The main purpose of grain spawn is to provide the nutrients and water as well as a physical surface for your mycelium to colonise prior to being added to a substrate mix. The grain spawn will usually be highly dense in nutrients, in comparison to substrate that will have a low to medium nutrient density. Due to this high nutrient content grain spawn needs to be effectively sterilised prior to use.

The advantage of grain spawn over a solid cake such as that used in the PF-Tek is that the grain spawn can be broken apart to spread the colonized grain throughout the bag or jar, this greatly reduces the time taken to fully colonise a vessel. Additionally when using grain spawn, grain to grain transfers can be performed, which can exponentially grow the number of jars you are working with producing much higher yields from a single syringe or agar plate.

The type of grain spawn you choose to use can vary, depending on your budget, and what is readily available for you. It is definitely worthwhile trying out as many types as possible to see how your results vary.  

For best yields the recommended grain for most types of mushroom is rye berries/rye grain. This is due to the nutritional makeup (it’s very dense in nutrients) of the grain along with its high water retention, meaning that it provides higher yields in comparison to some other grains. 

The main factors which will lead to variation between the performance of different types of grain spawn are:

  • Water retention 
  • Nutrition density and profile
  • Grain size
  • Ability to maintain integrity once sterilised

Below are the main factors to consider for each of the most popular types of grain spawn

Rye berry grain spawn in jar
– Hydrated Rye Berries

Using Rye Berries to grow mushrooms

If rye berries are readily available to you, they are definitely worth trying out. However by comparison to other readily available grains they are expensive to use. Health food/ organic food stores will often stock Rye Berries.

Rye berries have a great water retention capacity, in fact they are able to increase their size by 300% when hydrated. 

-Most importantly they can achieve this without becoming a mushy mess when placed under pressure and heat condition during sterilisation

– High nutrition density leads to high yields

– Small size allows for easy colonisation by mycelium , quick colonisation 

Steps to prepare Rye Grain

Using Brown Rice to Grow Mushrooms

-Brown rice is readily available at nearly every supermarket. If you cannot find whole oats or Rye berries, you will definitely still be able to find brown rice.

-Brown rice can hold water well, however is very easy to overcook when preparing, over hydrated rice is typically harder to work with as the grains will stick together.

The size of the brown rice allows for quick colonisation by the mycelium during colonisation.

Using Whole Oats to grow Mushrooms

whole oats grain spawn jar

Whole oats are a great economical grain spawn and they are used commonly as a food source for livestock and horses. It is readily available at fodder stores and many stores online in large 20Kg bags for affordable prices. A 20Kg bag will produce a lot of grain spawn. 

– Other types of oats (rolled, steel cut) aren’t suitable for grain spawn, make sure that you purchase whole oats (for animal consumption) with the hulls intact.

-Preparation guide for oats

Popcorn Grain

-Popcorn kernels are readily available and easy to find. The type found in the supermarket for human consumption are suitable for use as grain spawn

-Popcorn has great water retention

-Once disadvantage is its size. It’s the largest of the grains discussed here. This means that a jar containing popcorn will have a larger amount of grain, and lower amount of mycelium when fully colonised.

– Smaller surface area by comparison to smaller grains, leading to slower colonisation

See here for how to prepare popcorn grain spawn

Wild Bird Seed

Wild bird seed grain spawn jar

-WBS is a combination of grains, usually millet, milo and sunflower seeds.

-Wild bird seed is another alternative that is very easy to find, and is cost effective, it can often be purchased in large bags.

-Needs to be untreated bird seed, as to not contain any possible fungicides

-The different grain types can lead to inconsistency with hydration

-Very quick to hydrate ( can be hydrate with a couple mins in boiling water, or an overnight soak)

See here for how to prepare Wild Bird Seed Spawn

Overall Rankings

  • Best for Price: Whole Oats
  • Best Availability: Brown Rice
  • Best Yield: Rye Grain

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