• Hardwood Sawdust And Organic Wheat Bran Mix Close Up
  • Two bags of dry mushroom substrate including organic wheat bran
  • Shiitake Fruiting On A Hardwood And Organic Wheat Bran Block
  • Reishi Forming On A Fruiting Block With Hardwood Pellets And Organic Wheat Bran
  • Reishi Antlers Forming On A Fruiting Block With Hardwood Pellets And Organic Wheat Bran
  • Hardwood & Organic Bran Mix For Mushroom Substrate Kai Kai Farm
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Hardwood & Organic Bran Mix For Mushroom Substrate

Hardwood & Organic Bran Mix For Mushroom Substrate

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The classic hardwood-and-bran block recipe for shiitake and reishi — pre-weighed, pre-blended, ready to hydrate.

This is a ready-to-hydrate supplemented sawdust substrate: 80% Australian hardwood and 20% organic wheat bran by dry weight, with gypsum added at 5%. It’s the time-tested formula for wood-loving species that want more nutrition than plain hardwood can give them — shiitake and reishi in particular — and it adapts easily for turkey tail.

We blend it from the same 100% Tasmanian Oak hardwood pellets we use in our own production on Tamborine Mountain. No weighing out bran, no sourcing gypsum, no guessing ratios. Add water, bag it, sterilise, inoculate.

What’s in the mix — and why

Australian hardwood — 80%

The structural base

100% Tasmanian Oak hardwood pellets — Australian grown and manufactured, with no glues, binders or additives. Hardwood provides the cellulose, hemicellulose and lignin that wood-decomposing species are built to digest, plus the open, airy texture mycelium needs for gas exchange.

Organic wheat bran — 20%

The nitrogen boost

Pure hardwood is low in nitrogen. Bran adds protein, starches and minerals that fuel faster, denser colonisation and heavier flushes. 20% is the long-standing standard supplementation level for shiitake and reishi blocks — enough to feed the mycelium without tipping the substrate into contamination territory.

Gypsum — 5% of dry weight

Calcium, sulphur, better texture

Gypsum (calcium sulphate) supplies calcium and sulphur, and helps keep a bran-rich substrate from clumping and going pasty once hydrated. The result is a looser, more even substrate that the mycelium can move through cleanly. It’s already mixed in — nothing to add.

Blended on our farm

The same mix we fruit on

This isn’t a theoretical recipe. The shiitake and reishi in our product photos were grown on this exact blend. If a batch doesn’t colonise and fruit properly in our own grow room, it doesn’t go in the bag.

What you’ll notice
  • Dense, well-knit blocks that hold together through the long colonisation shiitake and reishi need
  • Stronger flushes than plain hardwood — the bran gives the mycelium the reserves to fruit hard
  • Consistent results batch to batch — the ratio is fixed, so your only variables are water and technique
  • Less time at the bench — no weighing bran, no sourcing gypsum, no mixing three separate ingredients
  • An easy route to turkey tail too — cut it 50/50 with plain hardwood pellets and you’re at the right bran level

Why supplement hardwood at all: Wood is mostly carbon. In nature, wood-decomposing fungi take months or years to extract enough nitrogen from a log to fruit. Adding bran shortcuts that — it supplies readily available nitrogen, sugars and minerals, so the mycelium builds biomass faster and has more stored energy when it’s time to fruit. That’s why supplemented sawdust blocks outyield plain sawdust for species like shiitake and reishi.

Why more isn’t always better: The same nutrients that feed your mycelium also feed bacteria and moulds. Every step up in bran makes the substrate richer for competitors as well, which is why supplemented sawdust must be fully sterilised, and why each species has a sweet spot. 20% suits shiitake and reishi. Turkey tail is adapted to leaner wood and does best at around 10% — higher than that adds contamination risk without much benefit.

How to prepare your substrate

Hydrate → bag → sterilise → cool → inoculate

Hydration ratios — 80/20 hardwood & bran
Dry mix Water to add Wet substrate yield Fills approx.
900 g 1,300 mL (1.3 L) ~2.2 KG One 2.2 KG grow bag
1 KG 1,400 mL (1.4 L) ~2.4 KG One large grow bag
2 KG 2,800 mL (2.8 L) ~4.8 KG Two large grow bags
5 KG 7,000 mL (7 L) ~12 KG Five large grow bags

Target field capacity: ~60% moisture. Bran holds water differently to pure hardwood, so treat these ratios as a starting point and always confirm with the squeeze test.

Preparation steps
1. Weigh your dry mix into a clean tub or directly into your grow bag. For turkey tail, combine equal parts mix and plain hardwood pellets first (see species guide below).
2. Add hot water at the ratios above. The pellets break down within a few minutes. Mix thoroughly so the bran and gypsum stay evenly distributed — don’t let dry pockets form at the bottom.
3. Check field capacity: squeeze a handful firmly — only a few drops should fall. If water streams out, it’s too wet; add a little more dry mix. Over-wet bran substrate is the most common cause of bacterial contamination, so err slightly on the dry side.
4. Load into filter patch grow bags, fold the tops loosely and sterilise by pressure cooker or steam (see below). Allow to cool completely to room temperature — ideally overnight — before inoculating.
5. Inoculate with grain spawn in your still air box or in front of a flow hood, then heat-seal or tightly fold and tape the bag and mix the spawn through.
Sterilisation — two ways to do it

⚡ Pressure cooking

Pressure cooker or autoclave at 15 PSI — 90–120 minutes

The most reliable option for home growers. Time the run from when the cooker reaches full pressure, use the longer end of the range for bigger bags or full loads, and let the cooker depressurise naturally rather than venting it.

♨️ Steam sterilisation

Steam at 90°C — at least 60 minutes

Ideal for larger batches that won’t fit in a pressure cooker — a steam drum, steam box or barrel steamer all work. The 60 minutes starts once the centre of the bags reaches 90°C, not when the steam starts, so allow extra warm-up time for full loads.

Don’t skip the heat treatment. Bran makes this a nutrient-rich substrate, and an untreated or under-treated bag will feed bacteria and mould as readily as your mycelium. Whichever method you use, let bags cool completely before inoculating.

Which mushrooms this mix is made for

Three wood-loving species that reward a supplemented hardwood block.

Species How to use the mix Grower notes
Shiitake (Lentinula edodes) ✅ Use as-is — 20% bran A slow, patient colonisation. Blocks typically go through a “popcorning” stage, then develop a brown skin before they’re ready to fruit. A cold soak or temperature drop helps trigger pinning.
Reishi (Ganoderma lucidum) ✅ Use as-is — 20% bran Produces long antlers in high CO₂ and classic shelf-like conks with more fresh air — steer the shape with your ventilation. Expect a slower crop measured in weeks, not days.
Turkey Tail (Trametes versicolor) ⚠️ Dilute 50/50 with plain hardwood pellets — 10% bran max Turkey tail prefers a leaner substrate. Mixing equal weights of this blend and plain hardwood pellets brings bran down to 10%. Going above 10% raises contamination risk without much gain.

Mixing ratios at a glance

Blend Recipe Final bran / gypsum Best for
Straight mix 100% Hardwood & Bran Mix + water 20% bran · 5% gypsum Shiitake, reishi
Turkey tail blend 500 g mix + 500 g hardwood pellets per KG 10% bran · 2.5% gypsum Turkey tail

Growing oysters, chestnut or pioppino? Those species do better on our Masters Mix Pellets — a hardwood and soy hull blend built for fast, heavy-fruiting species.

♻️ Don’t throw away your spent blocks

Once your blocks have finished fruiting, they’re far from waste. Partly digested hardwood and bran makes an excellent compost ingredient — the mycelium has already started breaking down the lignin and cellulose, so soil organisms can get to work faster than on fresh woodchip. Crumble spent blocks into the compost heap, use them as a moisture-holding mulch around trees and shrubs, or dig them into garden beds to improve structure. A closed loop from grow room to garden.

Storage
Store sealed, in a cool, dry place out of direct sun. Hardwood pellets absorb humidity and will start to break apart if left exposed, and bran is a natural food product that can attract pantry pests and lose freshness over time. Keep the bag closed between uses, keep it off concrete floors where moisture can wick through, and for best results use within a few months of purchase.
🐾 Keep away from pets and livestock. This is a cultivation substrate, not animal feed or food — store it where dogs, chooks and other animals can’t get into the bag.
How much do you need?
Quantity Wet substrate yield Best for
1 × 1 KG bag ~2.4 KG wet A single block · trying shiitake or reishi for the first time · testing a new strain
2 × 1 KG bags ~4.8 KG wet A small run of blocks · turkey tail growers mixing 50/50 with hardwood pellets · regular hobby growing
5 × 1 KG bags ~12 KG wet Full pressure cooker or steam loads · serious hobbyists and small commercial growers · lowest per-KG cost

Sold in 1 KG bags — buy 2 or 5 bags and the multi-bag discount applies.

Ingredients
Australian hardwood pellets (100% Tasmanian Oak) 80%, organic wheat bran 20%, gypsum (calcium sulphate) added at 5% of dry weight.
The Kai Kai Farm story

Kai Kai Farm is a family operation run on Tamborine Mountain in Queensland’s Scenic Rim. We grow gourmet mushrooms commercially and supply the growing community with the same substrates, bags and inputs we use in our own production.

Shiitake and reishi taught us that plain hardwood only gets you so far. We settled on this 80/20 hardwood and bran blend with gypsum after running it through our own sterilisation and fruiting rooms, and it’s now the base we use for those species ourselves. Pre-blending it saves you the fiddly part and takes the guesswork out of the ratios.

Whether you’re running a single bag in a stovetop pressure cooker or a full steam drum, this is the mix we’d hand you for shiitake and reishi. It’s the mix we use.

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