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Mushrooms and other cultivated fungi

by  Maggy Wassilieff

Button mushrooms were the focus of New Zealand’s mushroom industry for nearly 50 years. Today a range of edible fungi are grown, including shiitake and oyster mushrooms, and truffles – one of the world’s most expensive foods.


Mushroom industry

Cultivation in New Zealand

Commercial mushroom cultivation in New Zealand began in the 1930s when the Brightwell brothers of Avondale, Auckland, imported button mushroom (Agaricus bisporus) spawn from Britain and grew them in a heated shed. By today’s standards their methods were fairly haphazard.

In the 1960s, cultivating and sterilising techniques had been refined enough to provide reliable yields, and a mushroom industry began to develop. Until then, most New Zealanders could only eat mushrooms for a brief period each year, when field and horse mushrooms (Agaricus campestris and A. arvensis) appeared in paddocks after the first autumn rains.

Annual production in 2007 was about 7,500 tonnes, most of which was consumed fresh within New Zealand. A small amount was canned, and some was exported fresh to Asia and Australia. The industry was dominated by two large growers, who supplied the major supermarkets. Compared to the productivity levels (weight of crop produced per area) of European and North American growers, New Zealand’s productivity was low.

Cultivating mushrooms

There are three main stages of mushroom cultivation:

  • preparing mushroom spawn
  • preparing a growing medium (compost)
  • growing mushrooms on compost.

These stages are quite separate. They require different facilities, and are often done by different companies.

Mushroom spawn

A small piece of mushroom is grown in tissue culture, where it spreads by fine filaments called mycelia. Sterilised cereal-grain seeds such as rye, wheat or millet are inoculated with pieces of mycelia. This spawn is then used to introduce the mushroom fungus to the compost on which it will grow.

Compost

Button mushrooms need a food source, which must be decomposed. In New Zealand, mushroom farmers make their own compost from a mix of moist wheat or barley straw, chicken and/or horse manure, and gypsum (calcium sulfate).

The mix is allowed to compost for three weeks, during which time it is regularly turned to aerate it.

Mutant mushrooms

The different mushrooms on sale – white buttons, Swiss browns or crimini, and Portobello flats – are different strains of the same species. In nature, Agaricus bisporus mushrooms have brown caps – the white-capped variety is a mutant type that was selected for cultivation.

Growing mushrooms

When the compost is ready, it is loaded into growing containers (wooden trays, growing shelves or plastic bags) and pasteurised at 60°C to kill any pests. Mushroom spawn is then mixed through and left for two to three weeks to grow and completely colonise the compost. A damp casing of peat, lime and bentonite is then placed over the mixture, and helps stop it drying out. The temperature, humidity and carbon dioxide levels in the growing rooms are adjusted to stimulate the spawn to form reproductive structures (button mushrooms).

Mushrooms first appear on the compost surface 15–21 days later. They grow in a series of flushes, about three to five days apart. Two to four flushes are hand-harvested from each container. By picking mushrooms at different stages of maturity, growers get buttons with unopened caps, cups with open caps showing the gills underneath, and flats with large expanded caps and showy gills.


Specialty mushrooms

New Zealand has a small specialty-mushroom industry that has developed since the mid-1980s. Countries in Asia and mainland Europe have long traditions of eating a variety of fungi, but New Zealand does not. Few fungi were eaten by Māori, usually only when other food was scarce. The first Europeans who settled in New Zealand were mainly from Great Britain, and simply gathered wild field mushrooms in season.

In the early 2000s, New Zealanders were increasingly exposed to a range of edible fungi, brought in by new Asian immigrants, or eaten in international cuisines.

Wood ear fungus

The first commercial sale of edible fungi in New Zealand was in the 1870s, when Taranaki merchant Chew Chong sent bags of dried wood-ear fungus (Auricularia cornea) to his homeland, China. The fungus was in demand for the crunchy, chewy texture it added to food.

Wood ear fungus grows naturally on dead trees in lowland forest. Tonnes were harvested as settlers cleared forest for farming, and exports to China continued until the 1950s. In the 2000s, the fungus is now mostly imported to New Zealand from China, in dry form. Taiwanese growers had started cultivating a closely related fungus on sawdust blocks in the 1960s, and it became uneconomic to harvest it in the wild. A small quantity is now grown in New Zealand for the domestic market.

Wood food

Wood ear fungus has a very mild flavour and is added to soups, stir-fries and stews for its chewy texture and visual appeal. The dried fungus is soaked in warm water for 20–30 minutes until soft, then cut into strips and lightly cooked.

Shiitake

In New Zealand, shiitake (Lentinula edodes) mushrooms are cultivated on specially prepared bags of sterilised sawdust and bran. The first shiitake farm started in Auckland in 1985. It was a large-scale operation, exporting up to 7 tonnes of fresh mushrooms a week to Asian markets, but failed two years later when its parent company collapsed. Since then a few smaller shiitake farms have started up, supplying local restaurants and supermarkets. Fresh shiitake have a meaty texture, and are used in stir-fries and soups. Shiitake is not found naturally in New Zealand, but a closely related edible species, Lentinula novaezelandiae, sometimes grows on fallen logs in native forest.

Oyster and phoenix mushrooms

Cultivation of oyster mushrooms (Pleurotus ostreatus) and phoenix mushrooms (P. pulmonarius) began in New Zealand in 1994. Previously, quarantine restrictions prevented people from importing spawn. Oyster mushrooms are raised on bags of pasteurised straw, and phoenix mushrooms on sawdust blocks. Although these large fan-shaped fungi are relatively easy to grow, production levels are low, as few people in New Zealand know how to cook them. They are mild-tasting, and readily absorb other flavours.

Enokitake and white jelly fungus

In the early 2000s, small quantities of enokitake (Flammulina velutipes) and white jelly fungus (Tremella fuciformis) were cultivated, mainly for Asian consumers. Both species can be grown on sawdust blocks. The white jelly fungus must be grown with a companion fungus, which degrades sawdust chemicals into forms that it can absorb. Enokitake mushrooms are added to Japanese soups; jelly fungus is often eaten as a syrupy dessert.


Truffles and other ectomycorrhizal fungi

Ectomycorrhizal fungi live in a symbiotic (mutually beneficial) relationship with the roots of certain living trees. Unlike other commercially cultivated fungi, they cannot be grown on dead materials. There are a number of edible species, including porcini (Boletus edulis), matsutake (Tricholoma matsutake) and truffles (Tuber species). These are all native to the northern hemisphere, where they are only available fresh during short growing seasons in the autumn and winter.

Truffles

Truffles – the most expensive foods in the world – are the reproductive structures of Tuber species. They are produced underground and emit a distinctive smell when ripe with spores. Périgord black truffles (Tuber melanosporum) are considered delicacies for their distinctive earthy, musky flavour, which is imparted to food by even a tiny sliver.

Truffles in New Zealand

Since the mid-1980s, truffles have been the focus of a small group of New Zealand researchers and growers. The first truffles grown in the southern hemisphere resulted from experimental work by Ian Hall of Crop & Food Research. Using techniques developed by French and Italian scientists, he infected oak and hazel tree seedlings with Périgord truffle mycelia. In 1987 and 1988 they were planted in a number of places around New Zealand, and in 1993 a few small truffles were harvested near Gisborne.

By 2007 New Zealand had over 100 truffières (truffle plantations), ranging in size from a few dozen to many thousands of trees. Nine plantations had produced truffles, and at least one harvested more than 40 kilograms of truffles per hectare annually. The domestic market accounted for the entire crop, which was worth around $3,500 per kilogram.

Other truffles – the bianchetto (T. borchi) and the burgundy (T. uncinatum) – have been grown successfully in New Zealand. Although not as highly regarded as Périgord truffles, they still sell for a good price.

Fungal futures

There is potential to increase New Zealand’s export trade of fresh mushrooms to Asian markets if productivity can be raised. New Zealand’s extensive areas of managed pine forests could support crops of edible ectomycorrhizal fungi. To this end, scientists are investigating whether they can cultivate shoro (Rhizopogon rubescens) and matsutake (Tricholoma matsutake). A few other ectomycorrhizal fungi are promising candidates for cultivation, but New Zealand has strict import restrictions on many edible fungi species.


External links and sources

More suggestions and sources


How to cite this page: Maggy Wassilieff, 'Mushrooms and other cultivated fungi', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/mushrooms-and-other-cultivated-fungi/print (accessed 18 November 2017)

Story by Maggy Wassilieff, published 24 Nov 2008