Editorial photo — our own grow, day 18What you'll need
You can do this with a bucket and a kettle, but four pieces of kit make the difference between a first-time success and a green, mouldy tub. Everything below is what we used for this guide.
Gear for this guide
3 items
Blue Oyster Grain Spawn, 1 kg
Not yet tested
Food-grade 5 L buckets with lids (pack of 3)
Not yet tested
Digital hygrometer & thermometer
Not yet tested
Pick your species
Blue oyster is the most forgiving strain for a first grow and fruits well at UK room temperatures. Pink and golden oysters are faster but prefer it warmer. Oyster species passport →
Prepare the substrate
Mix 2 kg of fresh, used coffee grounds with 500 g of straw pellets. Pasteurise the pellets with boiling water, let the mix cool below 25 °C, then combine with spawn at a 1 : 4 ratio. Not sure about the ratio for your bucket? Use the calculator:
Inoculate
Work in a clean kitchen with washed hands. Layer substrate and spawn into the bucket, press down lightly and close the lid. Drill 12 holes around the sides.
Incubation (days 1–14)
Keep the bucket somewhere dark at room temperature. White mycelium should spread through the mix; our tub was fully colonised in 11 days.
Fruiting & harvest
Once pins appear, humidity needs to stay above 85 %. In a dry UK flat with central heating that means misting 3–4 times a day — or letting a small humidifier do it.
Troubleshooting
Most failed buckets come down to humidity or contamination. See our guides to green mould and no pins after 3 weeks.
FAQ
How long until the first harvest?
About three weeks from inoculation in our grow: 11 days to colonise, then roughly a week to fruit.
Can I use instant coffee?
No — you need fresh, used coffee grounds from brewed coffee.