Capel Mushrooms was established in 1962 and is now run by the founder’s sons, Damian and Patrick Hearne. In 1988, faced with the problems of being a relatively small mushroom grower in an increasingly competitive market, Damian and Patrick took the decision to become organic, having dismissed alternatives such as moving into snail farming or rhubarb growing. As one of the first organic mushroom growers in the country, they then faced new problems, not least the lack of a market. However, they persevered and developed a solid reputation as organic growers.
At the main site in Capel St Mary, the compost on which the mushrooms grow is produced and used to cultivate closed cap mushrooms. Compost is also produced for a second site at Trimley, where they grow open cap, brown cap, portobello and portobellini mushrooms. All these mushrooms are, in fact, the same species, Agaricus Bisporus, but different strains and growing times allow the variations. Capel work as part of a co-operative with another organic grower, Gourmet Mushrooms, who produce speciality mushrooms such as Pleurotus (similar to Oyster) and Shii-take.
Agaricus Bisporus is a secondary decomposer that grows on already partially decomposed material, the compost. The first stage in cultivation is to produce the compost from organic wheat or triticale straw and chicken manure. The straw is wetted and mixed with the manure before being left to compost, initially in the open but then in a partly enclosed heap with air introduced from beneath. The process is partly microbial and partly chemical with temperatures in the heap reaching 80°c. After a total of three weeks, the compost enters a closed system for a week, where the ammonia levels are brought down.
The compost is now ready for growing. Grains innoculated with spawn are introduced and the compost blocked up and placed on racks of four tiers. In rooms with carefully monitored and controlled temperature and CO2 levels, the spawn is encouraged to run, the fungus feeding on the compost and the mycelium threads growing throughout. After a little over 2 weeks, a casing of peat is placed on top of the compost. Without the casing, the fungus will never produce fruiting bodies, the mushrooms. Through the introduction of more air, the conditions are changed to encourage “pinning”, the forming of mycelial nodules that will become the mushrooms. It’s important that this occurs on the surface of the casing so the mushrooms don’t grow through it and emerge dirty.
The racks are now transferred to the growing rooms, where up to 3 flushes will be produced at weekly intervals. The mushrooms are picked and cut by hand and despatched to customers. By restricting production to closed cup mushrooms at the Capel site, Damian and Patrick are able to limit the number of stray spores that would otherwise get into the compost and disrupt the carefully controlled stages.
Being organic, there are few controls that can be used in case of attack by disease or other fungi. Often the best remedy is to sacrifice the entire room’s crop and sterilise it to prevent spread to other parts of the farm. Small outbreaks can be treated with salt. The small scale of the operation lends itself well to organic methods.
The mushrooms that result are of the highest quality and supplied as fresh as possible to Capel’s wholesale customers and so the consumer. The farm is capable of producing up to 30,000 lb a week, depending on demand and success rates. Besides the mushrooms, the spent compost is a valuable output, used by gardeners and organic farmers as a useful source of fertility.