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Grain spawn Rye grain: dry pale brown kernels spread evenly across the frame

Spawn & Substrates

Rye Grain (3kg)

Cleaned whole rye grain for making mushroom spawn. It holds water well, carries the nutrients mycelium needs, and the grains stay separate after sterilising so you can shake the jar to spread growth.

£5.00

Sold as dry grain. You hydrate and sterilise it yourself.

Whole rye
Cleaned cereal grain, no additives, you control the prep

Holds water
Soaks to field capacity for steady colonisation

Shakes loose
Spreads mycelium evenly through the jar or bag

GrainWhole rye

NitrogenAbout 2.3 percent dry weight

Weight after hydratingAbout 1.9x dry weight

Target moistureAbout 50 to 54 percent

UseGrain spawn base

WHAT IT IS

Why growers use rye for spawn

Rye is the most common grain for mushroom spawn because it absorbs and holds water well, carries useful nutrients, and most mushroom mycelium grows through it readily. Rye holds roughly 2.3 percent nitrogen on a dry weight basis, which supports vigorous early growth.

The grains stay separate after sterilising, so once colonisation is under way you can shake the container and spread the mycelium across the grain. Each colonised grain then acts as a starting point when you mix the spawn into a larger substrate.

HOW TO USE IT

Preparing rye grain spawn

The aim is grain hydrated to about field capacity, meaning the kernel is full of water but the outside is dry to the touch. Target moisture sits around 50 to 54 percent. As a rough check, 1 kg of dry rye comes out at roughly 1.9 kg once correctly hydrated.

Rinse and soak

Rinse the grain to remove dust and debris. Cover with water and soak for 12 to 24 hours so the kernels take up moisture before cooking.

Simmer briefly

Drain, add fresh water, bring to a boil and simmer for about 15 to 20 minutes. The grains should be hydrated but not split open.

Drain to touch-dry

Strain and let the grain steam off until the surface is dry to the touch while the inside stays moist. A simple check: grains placed on dry paper should leave no wet marks.

Load and sterilise

Fill jars or filter bags and sterilise in a pressure cooker at 15 psi. Allow about 90 minutes to 2 hours at pressure for grain, longer for large bags, and let it cool naturally before opening.

Inoculate and run

Once cool, add your culture using clean technique. Leave the jar undisturbed until you see solid white growth from the inoculation points, then shake once to spread it. When fully run, break it up and mix into bulk substrate, commonly at around 1 part spawn to 2 to 5 parts substrate.

Getting moisture right is the main thing. Too dry and the mycelium stalls; too wet and the kernels split during sterilising, which clumps the grain, cuts air exchange and invites contamination.

Grain	Whole rye
Target moisture	About 50 to 54 percent (field capacity)
Soak	12 to 24 hours
Simmer	About 15 to 20 minutes
Sterilise	15 psi, about 90 minutes to 2 hours
Spawn ratio	Commonly 1:2 to 1:5 into bulk substrate

STORAGE AND WHAT IT IS NOT FOR

Keeping it, and where it stops

Store the dry grain in a cool, dry place away from damp and pests until you prepare it. Hydrated and sterilised grain should be used promptly; colonised spawn can be held cool for a while before mixing into substrate.

This is the spawn-making stage only. Rye grain is not a finished fruiting substrate on its own, and it is not a casing layer. It is the carrier you colonise first, then add to bulk for fruiting.

Sources

Shroomery cultivation forum

Supplied for legal gourmet mushroom cultivation and microscopy use. You are responsible for the cultures you choose to grow.