How To: Easy Straight In The Bag Grain Spawn | Spore Light

How To: Easy Straight In The Bag Grain Spawn | Spore Light

Easy straight in the bag grain spawn!

Mushroom cultivation requires a sterile environment to prevent contamination and ensure the growth of healthy mycelium. One way to achieve this is by using a variety of sterilized grains to create a spawn bags. The mayority of mushroom growers use rye berries, oat seeds or groat oats, sweet corn, pop corn among others. This will provide an excellent substrate for mycelium growth. For convenience in this guide, we’ll walk you through the steps to make sterilized grain spawn bags with rye berries in a clean and safe environment but reducing the amount of steps to streamline the process.

Materials Needed:

  • Rye berries
  • Pressure cooker or autoclave
  • HEPA flow hood or laminar flow hood (Alternatively a still box)
  • Spawn bags with a 0.2 micron filter
  • Distilled water
  • Gloves
  • Mask
  • Alcohol spray
  • Impulse sealer

Step 1: Prepare the Rye Berries

Begin by selecting high-quality rye berries for your spawn bags. Rinse the rye berries in a strainer under running water to remove dust or debris. Add the unsoaked rye berries directly into the spawn bags.

Step 2: Sterilize the Rye Berries and Spawn Bags

Add enough distilled water to the spawn bags to cover the rye berries.

Our rule is 1:1 weight ratio to fully hydrate the rye berries, this is specially important for sclerotia producing species.

Fold the extra plastic on the top of the spawn bags over and underneath the block of berries and water to fit it inside the pressure cooker.  Make sure the filter ends up facing inward and is not exposed.

Add the spawn bags to the pressure cooker or autoclave. Ensure a metal plate or ring separates the bags from touching the bottom of the cooker.  Also, add water to the bottom of the pressure cooker until it almost touches the bags, filling the gap between the bottom of the cooker.

Bring the pressure up to 15 psi and cook for 2 hrs or 120 minutes to ensure that the rye berries and spawn bags are fully sterilized. Make sure that the temperature doesn't exceed 255F. Sterilization occurs at 250F.

Why Rye Berries?

Nutrient content: Rye berries are a nutrient-rich substrate that provide a good source of carbohydrates, proteins, and minerals for mushroom growth. They are also relatively low in fat, which is important for preventing contamination.

Consistency: Rye berries are relatively consistent in terms of moisture content and particle size, which is important for ensuring even colonization by the mycelium. This can help to reduce the risk of contamination and improve overall yield.

Availability: Rye berries are widely available and affordable, making them a popular choice for mushroom growers.

Compatibility: Rye berries are compatible with a wide range of mushroom species, making them a versatile substrate for mushroom cultivation.

Easy to prepare: Rye berries are relatively easy to prepare for sterilization, and can be cooked and hydrated quickly and easily.


Mushroom cultivation: Sterilized spawn bags can be used as a starting material for growing different types of edible or medicinal mushrooms. The bags contain a substrate that is inoculated with mushroom spores or mycelium, which then colonizes the substrate to produce fruiting bodies.

Mycelium propagation: Sterilized spawn bags can also be used for propagating mycelium, which is the vegetative part of the fungus. Mycelium can be used for various purposes, such as for research or for the production of bioactive compounds.

Spawn production: Sterilized spawn bags can be used to produce spawn, which is the material used to inoculate larger volumes of substrate for mushroom cultivation. Spawn bags are inoculated with a small amount of mycelium, and once the mycelium has colonized the bag, it can be used to inoculate larger volumes of substrate.

Tissue culture: Sterilized spawn bags can also be used for tissue culture, which involves growing fungal tissues in a sterile environment. The bags can be used to grow mycelium or to culture mushroom tissues for research purposes.

 Potential issues to be aware of:

Contamination: Contamination is the most common problem when making your own sterilized spawn bags. Even a small amount of contamination can cause the entire bag to fail, and it can be difficult to pinpoint the source of contamination. Some common contaminants include bacteria, mold, and yeast.

Improper sterilization: If the bags are not sterilized properly, contaminants may survive and grow inside the bag. This can happen if the bags are not heated for long enough, the temperature needs to be higher, or the pressure needs to be higher.

Incorrect moisture content: The moisture content of the rye berries is important for successful mushroom cultivation. If the rye berries are too dry, the mycelium may not be able to grow properly. If the rye berries are too wet, they may become soggy and lead to contamination.

Poor quality spores or mycelium: If the spores or mycelium used to inoculate the bags are not of good quality, they may not be able to colonize the substrate properly. This can result in slow growth, weak mycelium, or failure to colonize the bag.

Inadequate air exchange: The bags need to be ventilated to allow for gas exchange. Without enough air exchange, the mycelium may not grow properly and the bag may become contaminated.

To minimize the risk of these problems, it is important to follow a reliable and tested method for making sterilized spawn bags and to take all necessary precautions to maintain a sterile environment during the process.

Good luck!


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