Sold out

Extra Special (BulkMix) MycoBox Grow Kit


This grow kit has been superceded by our ‘Extra Special (BulkMix) MycoJar² Grow Kit’ which you can view here.
SKU: N/A Category:
This extra special grow kit is tuned to deliver the biggest flush sizes of any product we have ever offered.
Expect multiple large harvests until the substrate is completely spent of nutrients.
Recommended to anyone who loves their mushrooms, beginners and experienced alike!

From October 15th, we have been producing Rye Grain MycoBoxes with 1 injection port rather than 6.

Inoculation if you have 6 injection ports

  1. Give the bag a quick clean with the included wipe
  2. Slide the MycoBox out to reveal the first two injection ports
  3. Inject 0.5ml-1ml of a gourmet spore / culture syringe deep into each of the ports
  4. Repeat with with the remaining injection ports
  5. Place back into bag and leave MycoBox alone in a warm place to fully colonise
  6. Follow the rest of the guide until harvest

Inoculation if you have 1 injection port

  1. Give the bag a quick clean with the included wipe
  2. Slide the MycoBox out and inject 3-4ml of a gourmet spore / culture syringe into the port
  3. Shake the MycoBox to distribute the injected solution throughout the rye grain
  4. Place back into bag and leave MycoBox alone in a warm place to fully colonise
  5. Follow the rest of the guide until harvest

The white HEPA filters on the lids will filter dust and mould spores and allow clean air exchange. Don’t try to remove these!
NEVER open the MycoBox before full colonisation of mycelium or the kit will be ruined with contamination.

Click the ‘Instructions’ tab above to read our detailed guide
Includes photos of how to use the Bulkmix – it’s easy!

What’s Included

  • 1200ml MycoBox of Coffee-enhanced Organic Rye Grain Substrate and Gypsum (18x12x7cm)
  • HEPA-Filtered and Inject-Thru™ lid system for ultimate contamination resistance
  • XL Ultra Grow Tent to fruit your mushrooms inside (32x49cm)
  • 1 litre Bulkmix recipe of coir and vermiculite within a heat-sealed bag
  • Hygiene Kit includes surgical gloves, alcohol wipe and hand wipe
  • Online Guide

Not included

  • Gourmet Spore or Culture Syringe


If you cannot use your grow kit right away, we would advise that you store it in a (clean) fridge for a maximum of 2 weeks.
If you can’t store it in a fridge, don’t leave it for any longer than 1 week.
The longer you leave it, the more moisture will be lost from the substrate and if too much moisture is lost, colonisation will just not happen.

Always inoculate your grow kits as soon as you possibly can!


  • This grow kit is tailored for all experience levels, for our biggest results yet!
  • MycoBox can take anywhere up to 8 weeks to fully colonise at optimum temperatures
  • Packaging may contain a small build up of water – the distilled water is sterile and nothing to worry about.
  • Does not come supplied with a gourmet spore or culture syringe.
  • Some wood-loving species like Shiitake may not fruit on this substrate.


All grow kit products are for UK customers only at this time, sorry.
Product is made fresh to order – Please check our dispatch schedule here.
Only for use in cultivating species which are legal to grow – research the law.


Important update added to Stage 2 of this guide to prepare the BulkMix - Please read!

Instructions for Extra Special (BulkMix) MycoBox Grow Kit


For this stage, you will need:

  • 1 x Rye Grain MycoBox (supplied)
  • 1 x Surgical face mask (supplied)
  • 1 x Pair of sterile gloves (supplied)
  • Alcohol wipes (supplied)
  • Gourmet spores / liquid mycelium syringe and needle (not supplied)
  • Flame lighter (not supplied)

Make sure you and the room are clean and draft-free (no pun intended!). Fit your gloves and face mask - make sure your hands are clean and bone dry before fitting them or you won't get the gloves on, trust us! Use the alcohol wipe to thoroughly clean the rubber ports built into the tub (allow a few seconds to become visibly dry) and then pierce into each rubber port to inject the required amount of solution. Flame sterilize the needle between each other kit you may have purchased (if you haven't purchased extra needles from us). Now place the MycoBox back into the bag it arrived in to keep dust and other nasties off it - leave a gap in the seal so it can still breathe! Place somewhere at room temperature to begin colonising, they will turn completely white in time, so be patient. Don't put these tubs in any direct sunlight. When it looks complete, don't rush it - let it have another week.

1. Get organised

Choose a space to use as your 'lab' - An ideal room to use will be draft-free, such as a small cupboard. Kitchens and bathrooms are generally not suitable because of the increased risk of mould. Take everything you will need into your lab at this point, you want to keep air currents to an absolute minimum - close the door and keep it closed until you are finished! - to lower the odds of contaminant spores getting into the MycoBox.

2. Cleanliness

Take the time to ensure you are completely clean - have a shower, brush your teeth and change into fresh clothes. Before you begin the inoculation process, take your face mask out of the bag and secure it tightly to your face. Then, make sure your hands and forearms are clean - you can wipe them with the included Clinell hand wipe and let them completely air dry first or you'll struggle to put your sterile gloves on!

3. Inoculation
From October 15th, we have been producing Rye Grain MycoBoxes with 1 injection port rather than 6. If you have 6 injection ports - inject 0.5-1ml of solution into each port. If you have 1 injection port - inject 3-4ml of solution into the port and then shake the MycoBox to distribute the solution throughout the rye grain.

Give the syringe a good rattle and shake to help break any clumping. Remove the cap from the end of the syringe, unwrap the sterile needle and screw it on to the syringe. Thoroughly wipe the rubber injection ports on the MycoBox and allow them to dry before swiftly piercing the needle through and injecting the required amount of liquid into each port.

When inoculating other grow kits with the same syringe, it's advised to flame sterilise the needle until it glows red hot, giving 15 seconds or a tiny squirt of liquid to allow the needle to cool down before injecting. Or you could purchase some extra needles and switch them over if you prefer.

Never wipe a needle with an alcohol wipe - this will only sanitise it. It's best flame sterilising for proper sterilisation.

4. Colonisation

Now it's time to leave the MycoBox in a safe place to fully colonise with mycelium. We recommend that you place the MycoBox back into the bag it arrived in to keep it as clean as possible for the next stages. Remember not to seal the bag fully to allow the growing mycelium to breathe!

It's recommended to leave the MycoBox to colonise in a room with indirect sunlight or light from a flourescent bulb.. although a dark cupboard won't do any harm. Just keep it out of direct sunlight and it will be fine!

Regarding heat, many species love very warm climates during colonisation but it can be a balancing act because so do bacteria!.. If your mycelium is going strong, it can outrun many types of bacteria and you will never know they were even present.

Keeping the colonising MycoBox somewhere between 18C and 26C is ideal. 26C will be noticeably faster than 18C but with some patience it will get there regardless.

If you are determined to have a warmer environment for faster colonisation times, we strongly advise against the use of heat mats as they can dry out the bottom of the substrate and stall colonisation. It's a far better idea to store your substrates somewhere with more balanced heat like a warm cupboard above a fridge or near the water boiler..

Generally, you will start to see mycelium growth after 10 days depending on optimum conditions - if not, just hang in there a while longer as you may have injected too deep to see any growth yet.. Injecting gourmet spores or culture close to the walls of the container (tub in this case) is of course going to show quicker results than injecting deeper into the substrate - and that's the most common reason we get emails saying 'I can't see any mycelium..'. Patience is key here!

It normally takes around 6-8 weeks for the MycoBox to fully colonise with white mycelium and become what we refer to as a 'cake', but again, this depends on a range of factors such as temperature, genetics, etc.

When the MycoBox has reached full colonisation, it's highly recommended that you leave it for an extra week to allow the mycelium to consolidate within the core of the cake.



For this stage, you will need:

  • 1 x Bag of BulkMix (supplied)
  • 1 x Tent for fruiting your mushrooms in (supplied)
  • Scissors
  • 150ml water
  • Microwave
  • Tin foil


Some bags of BulkMix prepared prior to 1st October had been filled with 1.5 litres instead of 1 litre of substrate, which is too much and will take too long to completely colonise, potentially upping the chance of contamination.

If you ordered before 1st October, please mix in 250ml water before sterilising in microwave - but then only pour 1 litre of the substrate into the grow tent before mixing with your colonised grain (discard the rest).

If you ordered after 1st October, you can follow the guide as normal.

Cut a corner of the BulkMix bag
Pour 150ml of water in
Move the substrate around the bag to ensure the water is spread throughout
Shake the contents down, away from the opening in the bag
Place in your (clean) microwave, making sure that the hole you cut is open, to allow for steam to escape
Microwave on high for 10 minutes
Remove the bag from the microwave
Leave it to cool - wrap in foil to reduce loss of moisture
In a clean area and with clean hands, pour your cooled BulkMix into the provided grow tent
Take your colonised cake out of the MycoBox container and give it a rinse under a tap
Place your colonised grain into the bag and gently crumble with your hands - try not to burst/squash the rye grain kernels, just seperate them as much as possible
Take the time to fully break up and mix the colonised rye grain into the BulkMix
Fold the bag down, making sure that a white filter strip is not covered above the substrate (like in this photo) and secure with an elastic band


Now leave the substrate to fully colonise again in the same environment/temperature as before.

This takes up to 2 weeks in optimum conditions.


When the substrate is fully colonised, remove the elastic band and unroll the bag.

Open the bag and fan air inside - you can use anything to do this, like a piece of cardboard.

Ideally, you will want to open and fan into the bag a few times a day.

This process of introducing more air into the substrate promotes the growth of mushroom pins.

Another tip for allowing more fresh air into the bag is to leave the top of the bag slightly open, securing the majority of it with paper clips/pegs. Do not leave the bag fully open as this will release too much of the humidity and the substrate will begin to dry out.

If the substrate does appear to be drying out, you should lightly mist it with water.

But - unlike our other grow kits which use perlite at the fruiting stage, it is not necessary to continually mist inside the bag with water as there should already be enough moisture stored within the substrate mix to provide the required humid environment, to at least the first flush of mushrooms.


When your mushrooms are ready for harvest, you can just twist and pull them away from the substrate.

When you have harvested all of your mushrooms from your first flush, you can expect to see more fruiting! (If you have looked after your grow kit well, you should achieve a few large flushes of mushrooms.)

But, eventually the mushrooms will use up all of the nutrients within the substrate and no further mushrooms will be able to grow.

If you follow these instructions carefully, you will have no problem in growing your own beautiful mushrooms..

Good luck and have fun!