Grain Spawn vs Sawdust Spawn

I see a lot of confusion when it comes to Grain Spawn vs Sawdust Spawn. The title of the blog is a bit misleading because this isn’t a competition of pros and cons to find out which is better. Grain spawn and sawdust spawn are both important in the arena of mushroom cultivation.

You almost can’t have one without the other unless you are a low-tech mushroom farmer. If you are looking into indoor cultivation with a sterile lab this is worth knowing. Even if you don’t plan on making your own and just want to buy it regularly this isn’t a subject you want to skip.

You will want to be able to spot the good quality stuff. On top of that, you will want to be able to ask the right questions about how it is prepared. You will want to know how to prepare spawn in case you can’t find a reliable vendor with any in stock.

How to prepare spawn is beyond the scope of this blog post. What you will learn here is the differences between the two types of spawn. You will learn that each type is necessary for the cultivation process.

Grain Spawn

Grain spawn is typically the first phase of spawn-making after the culture stage. It is called grain spawn because it is made from some type of grain or seeds. For example, we make our grain spawn from whole cereal rye grains. There is a procedure that we follow that prepares them to be inoculated with mushroom mycelium.

Cultures can be used to inoculate grains or fully colonized grains spawn can be used to inoculate more grains. When using grains spawn to inoculate more sterilized grains is called grain to grain transfers or G2G. The purpose of grain-to-grain transfers or G2G is to expand your mycelial mass.

What it means to expand your mycelium mass is to take a small amount and make it bigger. For example, say you have a quart jar of fully colonized grain spawn. If you want to make this small amount of grain spawn into a larger amount of grain spawn you would perform grain-to-grain transfers.

Ganoderma Lucidum mycelium colonizing rye grains.

Plan for your needs

You can take your one-quart jar of fully colonized spawn and inoculate ten more jars. Then you can take those jars and each one can inoculate ten more. After everything fully colonizes you have 100-quart jars of grain spawn. You are not required to produce this amount of grain spawn. No pressure.

You will want to produce enough to meet the needs of your operation. You will also want to be careful how much grain spawn you produce from a single jar or bag. Let’s say you have one jar of grain spawn made from a culture. This grain spawn is known as G1, 1st Gen, or 1st Generation.

When you take G1 grain spawn and perform grain to grain transfers, the next round of grain spawn will be known as G2, 2nd Gen, or 2nd Generation. Some texts recommend not expanding beyond G3, 3rd Gen, or 3rd Generation when producing spawn because your mycelium may experience cellular degeneration or what is also known as senescence.

Sawdust Spawn

Sawdust spawn is sawdust that has been supplemented, hydrated, sterilized, and then inoculated with grain spawn. A fully colonized sawdust block has multiple options. You can fruit directly from the block itself, produce more sawdust spawn, prepare outdoor mushroom beds, inoculate pasteurized bulk substrates, or even plug logs.

Sawdust spawn is typically the final stage in the spawn-making process. One of the excellent benefits of sawdust spawn is it is inexpensive to prepare. You can make your own sawdust or acquire some at a very cheap price. Hardwood sawdust is highly recommended.

To supplement sawdust there are a variety of options. Oat, wheat, or rice bran have been popular choices in the past. In modern times, soybean hulls and grain flours like barley are becoming more and more popular among cultivators.

Most of the gourmet mushrooms we enjoy today are wood decomposing fungi. Lion’s mane, Shiitake, Nameko, Enokitake, King Oyster, and Maitake are but a few of the suitable species for making sawdust spawn.

Oyster species such as Pearl, Gold, Pink, and Blue are also suitable for making sawdust spawn. But these species will also grow on various agricultural waste and organic debris. So they aren’t just considered wood decomposing fungi.

Pleurotus Eryngii Sawdust Spawn freshly broken up

The Mushroom Cultivation Process

A quick overview of the mushroom cultivation process might help rid you of confusion. Knowing where in the process the different spawns are made will help create a deeper understanding.

Even if you only plan to buy spawn and never work with cultures it is still considered foundational knowledge to at least have an understanding of the steps involved.

Step One: The culture stage

Beginning with healthy cultures with good genetics is crucial. You will always want to begin with strong cultures that are free from contamination. The culture stage is paramount so always work with a vendor you trust. Even if you only purchase spawn from them.

They are preparing spawn from their own culture library. If what you are looking for in your fruitbodies isn’t written in its DNA you will most likely not see those results. Not all strains are created equal.

In the culture stage, it starts with petri dish cultures, liquid cultures, and culture slants, starting the wild clone process. We work with a lot of petri dish cultures so we can observe the mycelial growth, test and preserve strains, etc. This also gives us the opportunity to produce our own liquid cultures.

Some acquire a liquid culture and they may first want to transfer to a petri dish. When you transfer to a petri dish, you produce petri dish cultures from liquid culture. This is excellent if you want to preserve a strain and/or produce grain spawn in bulk because a 10 ml syringe of a liquid culture will only produce so much spawn.

There are cultivators who prefer to order liquid cultures and inoculate prepared grains right away. Since liquid cultures are typically inexpensive they don’t mind placing recurring orders for more liquid cultures in the future.

Step Two: Preparing grain spawn

After the culture stage, it is time to prepare grain spawn. This is done by transferring your mushroom culture to prepared and sterilized grains. This can be done in a couple of ways.

One way is by simply using your scalpel to cut wedges from a petri dish and transferring those wedges to the sterilized grains. Another option is to create liquid culture from your petri dish culture. From here you can load syringes or free-pour the liquid culture directly into your prepared grains.

After inoculation places your grains on a shelf away from direct sunlight. The length of time they take to fully colonize the grains will vary by species and strain. After grains are fully colonized they can be broken up to where individual kernels become new inoculation points for the next stage of the process.

The next step can be g2g transfer, but it is optional. As mentioned earlier this is where grains spawn can be expanded into more grain spawn. But, you don’t want to overproduce and have more than you can use. You also will not want to repeat this step too many times and experience cellular degeneration in your spawn.

For the sake of this article, we will consider all grain spawn production in step two.

Pleurotus Ostreatus grain spawn freshly broken up.

Step Three: Sawdust Spawn

Your grain spawn is fully colonized and you have no interest in expanding it to more grain spawn. It is now time to prepare sawdust spawn. This is done by breaking up your grain spawn and pouring a portion of it into your sterilized supplemented sawdust.

After you have inoculated your supplemented sawdust with grains spawn you will want to thoroughly mix it through. This way you’ve reduced the distance that each inoculation point will have to colonize before reaching a neighboring colony.

These colonies will network together and after complete colonization will become a united mycelial mass. Since each inoculation point, contain mycelium that shares identical genetics they grow together and become one.

Once full colonization has been reached it’s time to execute your plans to begin the fruiting stages. This can be done by fruiting directly from the sawdust block itself or preparing logs, pasteurized bulk substrates, plugging logs, mushroom beds, or producing more sawdust spawn.

Hypsizigus Tessellatus Sawdust Spawn fully colonized.

Craft Of The Cultivator

It’s important to remember there is no one way or method to cultivate mushrooms. However, having a foundational understanding of the basic principles will go a very long way. Understanding the mushroom lifecycle, grain spawn vs sawdust spawn, cultures vs spores, and basic definitions of mycology should definitely be a part of your mental toolbox.

I understand how overwhelming the information can be and how arrogant some experienced cultivators are. The last thing I want is for you to quit because you are having difficulties navigating through the mushroom jungle of information.

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