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 that 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 any experience foraging for mushrooms as it is likely that you will find Pleurotus ostreatus or related species in your locality. However, commercially it is most commonly grown on cereal straw.
Substrate:
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 with 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 the use of lime (calcium hydroxide), creating an alkaline solution (Ph 12) to submerge the substrate for up to 12 hours. At the scale we are proposeing for this scheme, we will be using net onion bags and 200l plastic barrels to submerge the straw in a soultion of 120l of water and approximately 45g of lime (.4g / litre). Once the straw if processed the waste water can be neutralised with citric acid.
Inoculation:
Once fully drained the spawn is either mixed into the straw en masse in a clean container before being added to a cropping container. Otherwsie the spawn can be layered with the straw. We will be use 25l buckets as the cropping container with pre-drilled holes for the fruitbodies to grow from. These are then left to incubate for 2-4weeks depending on the incubation temperature.
Fruiting:
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 avoided 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 growing 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.
Cropping Cycle:
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 counter this subsequent flushes can be produced in an outdoor covered area where a similar, though less intensive, level of humidity and fresh air exchange can be replicated. A cheap garden polytunnel located somewhere shaded with a sprinkler system is a cheap and easy option.
Harvest:
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 refridgerated to increase shelf life otherwise best consumed within 3 days. Drying excess is always possible with any mushroom.
Propagation:
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 use of wood pellets is also an option.