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Growing commercial mushrooms in Dunsandel
Edible mushrooms, available in a plethora of funky shapes and a variety of strains, are a superfood that is increasing in popularity, with the mushroom market expected to grow by 9.5 per cent worldwide this year alone. Recognised for their nutritional benefits as well as for the unique taste and texture they add to dishes, high-yield mushrooms such as the White Buttons or Swiss Browns are
commercially farmed to meet the ever-growing demand.
While in nature, mushrooms seem to pop up overnight almost magically, cultivating mushrooms commercially is a much more complex endeavour, where mushrooms are spawned in a very specific straw compost mix in large trays, shelves or bags in temperature-controlled sheds.
Around 2300 varieties are classed as ‘edible’, dependent on whether they have a favourable taste and aroma, and whether they are ‘safe’ – that is, lacking the poisonous toxins contained in some forms of fungi. The most common commercial variety, White Button mushrooms, known as Agaricus bisporus, are the strain grown at Greendale Mushrooms, a Dunsandel
mushroom farm owned by George Gibb and his wife Vivian.
Mushroom growing is a somewhat delicate process, and a completely different farming experience to that of George’s childhood, where he grew up on a sheep farm in North Canterbury, a transition that required more than a little adjustment. ‘It was difficult,’ says George. ‘I had some things go wrong that were not really my fault, but it took me too long to work out what they were, even with expert help, so this made the first 12 months incredibly difficult.’
Those initial issues (predominantly around faulty straw) were ironed out, and Greendale Mushrooms, while a
comparatively small-scale operation, has since had consistent high yields, with the farm producing around 2–3 tonnes of mushrooms per week, equating to an average of around
140 boxes per day which are sold to wholesale markets in Christchurch, Dunedin and Invercargill.
George grows the mushrooms in trays in a pasteurised compost mix made onsite from a mix of straw and chicken litter, which is then encased in peat, a common system that was set up by the farm’s previous owners. Mushrooms appear around two weeks after ‘spawning’, a process where wheat grains impregnated with mushroom spawn are seeded through the compost, which then form mycelium, a fibrous white web-like collection of mushroom cells which grow in the compost in the dark, temperature-controlled sheds. The process is ecologically sustainable by default, utilising waste products (such as the chicken litter and wheat straw), which can then be reused again as compost for gardeners.
‘Mushrooms are ideally suited to fulfil the needs of some of the big challenges facing the world population, and this extends to New Zealand,’ says George. ‘They are environmentally friendly and can be produced in very intensive systems using very little chemicals.’The farm employs 12 staff, with mushrooms being hand-picked as this is still considered to be the most reliable method of harvesting the fragile fungi. ‘We take four crops from one batch of compost before it is spent,’ says George. ‘Then people use it for their gardens which it is absolutely ideal for.’
While not particularly high in protein, mushrooms still provide a viable alternative to a meat-based meal. ‘They are very healthy as a food, they are not primarily carbohydrate,’ says George. ‘Their texture and taste make them ideal to be used to replace, in part or in whole, some less environmentally friendly or healthy foods. You can still have a traditional everyday dish such as Spaghetti Bolognese, but if you substitute some mince for some chopped mushroom the dish instantly becomes healthier, better for the environment, and unless you have an aversion to mushrooms, you haven’t destroyed the character of the dish.’
Mushrooms are low in fat, and therefore calories, while being high in essential trace elements such as potassium, selenium, folate and B group vitamins. Mushrooms are also versatile: they can be used fresh or frozen, dried or canned, can be eaten raw or cooked and are ‘low waste’ as all parts of the mushroom can be eaten, including the skin and stalk. Even preparation can be minimal depending on the complexity of the recipe, as mushrooms require no peeling and only a quick rinse or wipe down with a paper towel.
While White Buttons are the most common mushroom on the market, other mushrooms such as Swiss Browns, Portobello and White Flats (all versions of the species Agaricus bisporus) are also popular and widely available in supermarkets. Much sought-after Truffle varieties, such as the Périgord (known as ‘Black Gold’), are knobby aromatic mushrooms that grow on the roots of inoculated living trees, and are deemed the most expensive of all fungi, fetching around $3500 per kg as culinary delicacies due to their rarity as they are notoriously tricky to grow, and highly seasonal.
Exotic mushroom varieties, such as Shitake or White
Jelly, are becoming more popular and accessible. ‘In places like New Zealand where our diet has been traditionally pretty
‘Mushrooms are environmentally friendly and can be produced in very intensive systems using very little chemicals.’
repressed,’ George says, ‘people are becoming much more open to trying new tastes and textures, so mushrooms can fulfil this, particularly the more exotic varieties. Exotics are quite different in the way they grow so would need a separate growing facility. There is a limited but growing market for these; in New Zealand this is led by Auckland, but the South Island is starting to catch on. It is something to look at for the future. There are some production problems associated with some varieties, and many varieties seen overseas are illegal to import into New Zealand due to bio-security risk.’
The New Zealand commercial mushroom industry has come a long way since mushrooms were first grown for sale here in the 1930s. With the industry ticking all the boxes – consumers are increasingly demanding ecological sustainability, low environmental impact and high nutritional value from food producers – farms like Greendale Mushrooms look to be well placed for future growth.