycelium, the thread-like body of the fungus, and spawn is simply mycelium living on something you can handle and spread. For home growers that something is grain, because grain is cheap, nutritious, sterilises well and breaks into thousands of pieces, each of which carries a bit of the colony into the substrate.

Spores, culture and spawn

Spores

The fungus's seeds, in a loose sense. Microscopic, genetically mixed, slow and unpredictable to germinate. Used to breed new strains, not to grow food reliably.

Culture

A single, known, clean strain of mycelium kept on agar or in liquid. This is what you buy to start a grow: gourmet and medicinal cultures.

Spawn

That culture grown out onto grain. Bigger, stronger and spreadable. Sterilised grain bags become spawn once inoculated; colonised grain spawn already is.

How spawn is made

1. Grain is prepared

   Rinsed, soaked and simmered so every kernel is hydrated through without bursting, then drained to a precise moisture and enhanced with nutrients.

2. Bagged and sterilised

   Sealed in a filter-patch bag with an injection port and run through a full autoclave cycle at 121°C. Now nothing in it is alive.

3. Inoculated

   A few millilitres of liquid culture, or a wedge of agar, go in. This is the moment you do at home with a grain bag, or we do for you with colonised spawn.

4. Colonised

   One to five weeks in the dark at room temperature while mycelium runs through every kernel. A shake at a third colonised speeds it up.

What good spawn looks like

Bright white, every kernel coated, holding together in a loose brick that crumbles into separate kernels when you break it up. It smells clean and mushroomy. Rhizomorphic growth, thick strands running between kernels, is a sign of a vigorous strain; fluffy, cotton-wool growth is usually fine but slower. Anything coloured, wet, slimy or sour is not spawn, it is a bin bag.

How long spawn lasts

Spawn is alive and it is eating. At room temperature a finished bag stays good for a week or two before it starts to exhaust the grain and lose vigour. In the fridge, two to three weeks is comfortable and four is pushing it. Freezing kills it. The practical rule: order spawn for the week you will use it, and if you make your own, time the bag to finish when the substrate is ready. The storage guide has the detail.

Using spawn

• To substrate: mixed through coir or hardwood at 1:2 to 1:5 by weight. Ratio guide.
• To more grain: a few handfuls dropped into fresh sterilised grain in a still air box. One bag becomes five to ten. How to expand spawn.
• To an all-in-one: not needed; the all-in-one makes its own spawn from the culture you inject.

How much spawn is enough

A 1kg bag of spawn is the unit most tubs are planned around: at 1:2 it carries 2kg of coir substrate, at 1:4 it carries 4kg, and at 1:5 it spawns a 5kg hardwood block or two 2kg ones. A 2kg bag doubles each of those. Heavier ratios colonise faster and give contaminants less time; leaner ratios stretch the grain further. For a first grow, plan on 1:2 and let the grow builder turn that into bag sizes.

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.