Try an easy home method

Straw in a bucket

The most forgiving of the easy methods. Chopped straw is soaked in limed water, then layered with oyster spawn in a bucket with holes.

How the lime works

Hydrated lime in water makes the water strongly alkaline (a high pH). Most moulds and bacteria cannot live in it, but oyster mushroom mycelium grows fast enough to take over. The straw must soak fully under the water for 16 to 24 hours so every piece is treated. The soak is what protects the straw, so do not skip it or shorten it.

The straw then has to come out of that high pH before it is used. Lift it out, rinse it, and drain it for about an hour. If the straw is still too alkaline, the mushrooms will not grow. Checking the soak water with pH strips or a pH meter (aim for 11 or higher) is better than guessing.

You need

• A clean 20 litre bucket with a lid
• Straw, chopped to 2.5 to 7.5 cm. Wheat straw is the better choice. Barley straw works but gives less.
• Hydrated lime (not agricultural lime, never quicklime), kitchen scales
• Oyster grain spawn, about 1 to 2 kg per bucket
• A drill, gloves, glasses, a dust mask
• Micropore tape

Trade-offs

• Yield: good, with a second smaller flush possible.
• Risk: higher than a kit. Packed or too-warm buckets can go bad inside.
• Needs a bucket, a big soak container and some space.

Steps

1. Drill holes of about 12 mm all round the sides, 10 to 15 cm apart. Wash the bucket and wipe it with a disinfectant spray. Tape over the holes.
2. Weigh 2 g of hydrated lime for each litre of cold water. Wear gloves, glasses and a mask. Stir until cloudy.
3. Put the straw in a mesh bag, push it under the water and weigh it down so it is fully covered. Soak for 16 to 24 hours.
4. Check the soak water with a pH strip or meter. It should read 11 or higher.
5. Lift it out, rinse it with clean water, and drain for about an hour, until a squeeze gives only a few drops. Throw the soak water away. If the straw smells sour or rotten, throw it away too.
6. Right away, layer straw and spawn in the bucket like lasagne, ending with straw. Pack firmly, put the lid on.
7. Keep it warm (18 to 24 °C) and dark for 10 to 21 days until white all through.
8. Peel off the tape, give fresh air and indirect light, and mist the holes twice a day. Small mushrooms appear in about a week.

Used coffee grounds

Fresh grounds from a café or your own machine, mixed with straw and oyster spawn. Very cheap and quick to set up.

You need

• Very fresh used coffee grounds
• Chopped straw, treated as in the bucket method above
• About 500 g oyster grain spawn
• A grow bag with a filter, or a clean 2 litre bag or tub with four 5 mm holes
• A water mister

Trade-offs

• Yield: small to medium.
• Risk: moderate to high. Old grounds, weak spawn or a dried-out mix often fail.

Steps

1. Wash your hands and wipe your bag or tub, tools and work surface before you start.
2. Collect the grounds on the day you start. Grounds on their own pack down tight and let in very little air, so mould gets a head start.
3. Mix the grounds with the treated straw, about half and half by volume. Keep the mix loose and airy, never packed down.
4. Mix in the spawn within 24 hours of collecting the grounds.
5. Fill the bag or tub about two-thirds full and close it.
6. Keep it warm and dark for about 3 weeks, until white all through.
7. Move it to a shaded, airy spot, cut a hole of about 5 cm by 5 cm, and mist twice a day. Do not let it dry out.
8. Pick when the caps start to turn up at the edges, usually 5 to 7 days after small mushrooms appear.

Hardwood pellets

Experimental, with little published evidence. Hardwood pellets swell into loose sawdust when hot water is poured on, which makes a cheap base for wood-loving mushrooms such as oysters.

You need

• Pellets sold for growing mushrooms. Pellets sold as fuel are made for burning: some contain bark, which mushrooms do not feed well on, and you cannot always tell what is in them.
• Boiling water and a heat-safe tub with a lid
• Oyster grain spawn
• A clean bag or tub with air holes

Trade-offs

• Yield: lower than a soy hull and hardwood mix (see the grow bag lesson). Giving the right food is the key to a good crop.
• Risk: higher than a kit. Boiling water is not the same as sterilising.

Steps

1. Wash your hands and wipe your tub, tools and work surface.
2. Pour boiling water over the pellets, about 2 litres per kilogram. They break down into loose sawdust.
3. Put the lid on and let it cool completely. Spawn added while it is warm will die.
4. Mix in the spawn, fill a clean bag or tub, and keep it warm and dark until white all through.
5. Give fresh air and mist, as in the bucket method, and pick when the caps flatten.

Two more easy methods are being written up: a pre-cooked rice pouch and cardboard.

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