Mushroom Substrate

Mushroom Substrate

Mushroom substrate is the material mycelium grows through and fruits from. Get it right and a grow runs itself. Get it wrong — too wet, wrong pH, not sterile — and you lose weeks to contamination before you see a single pin.

Everything on this page is what we sell and what we grow on ourselves: substrate that arrives already hydrated to field capacity, pH-buffered and either sterilized or pasteurized, in sizes from a single 1 lb test bag to 25 lb bulk.

Shop all mushroom substrate · Work out how much you need

The four substrate types

Manure-based substrate

Composted manure is the standard for Agaricus species — white button, cremini and portobello — and it works well for dung-loving species generally. It carries more nitrogen than straw or wood, which is what those species want.

Available as 1 lb, 5 lb and 25 lb bulk. There's also a horse manure and straw blend if you want something a little lighter in texture.

Growing button or portobello? You also need a casing layer. Agaricus will not pin without one — this is the single most common reason a button grow colonises beautifully and then does nothing.

Straw substrate

Pasteurized straw is the cheapest and fastest route to fruiting for oyster mushrooms and wine caps. Colonisation is quick, the material is forgiving, and biological efficiency is lower than hardwood but the turnaround is faster.

Our pasteurized straw comes in 5 lb bags, already chopped, hydrated and heat-treated.

Hardwood substrate

Supplemented hardwood sawdust is what the wood-loving species want: lion's mane, shiitake, reishi, maitake, chestnut and enoki. Slower to colonise than straw, but yields are higher and flushes keep coming.

Available in 5 lb and 25 lb bulk.

Grain spawn

Grain isn't a fruiting substrate — it's the carrier. You colonise grain first, then use it to inoculate a bulk substrate. Rye, popcorn, milo, millet and oats all work; the differences are mostly about kernel size and how easily the spawn breaks up when you shake the bag.

We sterilise every grain product under pressure before it ships, so it arrives ready to inoculate. Browse grain bags and grain jars, or go straight to rye berry, popcorn or multi-grain.

Which substrate for which mushroom

Species Spawn on Fruit on Notes
Oyster (Pleurotus) Any grain Straw, hardwood or coir The generalist. Straw is faster, hardwood yields more. See our full oyster substrate guide.
White button & cremini Rye or millet Manure compost Requires casing soil
Portobello Rye or millet Manure compost Same as button — casing required
Lion's mane Any grain Supplemented hardwood Recipe and ratios
Shiitake Any grain Hardwood sawdust blocks Long colonisation, browning phase before fruiting
Reishi Any grain Supplemented hardwood Reishi substrate recipe
Enoki Any grain Sawdust with bran Cold fruiting conditions
Wine cap Any grain Straw or wood chips Outdoor beds

Make it or buy it

Making your own substrate is genuinely worth learning, and we publish the recipes for free — there's no catch. What people underestimate is the equipment and the failure rate, not the ingredients.

Making it yourself costs you: a pressure canner or steriliser large enough to matter, several hours per batch, somewhere clean to work, and a contamination rate that's high while you're learning. Bulk ingredients are cheap. The time and the failed bags are not.

Buying it costs you more per pound and gets you substrate that's already at field capacity, already pH-buffered, and already sterile in a sealed bag. For most growers the honest comparison isn't price per pound — it's whether you'd rather spend a Saturday running a pressure canner or spend it inoculating.

If you want to make your own, start here: manure substrate recipe, simple substrate recipes, rye berry grain spawn.

Sterilized or pasteurized?

Both kill competitors. They're not interchangeable.

Sterilization means pressure and heat above 250°F, which kills everything including spores. Grain must be sterilized — it's nutritious enough that anything surviving will outrun your mycelium. Every grain product we ship is pressure sterilized.

Pasteurization runs cooler, around 160–180°F, and leaves beneficial organisms alive. That's what you want for straw and manure, where a living microbial community actually helps suppress the things you don't want.

More detail: signs your substrate is contaminated and how to prevent mould.

Moisture, pH and the things that quietly ruin grows

Field capacity is the target: squeeze a handful hard and you should get a few drops, not a stream and not nothing. It's the single hardest thing to hit consistently by hand, and the most common reason a batch fails. Ours ships at field capacity. If you're mixing your own, read optimising water content and how to measure moisture.

pH wants to sit around 6.0–7.5 for most species. Gypsum and lime are how you get there and hold it. Why pH matters.

Supplementation raises yield and raises contamination risk at the same time. Adding nutrients to substrate.

How much do you need?

Work it out before you order — running short mid-grow is worse than over-ordering. Our mushroom substrate calculator takes your container size and count and gives you a number. There's also a walkthrough on calculating the right amount for your grow.

Shop by format

Free shipping on orders over $150.

Common questions

What is the best all-round mushroom substrate?

There isn't one, and anyone who says otherwise is selling a single product. Match the substrate to the species: manure for Agaricus, straw for oyster and wine cap, hardwood for lion's mane, shiitake and reishi. Grain is for spawn, never for fruiting.

Can I reuse mushroom substrate?

Sometimes, with caveats. Full answer here.

How long does substrate keep?

Sealed and sterile, several months. Once opened, use it. Shelf life detail, and how to store what you don't use.

My substrate colonised but nothing is fruiting. Why?

Usually fruiting conditions rather than the substrate — or, for button and portobello, a missing casing layer. Troubleshooting guide.