Interactive lesson

Spawn, step by step

Interactive lesson: how to choose, check and store spawn, and how to expand it yourself on cardboard and on grain in jars.

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The whole lesson as text

1. Forms of spawn

Spawn always grows on a substrate that is its food and carrier, and you choose the form by what you are inoculating.

Grain spawn — Rye, wheat, millet or sorghum. Most food and the fastest colonisation: for straw, coffee grounds, sawdust and beds.
Sawdust spawn — Hardwood sawdust, for logs and beds with wood chips. More natural for wood than grain.
Plugs — Wooden dowels of beech or birch, for logs and stumps. The simplest, but slower.
Liquid culture and agar — Liquid culture is for advanced growers, because its purity is hard to check. Agar in a Petri dish is lab work.

Why: Spawn is to mushrooms what transplants are to vegetables: everything that follows depends on it. Fresh, vigorous spawn colonises straw in two weeks and overpowers moulds.

For most homesteads it is enough to buy grain spawn for straw and beds, and plugs or sawdust spawn for logs.
Grain spawn attracts mice and birds, so keep it closed.

2. Buying and checking

Spawn is not something you pick up while you're at it: buy it fresh, from a producer with a clear label.

Label — Latin name of the species, strain, production date or use-by date, substrate and weight.
Date and delivery — Spawn should be no more than a few weeks old and arrive in the week you use it. In summer, in a cool box or by express post.
Good spawn — Dense and white, grains linked by white threads, smells of fresh mushrooms. The bag is intact, the filter dry.
Bad spawn — Green, black, orange or pink patches, slime, water at the bottom and a sour smell: don't use it. Never open a contaminated bag in the house.

Why: Old, overheated or contaminated spawn brings bags that never turn white and green mould. The shorter the journey from the producer, the fresher the spawn.

A little yellowish liquid and a few small mushrooms in the bag mean the spawn is mature. Use it right away.
A good producer can tell you how much spawn you need and at what temperature the strain fruits. If they can't, find another.