Mushroom

Mushroom Compost is the Key to



Growing Mushrooms



The art of making mushroom compost has been developed over more than a century and differs somewhat from that of other forms of compost. In fact, it is likely that the methods of making good quality garden compost were developed out of what was learned making mushroom compost, rather than the reverse.

The French were the pioneers of modern mushroom culture - the first to develop year round production in caves near Paris and the Pasteur Institute was the first to develop cultured mushroom spawn in 1893. Throughout this long history, it has been the methods of making mushroom compost that proved most critical to successful cultivation.


The critical factors in producing good quality mushroom compost are:

1.Very good hygiene to prevent contamination by unwanted microbes

2.The right proportions of manure and straw

3.The use of wheat straw rather than any other kind

4.The generation of sufficient heat to properly pasteurize the compost

5.An adequate supply of Calcium

6.An alkaline pH that reaches neutral (pH 7.0) when composting is complete)


The process begins by soaking the straw in water and then leaving it to drain so that it remains only just moist (only a few drops should come out when squeezing a handful).

Manure and Gypsum are then mixed into the straw and the heap formed up. Only poultry or horse manure should be used (other types will not produce enough heat) and the heap should then heat up quickly.

For every bale of wheat straw, use about eight (8) gallons (36 liters) of dry poultry manure (not litter, but actual manure) or Horse manure. As an alternative to mixing, the heap can be built up in layers of these proportions.

Gypsum is used at the rate of 14 lb (about 6.5 kg) per tonne of manure, so a light sprinkling on each layer should suffice. If the compost looks greasy or sticky when turning, simply add more Gypsum (not Lime).

Ideally, a heap should be six feet high in order to quickly develop enough heat, but a compost bin or tumbler could be used to contain and insulate smaller quantities. The compost should then be thoroughly turned on a weekly basis until it stops re-heating and the pH falls to neutral. At this point it should be used immediately so that only mushroom spawn has the chances to populate it.


The process of growing mushrooms is then simply laying the compost into boxes, inoculating it with spawn and keeping it away from sunlight (a shady area is sufficient) and draughts while the fungus grows. The ideal temperature range is 56-60 degrees F (13-15 degrees C). Lower temperatures will only slow growth, but higher temperatures should be avoided.

Air movement that can dry the compost is harmful, but good ventilation is essential since as little as 2% Carbon Dioxide in the air can harm the developing mushrooms.

Once the fungus has filled the compost and pinheads begin to appear, moistened peat 'casing' is laid over the top and the mushrooms will begin to grow. They are harvested by twisting them out and the holes are re-filled with casing material.

For more detailed information, why not look through our Bookstore for books about Mushroom compost or visit our Organic Composting page.

Mushroom Kits

The easiest way for growing mushrooms, by far, is to buy a prepared mushroom kit. This will contain inoculated compost in a box and a packet of casing material. Usually you just open the box, cover the compost with the casing material and put the whole thing in a cupboard or somewhere else out of the way. You will have mushroom in a couple of weeks and a succession of kits will give you year-round supply.

The problem with kits is that while many are available on the internet, you should find sources in your own country as most quarantine laws will not allow import of such growing material from other countries.

Mushrooms in the Garden

The available information on this tends to be a bit vague, so I will try the various methods suggested and report the results here as I can.

To date, the most likely method would seem to be laying inoculated mushroom compost just beneath a small area of lawn. Some suggest doing so in the vicinity of an apple tree, but I am not sure yet how important this is.

However, I have found one book on the subject. You can find more information about it here (or just hover your mouse pointer over the link text).