Grow Mushrooms in 30 Days

Quick, fun and always tasty, I reckon mushrooms are some the most exciting things you can grow! Mushroom-growing kits offer an easy way to get started, but they can be pricey and they aren’t always as reliable as they should be.

So read on or watch our video to discover a deliciously simple way to grow mushrooms in next to no time, and for a lot less…

Mushroom Growing Equipment

I use one gallon (5 litre) lidded plastic buckets as containers for my mushrooms. Mine didn’t cost much, and you may even be able to source them for free – perhaps ask a local restaurant for containers that might have held, for example, pickles. It’s possible to buy special mushroom growing bags, but by drilling your own bucket like this, you’ll be able to reuse it time and again.

You’ll need straw for the mushrooms to grow on, which is widely available and very cheap. And, then, of course, there’s the mushroom spawn itself – I use grain spawn because it’s nice and easy to handle. I like to grow oyster mushrooms – specifically blue oysters – which are the easiest mushrooms you can grow at home, and among the most delicious in my opinion. The mushroom world’s your oyster!

Finally, you’ll need some surgical tape and an old pillowcase or net bag (for instance an onion storage net). Don’t worry, all will become clear shortly…

Prepare Your Mushroom Buckets

Drill a series of holes, half an inch (10-12mm) wide, across the wall of the buckets. Position the first row of holes fairly close to the top of the bucket, with a second row about two-thirds of the way down. Stagger the second row so the holes are not directly below each upper hole. Remove any sharp edges from the holes with sandpaper. The holes not only ensure good air exchange, they’ll also be where the fruiting bodies themselves eventually emerge from.

Drill several smaller holes across the bottom for drainage to prevent excess water from pooling, which could create unpleasant conditions for your fungi.

You could also scale things up by using, say, a five gallon (20 litre) bucket. For something that size I’d suggest up to four staggered rows of holes – up to about 20 holes in total – spaced about six inches (15cm) apart in each direction.

Pasteurising Straw For Growing Mushrooms

I bought my straw from a pet store because it’s clean and, crucially, already comes sliced up into small pieces. This is important, because the smaller the pieces of straw, the quicker the mycelium (the ‘roots’ of the mushroom) will colonise it. You could use a full-sized straw bale instead, but you’ll need to chop it up into smaller pieces first.

To ensure trouble-free growth for your mushrooms, free of any contaminants or weed fungi, you’ll need to pasteurise the straw. This is where that pillowcase or net bag comes in! Stuff it with straw then plunge it into a stockpot or bucket of very hot water.

The water temperature needs to be between 140-175ºF (60-80ºC). You can check the temperature with a jam thermometer. This temperature will kill off most of the microorganisms but leave some of the good guys – the beneficial bacteria – intact, and these will help the mushrooms to grow. It’s important not to put it in boiling water as this would annihilate every single living thing in it, perversely leaving the straw open to infection from contaminants.

Weigh the straw down so it’s completely submerged, and keep it in the hot water for a full hour. Once time’s up, drain off the straw by hanging up the pillowcase or net bag to allow all the excess water to drip off. This will probably take half an hour or so. It’s ready for inoculation once it’s cool to the touch and, when squeezed, barely any water drips out. The wet straw will be quite heavy – at least triple the weight of when it was dry.

Inoculation Time!

Now for the real magic - inoculation time! But first make sure your hands and equipment are squeaky clean, because any contaminants could compete with your mushrooms and spoil everything. Sterilise the bucket and your hands with a solution of isopropyl alcohol, or use some sort of steriliser - powdered steriliser for making homebrew will work.

Massage your bag of grain spawn to separate out all the grains before opening it. Next, layer up the bucket, starting with a few handfuls of your pasteurised straw. Squash it all down, then add a few handfuls of grain spawn. Repeat with more straw followed by a few handfuls of spawn until you reach the top of the bucket. As a rough rule, aim for 5-10% spawn to 90-95% straw. If you have any spawn left over, just seal it up and pop it in the fridge, where it should stay fresh and ready to use for another month or so.

Put the the lid – also sterilised of course – on the bucket. And what about that surgical tape? Good question! Cut off little squares of it and cover all the holes on the walls of your bucket. The surgical tape is breathable and will do two things: it will keep the substrate and spawn protected from unwanted contaminants while still allowing free air exchange, and it will also help retain moisture inside the bucket, keeping up the humidity that fungi love.

Place your bucket on a tray of some kind to prevent any moisture seeping from the drainage holes from causing a mess. Keep it at a comfortable room temperature, and avoid wild swings in temperature. Over the course of the next few weeks the mycelium will spread out from the grain spawn and throughout the straw, ready for the next stage…

Growing Mushrooms in Straw

After two or three weeks, if you peek under the lid you should find that the straw has turned white from the mycelium. Once it has, you’re on the cusp of getting mushrooms!

You should also start to see some ‘pinning’ – the growth of tiny embryonic fruiting bodies of the mushroom – at the holes in the sides of the bucket. But mushrooms don’t grow like plants. Believe it or not, your mushrooms will pretty much double in size every day!

The surgical tape will either drop off as the mushrooms grow, or you can carefully remove it. As your mushrooms grow it’s really important to offer them both light and high humidity. Move them somewhere that gets light but is out of direct sunshine, such as near a window. In the summer this could even be outdoors under the shade of a tree. To keep humidity high, mist your ‘shrooms morning and evening and, if you can, in early afternoon too.

The speed with which the mushrooms grow is the most exciting part as far as I’m concerned! I honestly get giddy with excitement each morning when I check to see how much they’ve grown overnight. Kids will love it too!

Harvesting Your Mushrooms

Harvest your mushrooms when the caps have opened up but before they’ve flattened out. This will also avoid spores going absolutely everywhere and making a mess!

To harvest, just reach behind the clump, twist, and pull free. The holes won’t all crop at the same time, so just take each clump as it’s ready and leave the others to grow on.

You may well get a second crop – or flush – of mushrooms within a few weeks of the first. Just keep that humidity up as before and, all being well, a second and possibly even third flush will be yours for the taking!

Once it’s exhausted you can try using the mycelium-laden straw as ‘seed’ for a fresh batch of pasteurised straw, thereby keeping the cycle going. Break the old batch up into thirds and use it to inoculate three new buckets, layering the mycelium-laced straw with fresh straw in exactly the same way as you did with the grain spawn.