The Secret To Growing Straw Mushrooms

Straw mushrooms, or Volvariella volvacea, are cultivated in the warm, tropical climates of East and Southeast Asia. They are often grown on agricultural wastes such as rice straw, but can also be grown on cotton waste, compost piles, grass, leaves, wood chips, and even on termite mounds. Straw mushrooms have been cultivated for thousands of years, with the earliest record of cultivation dating back to the 18th century by Buddhist monks at the Nanhua Temple in China. Today, they are one of the most popular varieties of mushrooms consumed in Asia and are also cultivated on a small scale in the Philippines, Malaysia, Thailand, Vietnam, China, and Eastern Europe. Growing mushrooms on straw is a simple and productive way to cultivate mushrooms at home, and various types of straw can be used, including wheat straw, oat straw, and rice straw.

Straw types: wheat, oat, barley, pea, or rice straw

Straw mushrooms, or Volvariella volvacea, have been cultivated for thousands of years in Asia, with the earliest records of cultivation dating back to the 18th century in China. They are grown on rice straw beds and are cultivated throughout East and Southeast Asia. They are widely consumed and used in Asian cuisine.

When it comes to the types of straw used for growing straw mushrooms, various options are available, including wheat, oat, barley, pea, and rice straw. Wheat straw is commonly used in thatching to create lightweight, waterproof, and well-insulated roofs. It is also used in compostable food packaging and composite lumber production. Oat straw, on the other hand, has a high fibre content and is known to cause digestive issues in horses. Barley straw is another option, but it contains awns that may reduce its palatability. Pea straw is a type of legume straw, which tends to have higher ingestibility than cereal straws like wheat, barley, and oat. Rice straw, the type commonly used for growing straw mushrooms, is an agricultural waste product that can be turned into bioplastic with properties similar to polystyrene.

To grow straw mushrooms successfully, it is essential to prepare the straw properly. The straw should be cut into small pieces, preferably 1 to 3 inches in length, to facilitate mushroom spawn colonisation. While optional, washing the straw with a small amount of dish soap before proceeding to the next step can be beneficial. The specific type of straw used will depend on availability and regional variations, as different straw types are more prevalent in certain areas. For example, in subtropical regions where sugarcane is grown, sugarcane bagasse can be used as an alternative to straw.

Once the straw is prepared, the mushroom spawn can be introduced. Oyster mushrooms are an excellent choice for straw, as they are known to grow well on this substrate. The prepared straw can be placed in bags, buckets, laundry baskets, or spread into a garden bed in a shady area outdoors. Alternatively, a fruiting chamber can be used for indoor cultivation. The fruiting process for mushrooms grown on straw is similar to that of other substrates like sawdust, coffee grounds, or cardboard. By elevating humidity, slightly lowering the temperature, and introducing light, the mushrooms will begin to fruit. Regular misting of the developing mushrooms is crucial to prevent them from drying out.

Pasteurisation: heat or hydrated lime to kill unwanted spores

Pasteurisation is a crucial step in the process of growing mushrooms on straw, specifically targeting the elimination of unwanted spores and harmful microorganisms. This can be achieved through two primary methods: heat pasteurisation and chemical pasteurisation using hydrated lime.

Heat pasteurisation involves the use of very hot water, just below the boiling point. To execute this method, you will need a large, watertight, and heat-resistant vessel. Old bathtubs, clean drums, or stainless steel containers are commonly used for this purpose. The chosen vessel should be packed tightly with straw and then filled with the near-boiling water. This process kills off most unwanted spores and contaminating organisms, creating a more favourable environment for the desired mushroom mycelium to thrive.

On the other hand, chemical pasteurisation employs hydrated lime, also known as calcium hydroxide, which can be easily sourced from hardware stores. This method is often used when pasteurising straw with a substrate. To begin, ensure that your chosen container, such as a barrel or wheelie bin, is clean. Then, simply add hydrated lime to the straw substrate. This process tips the pH balance in favour of the living mycelium while inhibiting the growth of foreign spores, such as mould.

It is important to note that heat pasteurisation does not sterilise the straw, as some hardy bacteria may survive the process. However, these remaining bacteria can sometimes play a beneficial role in protecting the substrate from mould spores and promoting mushroom growth. Additionally, pasteurisation is not always necessary when growing mushrooms on straw, as some growers choose to skip this step.

Overall, by employing either heat or hydrated lime pasteurisation methods, growers can effectively create an environment conducive to the growth of desired mushroom species while minimising the presence of unwanted spores and potential contaminants.

Fruiting: elevate humidity, drop temperature, add light

Straw mushrooms can be grown on wheat straw, oat straw, or rice straw. Sugarcane bagasse can be used as an alternative if you live in a subtropical area. It is important to ensure that the straw is in good condition, with no signs of mould or rotting.

Once you have prepared the straw, you will need to create the right conditions for fruiting: elevate humidity, drop the temperature, and add light.

Elevate Humidity

Humidity is an essential factor in mushroom cultivation. Mushrooms require high humidity levels to start the formation of primordia, which are small bumps that eventually grow into mature mushrooms. Throughout development, mushrooms need humidity to grow to maturity. Poor humidity levels can cause mushrooms to stop growing, discolour, and form cracks. Therefore, it is important to maintain the ideal humidity level for growing mushrooms. This can be done by misting the mushrooms regularly with a spray bottle, using pond misters, fans, perlite, and companion planting. A humidity sensor can help monitor humidity levels.

Drop Temperature

Mushrooms grown at lower temperatures tend to be meatier and of higher quality, although they grow more slowly. The ideal temperature range for growing mushrooms is between 55 and 75 degrees Fahrenheit. You can use a thermometer or temperature sensor to monitor the temperature and adjust accordingly.

Add Light

With lighting, it is recommended to have the lights on for 16 hours and off for eight hours. LED lights can be used, and there is no particular spectrum that needs to be included in the lighting. The advantage of an indoor mushroom fruiting room is that you can grow year-round.

Harvesting: by hand, before spores drop

Straw mushrooms, or Volvariella volvacea, are cultivated in the warm, tropical climates of East and Southeast Asia, where they are also native. They are grown on rice straw beds and are harvested by hand.

When growing straw mushrooms, it is important to harvest them by hand before they drop their spores. You will know they are ready to drop spores when the caps start to curl upwards. If the mushrooms appear to have a powder all over them, they have likely already dropped their spores. This is not ideal, as some people can develop an allergic reaction to spores over time, so it is best to avoid a high spore load, especially when growing indoors.

To harvest straw mushrooms by hand, simply twist them off at the base with your hand. You can usually get about 5 lbs of mushrooms from a 20 lb log, depending on the species. Straw mushrooms can be harvested in their young or mature state. The young, unopened mushrooms are labelled as "unpeeled", while the opened mushrooms are "peeled". Unpeeled mushrooms are the most popular version sold in local markets in Asia, as they are believed to have a higher nutritional value and a stronger flavour.

Oyster mushrooms are another variety that can be grown on straw and harvested by hand. They are easy to grow, colonise fast, and fruit heavily. Oyster mushrooms come in many different forms, including blue, pink, yellow, pearl, and king oysters. All have slightly different environmental preferences, and some will be more productive or faster on straw than others.

History: cultivated in Asia for thousands of years

Straw mushrooms, or Volvariella volvacea, have been cultivated in Asia for thousands of years. Native to China, they have been growing wild since ancient times, with the earliest record of cultivation dating back to the 18th century. Buddhist monks at the Nanhua Temple in China grew the fungi on paddy straw for its high nutritional value and medicinal properties. The popularity of straw mushrooms spread across China, even becoming a gift for royalty. Today, they are still one of the most popular varieties consumed in Asia and are cultivated on various agricultural waste substrates, including cotton waste, compost piles, grass, leaves, and wood chips. They can also be found growing naturally on termite mounds in Southeast Asia.

The cultivation of straw mushrooms has expanded beyond China and can now be found in Southeast Asian countries like the Philippines, Malaysia, Thailand, and Vietnam. The warm, tropical climates of these regions provide an ideal environment for their growth. Straw mushrooms are often grown on agricultural wastes, particularly rice straw, which gives them their name. They can be harvested in both their young and mature states, with the young, unopened mushrooms labelled as "unpeeled" and the opened mushrooms as "peeled". The "unpeeled" variety is particularly popular in local Asian markets due to its perceived higher nutritional value and stronger flavour.

Outside of Asia, straw mushrooms are available in canned or dried form in regions such as Western Europe, North America, and Australia. However, caution must be exercised when foraging for wild straw mushrooms in these regions, as there is a highly toxic look-alike known as the "death cap" or Amanita phalloides, which can be lethal when consumed. This similarity in appearance has led to unfortunate incidents of misidentification, especially among immigrants from Southeast Asia to California and Australia.

The ease and productivity of growing straw mushrooms have contributed to their long history of cultivation in Asia. They are often grown on pasteurised straw substrates, with wheat straw, oat straw, and rice straw being commonly used. The pasteurisation process involves heat treatment, which kills off most contaminating organisms while allowing some beneficial bacteria to remain. This method inhibits the growth of foreign spores, such as mould, while creating optimal conditions for the mushroom spawn to thrive.

Frequently asked questions