At Home Gourmet Mushroom Cultivation: The Bucket Technique
My mushroom love affair probably began in Denmark, Western Australia after a visit to the Valley of the Giants souvenir shop where (out of a sore lack of reading material) I purchased the Department of Wildlife’s “What Mushroom is That?: Fungi of the South Western Forests”.
I’m not exactly sure whether it was the amusing names such as “velvet black earth tongue” and “curry punk” that grabbed me, their perfectly bizarre array of forms and colours, the charmingly nerdy descriptions of the author (“when dry, the fruit bodies smell of fenugreek”), boredom, or a combination of all four, but one thing is certain: from then onwards, I was an incorrigible Mycophile.
What follows here is an attempt to share a small slice of the wonder and joy visited upon me by that incidental fungi pamphlet, in the form of actionable instructions for growing an edible species at home. This article is by no means intended to be definitive, there are just about as many variations of mushroom cultivation method as there are mushroom species!
Rather, it functions as a brief how-to guide for replicating the procedure I used to grow my mushrooms, together with some (hopefully) helpful conceptual information.
Happy Reading!
An indispensable resource for my writing this was the Milkwood permaculture book by Kirsten Bradley & Nick Ritar.
*It’s a fantastic book (it’s also very pretty) — please read it.
Part 1: Concepts
The amateur cultivation of mushrooms inside food-grade buckets is an under-utilised yet effective technique. Part of the lack of uptake may be due to the perceived over-technicality of the process, which requires sterile conditions and some specialised equipment.
Admittedly, preparing the buckets did involve substantial forethought on my part, however it was far from unmanageable despite 0 prior mushroom growing experience. Also, once mastered, the basics don’t change!
c1 Pasteurisation
An important concept for would-be mushroom growers to understand is that of pasteurisation. Defined at the most basic level, mushrooms are microorganisms. This means they can be impacted by the growth of competing microorganisms like bacteria or even other types of fungi. Pasteurisation is a technique performed in the early stages of cultivation to ensure the mycelium gets a head-start relative to any unwanted by-beings lying latent in the substrate.
Substrate pasteurisation is probably the most unwieldy part of any mushroom-growing endeavour, because it involves heating a large quantity of water and keeping it within a narrow temperature band for an extended duration of around 2–3 hours. Exposure to elevated heat (between 60–80 degrees C) is what strips the growth medium of potential life, leaving an environment hospitable to mycelial colonisation.
Because pasteurisation involves manipulating large volumes, the first item to locate is a (or series of) sturdy plastic storage container(s) around 40–80L in size. When surveying your options, try to pick those likely to be the most heat-conserving: opaque, insulated and made of strong (non-flimsy) plastic.
If mere choosiness doesn’t placate your brain’s neurotic side, you can take your choosiness to the extreme by calculating the container’s heat-loss coefficient. Success with this step may require an obliging Mechanical Engineer and dusting off an ancient MECH ENG 3102 Heat Transfer and Thermodynamics textbook.
The output of this calculation will tell you whether the hot water in your tubs should remain within the desired temperature range long enough to achieve successful pasteurisation, conditional on both the external and internal temperature of the environment and the density index of your containers.
Unfortunately for my lofty dream of empirical reassurance, the heat-loss function we observed displayed a temperature slope that decayed below the minimum before the passing of 2 hours — hardly comforting!
Despite this disappointing verdict, if you live in a reasonably warm climate you can likely get away with an outdoor pasteurisation without the need for additional heating.
Alternatively, if you live in a particularly cold climate or are in the depths of winter, consider moving your substrate indoors to minimise heat loss and/or planning to pasteurise on a sunny day. Some fungi aficionados light small wood fires or camping burners underneath 44 gallon drums, securing their substrate with a wire mesh frame — however I’m far from convinced this step is always necessary.
To heat my water I hired a 20L electric urn for the weekend, splitting the task into two manageable batches. Fortunately, the urn had a temperature dial which could be set to exactly 80C, eliminating the need for time consuming manual measurements. If mushroom cultivation is likely to be a frequent future activity, it might be worth investing in your own electric urn (complete with time-saving temperature dial)— most sell second-hand for around $150–200.
c2 Substrate
Another make-or-break aspect of mushroom growing is the selection of a growth medium or — to use the technical-lingo- a substrate. An intuitive way to think about the role of the substrate is as “food” for the maturing spawn. Especially intuitive when you learn that mushrooms are vexatiously fussy eaters, and prefer different substrates depending on their type.
Straw, sawdust, wood chips, spent coffee grounds, manure and combinations of these materials together are commonly used as substrate. For my substrate, I used a ratio of 3 parts hardwood redgum sawdust to 1 part chopped straw (a veritable Oyster mushroom banquet). Softwood sawdust from coniferous species like fir and pine should be avoided as such species produce anti-microbial resins that hinder mushroom growth.
Unfortunately, my mycelium was unusually slow to both proliferate and fruit on the redgum mixture. Granted a do-over, I would have used oak or alder sawdust (common hardwood substrates) in addition to increasing the substrate’s straw-sawdust ratio.
c3 Spawn
Crazily, mushroom spawn can be bought over the internet and shipped to your home address. Most spawn consists of sterilised grains (e.g. whole oats) that have been inoculated with a petri dish culture and sealed in a vacuum package.
I ordered my spawn from Aussie Mushroom Supplies — a company based in Carrum Downs, Victoria, following a positive review from a friend — but there is no shortage of online suppliers and it may be worth shopping around.
Pleurotus Ostreatus — that’s Pearl Oyster to you — is popular among growers for its rapid growth and low-maintenance, characteristics that have earned it a reputation as the beginner’s ‘shroom of choice. A tangential sidebar: master spawn bags are not the same as regular spawn bags. Apart from being over 3x as expensive, they are a higher generation strain capable of expanding to ~100 spawn bags. Make sure you ask your supplier about this difference before buying, because — unless well versed in fungi-speak — it won’t be immediately apparent.
Importantly, if there is likely to be a substantial interval between the arrival of your spawn and the day you pack your buckets, store it in the refrigerator. This will prevent — or at least postpone — the spawn from gobbling up the available energy stores with free abandon and then joylessly turning on its own tissues in a spectacular frenzy of self-cannibalism. Surprisingly grizzly, I know. It’s a mushroom-eat-mushroom world out there…*
c4 Fruiting
The optimal conditions for fruiting vary with the ‘shroom in question. Some species demand highly controlled air flow, humidity and temperature levels, while others are relatively indifferent.
Because I packed my buckets in wintertime —when there is naturally ample moisture in the air — and most Oysters fruit successfully across a wide temperature range (yeah, Oysters!), darkness was the only necessary provision.
The shed was my logical third thought (after the knee-jerk bedroom and bathroom), and the buckets did seem quite content nestled between our family surfboard and a stack of old garden stakes.
Part 2: How To
Materials
- 40L water (at 80C)
- 1 cup hydrated ‘builder’s’ lime (calcium hydroxide)*
- 4 old pillowcases
- 4 metres strong polyester rope
- Duct tape or micropore surgical tape
- Protective equipment — water resistant garden gloves and dust mask
- 4 11L polypropylene (food-grade) plastic buckets
- Series of sturdy plastic storage containers
- 30L substrate (2 parts hardwood sawdust, 1 part chopped straw)
- 2.2kg Pleurotus Ostreatus Grain Spawn
- 1/2 inch drill-bit (or approximate)
- Clean (preferably new) tarpaulin
Method
- Prepare your buckets. Using the 1/2 inch drill-bit attachment (or approximate), create spaced holes all the way around each bucket. Cover each hole with a length of micropore tape so no air can get in.
Notes: For visual reference, see the photo of my packed fruiting buckets. These are the holes your mushrooms will fruit from, so it’s important to provide sufficient growth room.
2. Add cold water to your substrate until it is entirely damp. Don’t over-add such that it becomes flooded, just enough to ensure all surfaces are clearly wet.
Notes: Make sure that the water reaches the inner surfaces of your substrate. This will allow the heat from the urn water access to the substrate’s centre, guaranteeing a more thorough pasteurisation.
2. Gear up. Wearing your protective equipment, add the cup of Builder’s Lime to your substrate, making sure it is mixed evenly throughout.
Notes: Builder’s Lime is caustic. For those of you who flunked chemistry or need a reminder, this means it can corrode organic tissue i.e. YOUR BODY, hence the glasses and gloves. (…my lawyer told me to say this)
3. Pack the substrate into your pillowcases. Divide the substrate evenly between the four pillowcases, tying 1m of rope around the open end of each.
Notes: You will use the rope ends later to suspend your pillowcases for drying, so make sure there is some slack reserved for this purpose.
4. Pack the pillowcases into the pasteurising containers. Place a weighty object (dirt-free cinder block or brick) on top of each bag so they can be easily submerged. Pour the hot urn water into the containers until all bags are completely covered. Replace the lid on the container and weigh it down with another clean heavy-object.
5. Lunch! (or dinner, depending on your work rate — I don’t judge)
6. Hang the substrate out to drip drain. Remove the soaked pillowcases from your containers (careful, if you’re lucky they’ll still be hot enough to scald) and suspend them so the excess water drips freely away. I suspended my bags from the central beam of our outdoor pergola. Proceed to squeeze and wring (punch, beg, chastise — whatever works) the bags until they are no longer dripping.
Notes: Time is money (or mushrooms) here: try to complete the draining process as quickly as possible. During this stage the substrate is at heightened risk of microbial occupation.
7. Combine the spawn and substrate. Spread out the substrate onto a clean tarpaulin (yes — in the *open air*), and wait until it is barely warm (not hot, I repeat: not hot) to the touch. Once barely warm (not hot, I repeat: not hot) to the touch break apart the spawn block with your hands and then spread it throughout the substrate until evenly incorporated.
8. Pack your buckets. Simply transfer the substrate from the tarpaulin to your buckets, and then replace their lids.
9. Wait⁴ (Wait x Wait x Wait x Wait). Store your buckets in a dark, unlikely-to-be-disturbed location while you wait for the mycelium to proliferate. Once the substrate has been fully colonised — its surface should be completely covered in cloudy white fluff — go ahead and remove the tape from the fruiting holes. The addition of air will catalyse the fruiting stage. Timelines can vary, but I waited around 3–4 weeks before doing this.
Mushroom Eye Candy
(because who doesn’t love the part with pictures?…)
