A casing layer provide a moist porus structure for the primordia of the particular species of fungi to develop. It is a way of imitating an ideal soil structure. Some mushrooms, such as the Stropharia Ruguso-annulata require a microbial casing layer. Grown outdoors this will develop naturally but poses challenges for artificial cultivation. Other species can be grown on a substrate such as rye grain then when fully colonised a casing layer is added whether the substrate is in a tray or jar. The mycelium will then colonise the casing layer in preparation for fruiting from the the surface.
- 10 parts peat
- 10 parts vermiculite
- 1 part CACo3 (Limestone)
- 1 part CASO4 2H2O (Gypsum)
- mix peat, CASO4 and CACo3
- add water slowly while mixing
- add vermiculite and continue to add water
- test for field capacity
- Mix the peat, limestone and gypsum and then slowly mix in the water until moist
- add the vermiculite and continue to add water until you reach the require “field capacity”
- Field capacity is a level of moisture before saturation, the maximum water content before it would be considered water logged. Too much water whether in your substrate or in a casing layer will create an anaerobic environment and increase the risk of contaminants. It’s hard to describe but basically, squeeze a handful of the casing layer it a “rivulet” or quick stream of water should come out for 1 to 2 seconds before reduced to just a few drops.
- Now put the casing mix into jars, lids on but not tight, cover with tinfoil and sterilise in a pressure cooker at 15psi for at least 30mins.
- Leave to cool for 6-8 hours, now the casing can be added to the layer of substrate in whatever cropping container you are using.