There’s really no excuse for not growing mushrooms if you have a garden. As well as producing a delicious crop, mushroom mulches (the layers of material in which fungi grow) keep down weeds, retain moisture and help build the soil to grow healthy plants.

A good species to start with is the garden giant, also known as the wine cap or king stropharia. These are big, meaty mushrooms, delicious in stews, easy to culture and quick to grow (make sure to pick them before they get too big and lose their flavour).

Start in March or April to avoid the risk of frost. Choose a semi-shaded spot, ideally among fruit bushes or trees, which will benefit from the mulch. Get your hands on mushroom spawn. Spawn is a substance, usually grain, that’s been treated with the fungal culture or mycelium you need to grow mushrooms. We sell it but it is available from farms or grow-kit shops.

For the substrate, source two or three large cardboard boxes stripped of plastic and without too much ink; a couple of wheelbarrows of fresh woodchip (not more than a month old) containing more hardwood than softwood (call your local tree surgeons or landscape gardeners and ask if they have any); and a 1kg bag of straw, which you can get from a pet shop.

For 1.5kg of mushroom spawn, prepare an area of 1-2m2 for the bed. Dig out any persistent weeds. Cover the ground with a sheet layer of cardboard and saturate with water, piercing holes in the cardboard where water is pooling. Cast a third of the spawn over the surface, making occasional small islands, then cover evenly with 3cm depth of woodchip and water lightly.

Create a second layer of cardboard, using smaller, torn-up strips, and thoroughly saturate. As before, cast the spawn and cover with 3cm of woodchip.

Repeat the process to create a third layer. Finally, cover the bed with a layer of straw and water it once more thoroughly. Water every day for the first week, then every other day for the next three weeks, and once a month thereafter – unless there is enough rain.

After four to eight months, the mycelium should have grown through the woodchip. Keep an eye on the bed when fruiting conditions are good – at temperatures of 14-18C, often when sunshine has followed rain. The mushrooms will be ready to pick after 48 hours of appearing. (Be sure to properly identify your garden giant mushroom: it should have a thick white stem, a burgundy to brown cap, greyish gills and black spores.)

After two harvests, add a 5-10cm layer of woodchip before winter and cover with straw. You can do this for two-three years, after which it is best to make a new bed. You can easily propagate more beds by taking the myceliated woodchip from your original as your “spawn”. Or expand your horizons and try growing a different mushroom, such as oyster or wood blewits.

Garden Giant Grow Kit

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