Oyster (Pleurotus ostreatus) – Commonly sold and easy to cultivate it’s a familiar mushroom to the beginner home grower experimenting with “grow kits”. A voracious species it has the potential to produce a huge array of enzymes and decompose a wide range of cellulose and lignin-based substrates. It can be grown on logs, as you will know if you have had an experience foraging for mushrooms as it likely that you will find Pleurotus ostreatus or related species in your locality. However, it is most commonly grown on cereal straw.
Cereal straw is readily available, inexpensive and easy to obtain. As a substrate it needs to be chopped and pasteurised. It is possible to purchase pre-chopped straw otherwise a garden shredder can be used, or a garden strimmer and a large barrel or other plastic container. Pasteurisation is usually achieved through submersion in hot water (74c). However, the objective of removing competitor micro-organisms can be achieved through a lime treatment, creating an alkaline solution to submerge the substrate for up to 12hr. At the scale we are proposeing for this scheme, we will be using net bags and 200l plastic barrels to submerge the straw in a soultion of 120l of water and approximately 45g of CaHo2 (calcium hydroxide). Once processed the waste water can be neutralised with citric acid.
Once fully drained the spawn is either mixed en masse in a clean container then added to cropping containers or layered with the straw in the clean 25l bucketswith pre-drilled holes for the fruitbodies to grow from. These are then left to incubate for 2-4weeks depending on the incubation temperature.
The buckets can be stacked in a growing enviroument that regulates humidity, fresh air exchange and provides a minimum level of lighting. Ideally temperature is also controlled but will often result in significant extra costs. This can be avoid to some extent with versatile species such as those in the Pleurotus complex, and the many strains now available with different and wide ranging fruiting temperatures. In short, with an insulated grwoing environment and the use of suitable strains the need for temperature control in unecessary with, however, some loss in efficiency. Once placed in the growing environment initiation or “pinning” should occur within 5 days with another 5-10 days until harvest.
We are modelling a growing scheme with a predictable target of 10kg of fresh mushrooms per week. Using the 25l buckets with two flushes over of period of 5-6 weeks this means preparing and subsequently initiating 6x buckets per week. This could be increased with 3rd and 4th flushes from the substrate although there is an increased risk of contamination. To concounter this subsequent flushes can be produced in an outdoor covered area where a similar level of humidity and frsh air exchange can be replicated.
The fruitbodies are simply removed from the base of the short stem attched to the substrate. Any residual substrate is cleaned from the fruitbody whic can then be placed in a plastic mushroom tray for transport. They can be rrefridgerated to increase shelf otherwise best consumed within 3 days. Drying excess is also an option with Oyster mushrooms.
Although it is possbile to continue propagting Pleuotus species using the cardboard spawn method it is unsuitable for this scale of production. The most cost effect way of inoculating straw substrates is to use sawdust spawn. This requires the capacity to use grain spawn to innoculate sterilised sawdust although the useof wood pellets is also an option.