Rye Grain vs Millet vs Popcorn: Drain the Grain Jane

A word about contamination

If you’re looking to grow mushrooms regularly then it’s inevitable that you'll encounter contamination at some point in your journey. If you spot any signs of it then it's highly recommended to dispose of the culprit immediately ensuring clean environment, avoiding any cross-contamination of your tubs, bags or grain. Throughout, it’s best practice to be clear and methodical with your processes - I guarantee that you'll benefit from higher, healthier yields.

Detecting contamination early is critical to healthy cultivation

We won’t be able to cover all the contaminants here but look out for discolouration, green, yellow or brown spots or streaks on the surface, a foul odour, abnormal growth, moulds, growths on the surface of the mushrooms & insects. One of the most common causes of contamination is caused by the improper sterilisation of the grain spawn so it’s best to use an autoclave. The International Journal of Applied Sciences and Biotechnology _[1] states that autoclaving is:

reported to yield better in many substrates compared to a chemical method and most of the experiments on mushroom are found to prefer substrates sterilised in an autoclave due to its superiority in terms of biological efficiency and reduction in contamination.

Comparing contamination risk

Millet is a small grain with a hard outer shell that provides a natural barrier against contaminants. Its small size means a high surface area to volume ratio, which allows for more inoculation points for the mycelium. However, the downside is that its compactness can lead to moisture content issues if not properly hydrated. Ensuring even hydration is critical to prevent contamination. Proper sterilisation and clean handling practices are essential to mitigate these risks.

Rye grain is a common option used in mushroom cultivation, in part, due to its relatively low contamination rates. The larger size of Rye grains compared to millet means fewer inoculation points, but they are easier to hydrate evenly. Rye grains' robust structure and nutrient-rich composition provide an excellent medium for mycelium growth. Contamination risks are lower if proper sterilisation procedures are followed, making it a reliable choice.

Popcorn, while not traditionally associated with mushroom cultivation, has gained popularity due to its availability and ease of use. The large size of popcorn kernels means fewer inoculation points, which can lead to slower colonisation compared to millet and rye. Popcorn's low contamination rate is one of its advantages, as its dense structure makes it difficult for contaminants to penetrate. However, ensuring even hydration and avoiding overly wet kernels are crucial to prevent contamination.

I want my grain spawn to colonise quickly

Millet's small size and high surface area to volume ratio facilitate more rapid mycelial colonisation. The numerous inoculation points provided by the tiny grains allow the mycelium to spread quickly, often resulting in faster colonisation compared to larger grains. This rapid colonisation can outcompete potential contaminants, further reducing contamination risks. For those looking for a faster turnaround, millet is a suitable choice.

Colonisation can vary greatly for grain spawns

Rye grain offers a balance between colonisation speed and ease of handling. While not as fast as millet, rye grain still supports relatively quick mycelium growth due to its favourable nutrient profile and structure. The larger grains provide ample space for mycelium to grow, leading to robust and healthy colonisation. The slightly slower speed compared to millet is offset by the reliability and consistency that rye grain offers.

Popcorn's larger kernel size means fewer inoculation points, leading to slower colonisation compared to Millet. Once colonisation begins, the mycelium tends to grow vigorously within the kernels. The slower initial colonisation can be a disadvantage if a quick turnaround is desired, but for those looking for a more forgiving substrate, popcorn's ease of handling and lower contamination risk can be worthwhile.

I need grain that’s simple and easy

Preparing Millet can require careful attention to hydration levels. There are simpler methods which involve preparing it an autoclavable bag. This is achieved by just adding roughly half the amount of water to substrate and sterilising in an autoclave for a longer period. The small size of the grains makes it easy to overhydrate or underhydrate, which can impact mycelium growth and contamination risk. The most common method is to soak the Millet then simmer to achieve the correct moisture content before sterilisation.

If Millet is simmered for too long the grains will burst the outer shell which presents, not only an inconsistent product, but also a higher risk of contamination. This process can be somewhat labour-intensive, yet with practice, you can achieve consistent results. It’s common to fan the grains post simmer to ensure they are not overly hydrated prior to being sterilised at pressure.

We stock Organic Rye Grain, sterilised and ready to go

Rye grain is relatively straightforward to prepare. It involves soaking the grains for up to 24 hours, then boiling them to achieve the desired moisture content.

Drain the Grain Jane

After boiling, the grains should be drained and allowed to steam dry before being sterilised. On a family holiday not long back, I remembered that I had forgotten to drain the grain from a bag that I was prepping and if I didn’t want to waste it, then it couldn’t wait. I called up my mother-in-law, Jane, who was looking after the place, but I had a terrible signal. And in my attempts to get the message across, found myself shouting repeatedly down the phone “drain the grain Jane, drain the grain Jane” – a family anecdote to which we often refer.

The preparation process for Rye grain is well-documented and widely explored. A simple method to test if the grain is ready is to place a handful onto some tissue paper. If there is no residue then you are good to go, essentially the grain should be dry to touch before being placed in an autoclave or pressure sterilisation chamber.

Popcorn is one of the easiest substrates to prepare. The kernels can be soaked overnight and then simmered until they reach the appropriate moisture content. After simmering, they should be drained and allowed to steam dry before sterilisation. The simplicity of this process, along with the robustness of popcorn kernels, makes it an appealing choice for those new to mushroom cultivation or those looking for a less labour-intensive mushroom grain.

Will my grain provide enough nutrients for the mycelium?

Millet provides a rich nutrient profile that supports vigorous mycelium growth. Its small size and high surface area ensure that the mycelium has ample access to nutrients, promoting healthy and rapid colonisation. Millet is particularly effective for smaller species of mushrooms that benefit from the numerous inoculation points. However, its use requires careful attention to moisture levels to prevent contamination and ensure optimal growth.

Popcorn isn't just a favourite cinema snack

Rye grain supplies a balanced nutrient composition, which supports a wide range of mushroom species. The larger grain size provides a stable structure for mycelium growth, and the grains' robust nature helps retain moisture effectively. Rye grain's nutrient profile and ease of preparation make it a versatile and effective grain spawn for both common and specialty mushrooms that contribute to its popularity.

Popcorn, while not as nutrient dense as Millet or Rye, still provides a suitable grain spawn for mycelium growth. Its effectiveness lies in its ease of use and lower contamination risk rather than its nutrient profile. Popcorn is best suited for beginners or those looking for a low-maintenance approach. Its larger kernel size and ease of hydration make it a practical choice, though you may need to supplement it with additional nutrients like gypsum for optimal results.

So what's the best grain spawn?

Choosing the right grain spawn for mushroom cultivation involves considering several factors, including contamination risk, colonisation speed, ease of preparation, and nutrient effectiveness. Millet offers rapid colonisation and a high nutrient profile but requires careful hydration management. Rye grain provides a balanced and reliable option with moderate colonisation speed and ease of preparation. Popcorn, while slower to colonise, offers simplicity and lower contamination risk, making it ideal for beginners.

Ultimately, the choice of grain depends on your environment, availability, experience level, mushroom species and the desired outcomes. Hopefully now you have a better understanding of the unique characteristics of Millet, Rye grain, and Popcorn, so you can make informed decisions that enhance your mushroom cultivation experience.

The role of Substrates in Mushroom Cultivation

Why use substrates and do they need nutrients?

The choice of substrates can be very simple in many cases. The mycelium holds all the necessary nutrients while the substrate is a carrier for moisture. A significant proportion of the fruiting body of a mushroom is moisture (roughly 90%). Coco coir is an excellent substrate for this reason. It’s extremely contaminant resistant, absorbs high quantities of moisture and is simple to hydrate.

We offer premium grains and substrates

Field Capacity is a term used to describe the optimal level of moisture retention required for a substrate _[2]. You can simply test field capacity by squeezing the substrate. The desired outcome is for a small amount of moisture to be released. Coco-coir can be mixed with Perlite or Vermiculite if you want to use something to help aerate the soil plus provide additional moisture retention.

Previously it was thought that a nutrient rich substrate was required, however, this is not the case. Humidity plays a huge role in the pattern and speed of growth within the fruiting stages of a mushroom’s lifecycle.

There is a significant relationship between humidity, transpiration and hydration during fruiting _[3]. Studies have found that increased humidity leads to faster growth rates, lower transpiration and an increased yield due to a higher available moisture content. The caveat to this is that with higher temperatures the risk of contamination is increased. There is always a balancing act as nature constantly reminds us. Although mushrooms require indirect sunlight the study showed that increased light bared no impact on the speed and size of growth.

How does Substrate relate to my Grain Spawn?

Firstly, it’s important to understand the ratio of spawn to substrate. As the study suggests, higher moisture translates to bigger mushrooms. Increased humidity leads to faster growth. You can adjust the ratio of spawn to substrate to help you optimise the required moisture for each species grown. A good starting point is a 3:1 ratio. Some species, especially those that blob, require a higher ratio.

Experts agree, moisture levels are a critical attribute of mushroom substrate, influencing nutrient absorption, otherwise greatly determining the overall success of cultivation _[4]. So your growing environment must retain moisture effectively to reduce the potential of your substrate drying out. It must also allow fresh air exchange in order to clear the build up of Co2 that lingers on the surface of the soil generated by the decomposition of organic matter by the mycelium.

Nutrient rich substrates can be extremely effective. Horse manure is one good example. It is easily available and there’s often stables and such that give it away as an organic fertiliser. It is best to break up and wash, allow it to dry in order to remove the ammonia before rehydrating and pasteurising.

Pasteurisation destroys many of the unwanted pathogens while retaining some of the more friendly bacteria. The results of using horse manure can be very promising, however, there are more significant challenges to growing in this way. Notably contamination and moisture retention. If you’re experienced and want to experiment further, it can be an exceedingly productive option or additive to your substrate.

Subtrate summary

Coir based substrates offer all the advantages of a lower risk of contamination, high water retention and simple to hydrate and there is a heap of documented recipes online. Manure based substrates are more complex. They may provide mushrooms with additional benefits, however, more scientific research and further evidence is needed. A major advantage is that it’s readily available in the countryside and often cost-free.