Using Colonised Grain Spawn

Using colonised grain spawn…

Unlike some of our other products, we generally assume that if you’re using colonised grain spawn bought from us, that you already know what you’re doing.

However, and just in case….

Colonised grain spawn is generally about as contamination-resistant as it is likely to get, but in practice you still need to follow sterile working and handling practices unless you plan to start your very own green mould farm.

For the benefit of those who haven’t tried using colonised grain spawn before, we have provided a simple guide below.

As always, patience is the key when using grain spawn. It takes a little patience to read up on what you need to know and do, adhere to sterile working techniques and to wait until harvest time arrives, but when it does, your patience will pay off!

Things you need to know..

Colonised grain spawn bags
We produce grain spawn mostly for ourselves and a local grower, but also make small quantities available for online customers. What you buy is taken from our own stocks. The grain will have been inoculated in one of 3 ways and may contain millet or slices of agar in addition to rye grain – this will depend on how the grain in the bags you buy were inoculated.

Inoculation
Inoculating grain is effectively the process of ‘seeding’ it by injecting it with inoculate material such as liquid mycelium culture. This has already been done.

Colonisation
When mycelium is added to a suitable food source such as rye grain it grows and colonises the grain. When the process is complete the grain will be fully covered with healthy white live mycelium. This is called colonisation. In order to bag colonised grain up into 1Kg bags, we break the grain up, then re-bag it. Although colonised grain is covered by white mycelium, this mostly vanishes when the grain blocks are broken up, which is why the grain you receive isn’t a solid white block. It’s perfectly normal. If you were to leave your grain spawn at incubation temperatures for a few days it would quickly start to go white again.

Using colonised grain spawn

Suitable Substrates
We supply several types of colonised grain spawn, some all year round and others only from time to time. As a general rule we only supply grain spawn for wood-loving species and so in most cases a hardwood-based substrate is recommended. To be sure you don’t waste your money, please look online at the various substrates that are suitable for the specific type of mushroom you plan to grow. We have added a quick list of commonly used substrates at the bottom of this page.

Blue Oyster Mushrooms
Blue Oyster mushrooms are a little different because although they are wood-loving mushrooms they will in practice grow on many types of substrate. Pasteurised straw and cardboard, or fresh coffee grounds are used by many growers with great success and at very low cost. It’s worth having a read up on this before starting out if you want to grow Blue Oysters.

Grain Spawn Storage
We would advise you to use your grain spawn within a couple of weeks from receiving it, but prior to use it needs to be kept in a cool place away from sunlight. A frdge is ideal, but temperature should be kept around 5-8C. Freezing spawn will kill it, so keep it away from cooling panels and freezer compartments in the fridge. Whilst in the fridge, the cool temperature dramatically slows down mycelium growth and prevents it overdeveloping.

Sterile Working
As always, sterile work practices must be observed. In addition to sterilsing your substrate, or buying it pre-sterilised, you must always ensure that any containers you put your spawn and substrate in are sterilised or at least disinfected with 70% isopropyl alcohol. Tools must be sterilised, gloves should be worn and as much as possible should be done to work in an environment with still air to reduce chances of unwanted contaminants floating into your mix.

Commonly-used substrates

Oyster mushrooms growing on straw

Oyster Mushrooms

Preferred Substrates:
Hardwood sawdust (often supplemented with bran)
Straw (wheat, rice, or barley straw, usually pasteurized)
Other choices – Agricultural by-products (e.g., corn cobs, cottonseed hulls, or coffee grounds)
Key Notes:
Blue oysters thrive in less nutrient-dense substrates like straw or cardboard.
King oysters prefer hardwood sawdust with additional supplements for optimal yield.

Lion’s Mane Mushrooms

Preferred Substrates:
Hardwood sawdust (oak or other hardwood species, usually supplemented with wheat or rice bran)
Soy hulls combined with sawdust
Sterilized logs for outdoor cultivation
Key Notes:
Lion’s mane benefits from a substrate with high lignin and cellulose content, favouring hardwoods.

Shiitake Mushrooms

Preferred Substrates:
Hardwood logs (oak and beech are most traditional and effective)
Hardwood sawdust blocks (usually enhanced with bran or other nutrients)
Key Notes:
Outdoor growers commonly inoculate oak logs for shiitake mushrooms, while commercial indoor growers use sterilized hardwood sawdust blocks for faster fruiting.

Shimeji mushrooms growing in bags

Shimeji (Beech) Mushrooms

Preferred Substrates:
Hardwood sawdust (with added wheat bran for nutrients)
Key Notes:
Shimeji mushrooms prefer a dense substrate and thrives on hardwood-rich mixtures.

Reishi Mushrooms

Preferred Substrates:
Hardwood sawdust (sterilized and enriched with bran or other nutrients)
Hardwood logs (oak or maple for traditional methods)
Wood chips or larger chunks of hardwood
Key Notes:
Reishi’s natural growth on hardwoods like oak makes hardwood-based substrates the optimal choice.

Common Themes

Hardwood sawdust, usually enriched with bran, is the most universal substrate across these species.
Species-specific differences include the preference for straw by oyster mushrooms and the need for denser hardwoods by shiitake and reishi.