Millet Grain Sterilised – For Mushroom Spawn

We invest significant time and resources to ensure our parcels are securely packaged and reach you safely and undamaged.

If your item requires a box, it will be shipped in a discreet, plain, sturdy, double-walled cardboard box of appropriate size, with unbranded packaging tape and ample internal protection to prevent damage during transit. While accidents are rare, they can occasionally happen.

Smaller, sturdy, and lightweight items will be sent in plain, unbranded padded envelopes.

All pallet orders are professionally strapped, wrapped, and equipped with corner protectors.

We also strive to minimize excessive packaging to help protect the environment.

Scroll down to see a section on our Shipping & Returns info, with links out to our policies

Yes, we can accommodate your needs for any custom orders, substrate / grain mixes, special requests etc. Generally speaking, anything which is considered to be a custom order will have a bespoke price. Please contact us to discuss options.

As an online-focused business, we prefer digital payments. However, for orders over £500, we do accept cash payments. Please contact us to process your order and arrange collection.

We do not provide a standard collection service for orders under £500. If your order exceeds £500 and you wish to collect it, please contact us. Please note that, due to our insurance policies, we are unable to allow public access to our warehouse or offer tours of our facilities.

Each order comes with the quantity of bags ordered, one instructional guide and one set of alcohol wipes per order. Please leave a note at checkout if you require additional instructional guides or alcohol wipes. You will need to purchase a liquid culture of your chosen mushroom strain separately.

A copy of our instructional guide can be downloaded here: Sterilised Grain Bag Instructions

Note, that a printed hardcopy of the instructional guide will be included with your order.

There are numerous ways of growing mushrooms, and will depend on your experience, available equipment and time availability. At a minimum, you will need to purchase the following in addition to your grain bag(s):

Liquid Culture – A mushroom liquid culture of the strain you want to grow. (You may also use a spore syringe, but we do not recommend it due to the higher risk of contamination)

Substrate – You will need to decide on the most suitable substrate for the mushrooms you are growing. Substrate is required to mix with colonised grain spawn to ensure a successful yield.

Fruiting Chamber (optional) – Different strains of mushrooms like to grow in different ways. Popular set-up examples are a monotub, a shotgun fruiting chamber, a ‘martha’ style humidity chamber where mushrooms are grown on trays or blocks, or even on suspended straw columns in a temperature and humidity-controlled room.

If you’re looking to fruit mushrooms in the bag, you can take a look at our All-in-One mushroom growing kit which will allow you to do just that.

We highly recommend doing some research on what mushroom cultivation method will best suit you. A good resource is the ‘Shroomey forum’ – it has a wealth of cultivation advice on growing most strains of mushroom and an active forum of cultivators who can share their experience and knowledge.

We recommend using 1-2ml of liquid culture per 1.5kg bag of grain (or approx 0.5-1ml for 750g bag).

The approximate sizes and volumes of our grain bags are as follows:

• 1.5kg – 15cm x 12cm x 12cm (approximately 2.16 litres or 2.28 quarts (US measurements)
• 1.2kg – 15cm x 12cm x 10cm (approximately 1.8 litres or 1.9 quarts (US measurements)
• 750g – 11cm x 8cm x 11cm (approximately 0.97 litres or 1.0 quarts (US measurements)

We offer a 30-day, 100% sterility guarantee. We highly recommend leaving the bags for 1-2 weeks from delivery to validate their sterility before use. We strongly advise using the bags immediately after this period, as all bags are susceptible to contamination due to the nature of the bag having a filter.

Sterilised grain bags are best stored at room temperature and left packed in the box in which they came in. This should stop excessive amounts of air or moisture escaping from the filter. Do not store them in the fridge or freezer, as this could cause excessive condensation in the bag, making your grain over-saturated.

We recommend leaving the bags 1-2 weeks before inoculation as a precautionary measure to self-validate the sterility of the grain. If there are no signs of contamination after 1-2 weeks, you can be assured that your bag is still perfectly sterile as it should be and is ready to use.

Although we have multiple checks to ensure all the grain leaves us in perfect condition, on rare occasions, they can become damaged in transit and subsequently become contaminated. If this does happen, please contact us, and we will arrange for a replacement to be dispatched. Please keep hold of the contaminated bag, as we might need more information from it before we can dispatch a bag to you.

Due to the high risks of contamination during inoculation, please note that we do not offer refunds or replacements for any bag that has already been used.

To make our kits, we first triple-rinse the grain to remove dust or chaff. Next, we soak them overnight in a purified water + gypsum solution to partially hydrate the grains and allow any endospores to activate; adding gypsum provides additional nutrients to the grain, which supports healthy mycelial growth and also stops grains from becoming clumped together.

The partially hydrated grains are then slowly brought to a boil until the grains are hydrated to precisely 55%. We quickly drain the boiling water and immediately distribute the grain on our outdoor drying racks, leaving them to steam off and cool.

This process removes any excess external moisture, resulting in perfectly hydrated grain, which is dry to the touch.

The resulting grain is then weighed into genuine Unicorn bags, double-sealed and processed in our industrial autoclave on an extended 125°C cycle for 3.25 hours to ensure all contaminants are killed off.

Once allowed to cool slowly, the bags are individually checked to ensure they are perfectly sterile and only then do we allow them to be dispatched to our customers.

We have provided sterilised grain and grow kits to hobby growers and commercial operations for a number of years. Whilst it’s difficult to put an exact number on it, we know it’s in excess of 100,000 grain bags. We have also sold countless sterilised substrate bags during our years in business.

The time it takes for a bag to fully colonise will depend on many factors. The type and quality of your culture, whether you’re growing from spores or liquid culture, temperature, and even lighting conditions can affect colonisation rates.

3 – 6 weeks on average for full colonisation, we would expect to see growth in a bag usually within a week if you’re using a high-quality liquid culture. Inoculating grain bags with spores can be notoriously unpredictable, with germination rates sometimes taking over one month alone.

Different mushroom strains will have different yield expectations. Yields are generally calculated via biological efficiency. Some mushroom strains can produce five or more times that of others, so we can’t give a single answer.

Whilst we do our best to remove all traces of foreign matter from our grain, on rare occasions, a very small stone might find its way into our bags from harvesting the grain. This will not affect the bag in any way, nor the colonisation of the mycelium.

Small white clumps within the odd bag will be clumps of gypsum, which we add to the grain.

Gypsum adds essential minerals to the millet grains and can be used as a supplement at almost all stages of mushroom production. Gypsum also aids in stopping the individual grains from sticking together in the bag, allowing for faster and more healthy colonisation – with less chance of contamination.

This is totally normal; discolouration can occur due to how the bags are loaded into the autoclave and left to cool after the sterilisation cycle.

Condensation forms in the bag due to fluctuating temperatures during shipping; this is totally normal. The grain can be mixed to allow it to reabsorb the condensation. It should be left for one week before inoculation. The included instructions provide more information on this.