For peat's sake
Why you need to get peat out of your mushroom grow
If you’re a mushroom grower, you’ve no doubt heard of—or have actually used—peat in your grow operation. Peat forms naturally from dead plants that grow in special environments called peat bogs. When left long enough to become crushed under layers of rock over millions of years, peat ultimately becomes coal. As a result, peat bogs, covering around 3% of the planet’s surface, are responsible for storing around 15–30% of the planet's carbon. Peat accumulates very slowly, around 0.5–0.6 mm a year, so it can take a very long time to recover once dug up. Given the serious issue of climate change, some countries like the UK are planning to ban the sale of peat-based compost over the next few years.
So how did peat become so popular in the home mushroom-growing community? Much like plastic, peat has properties that make it very useful to mushroom growers, in this case as a casing layer for fully colonized substrates to push their mushrooms through. Peat holds water incredibly well (though not as well as vermiculite) and is low in pH, so it resists contamination naturally. Peat is used extensively in the commercial mushroom-growing industry, which is probably why early mycology writers promoted its use for home mushroom growers as well.
While peat can be avoided in most methods of home mushroom cultivation, some grow projects will never require you to even think about using it. PF Tek is a good beginner-friendly method that will keep you in mushrooms without the use of peat, as will growing sclerotia or wood-loving Psilocybes (the latter can be cased with regular soil).
We minimize our use of peat wherever we can, either by avoiding casing layers altogether or using peat-free alternatives when we need to. Although many growers seem obsessed with maximizing yield, we try to impress on folks that the benefits brought by peat-based casing are likely marginal, especially when compared to just inoculating more substrate. Making up an extra monotub will get you far more mushrooms in total than fewer tubs cased with peat, providing you follow all other steps in this book correctly—so we’d like to challenge you, home grower, to avoid peat-based casings, or casings altogether, when possible.
We’ve only got one planet—so let’s look after it.
This post is an extract from the expanded and updated second edition of best-selling The Psilocybin Mushroom Bible, released by Green Candy Press in May 2024. You can order the new edition by clicking here: