Mushrooms Multiply: A Guide To Mushroom Reproduction

Mushrooms are the fruiting bodies of fungi, which are unique organisms that are neither plants nor animals. They grow from fungal spores that thrive in damp, dark conditions with high levels of humidity. Unlike plants, mushrooms do not grow from seeds and do not require sunlight, making them popular among urban farmers. Instead, mushrooms grow from spawn, which can be purchased from commercial labs and mixed with a substrate to provide the necessary nutrients for growth. They can be grown indoors in a controlled environment, on logs, or even in kits designed for beginner mushroom growers.

Mushrooms are fungi, not plants

Mushrooms are fungi, and not plants, for several reasons. Firstly, fungi and plants are distinct kingdoms, with no common ancestor in the last half a billion years or so. Fungi are, in fact, more closely related to animals than plants. This is supported by molecular evidence, which also provides robust evolutionary histories and indicates organismal relationships.

Fungi and plants also have different biological processes. Unlike plants, fungi do not have chlorophyll for food production. Instead, the mycelium of a fungus grows into and around its food source, secretes enzymes for external digestion, and then absorbs the nutrients. Fungi also require oxygen to thrive, while expelling carbon—the opposite of plants.

Fungi have a unique growth process. When spores land in the right environment, they germinate and send out a small filamentous thread called a hypha. Fungi grow from the tip of the hypha, extending forward in response to outside stimuli. The growth patterns are thought to be organised and directed by an organelle called the Spitzenkorper. Fungi also have cell walls containing chitin, a compound found in the exoskeletons of arthropods.

Fungi play a crucial role in decomposition, breaking down complex organic compounds and lignin, a key component of woody matter. This enables the degradation of forests and contributes to nutrient cycling and carbon sequestration.

The misclassification of fungi as plants in the past has led to curious events and impacted how we understand and engage with these organisms. However, it is important to recognise that taxonomic classifications are constantly evolving as our understanding of the diversity of life deepens.

Different species, different growth rates

The growth rates of mushrooms vary across different species. For instance, the Reishi (Ganoderma lucidum) is a slower-growing species, which may develop a more concentrated profile of beneficial compounds over time. Oyster mushrooms, on the other hand, take 3-4 weeks to become fully colonized.

Shiitake mushrooms have their own specific requirements for growth. They are grown on sawdust blocks and require two extra steps for colonization. After full colonization, the block becomes textured and bumpy, and eventually turns brown. It is important not to disturb the shiitake blocks during incubation until 75% of the block has turned brown.

The growth of Tremella mushrooms is unique, as they require parasitizing another host species. They start as slime molds and once they encounter another species of fungus, they exhibit aggressive mycelial growth and eventually fruit. Cultivators need to grow both the parasite and the host together to produce this mushroom commercially.

The growth of Shaggy Mane mushrooms, or Shaggy Ink Caps, is also noteworthy. They are cultivated on manure-based substrates in bags or trays, or outdoors in straw beds. However, they have a very short shelf life, as they can turn into a black goo within a day of harvest.

The growth rates of mushrooms are influenced by various factors, including substrate quality, environmental conditions, and storage conditions. Substrate quality, for example, can impact the nutritional content of mushrooms. Additionally, environmental factors such as temperature, humidity, and air exchange play a crucial role in optimizing growth rates.

Temperature and humidity control

Temperature and humidity play a crucial role in ensuring successful mushroom cultivation. Mushrooms are highly sensitive to their environment, and maintaining a consistent level of humidity is critical for their development. The ideal temperature and humidity levels vary depending on the mushroom species and its growth stage. For example, oyster mushrooms thrive in a temperature range of 55-60°F and 80% humidity, while button mushrooms require a temperature of 75-77°F for mycelium growth and then a temperature range of 53-60°F and 90% humidity once the mycelium is fully formed.

To control temperature levels when growing mushrooms, a thermometer or temperature sensor can be used to monitor the temperature of the growing medium and the surrounding environment. This information can then be used to adjust the temperature as needed, using tools such as heating pads or mats, and cooling fans. Heating pads and mats can be placed underneath the growing container to provide a steady source of heat and are available in different sizes to cover the entire growing area. Cooling fans can be used to increase air circulation and quickly lower the temperature, preventing the mushrooms from overheating.

Maintaining the ideal humidity level for growing mushrooms is essential, as both low and high humidity can have detrimental effects on their growth. If the humidity is too low, mushrooms can dry out and become stunted, and if it is too high, it can lead to mould growth and other issues. To control humidity levels, methods such as misting spray bottles, pond misters, and fans can be employed. Pond misters create a fine mist of water in the air, providing consistent humidity levels, while fans help distribute moisture evenly and reduce the risk of condensation and mould growth.

For commercial mushroom cultivation, climate-controlled grow rooms and advanced environmental systems are required to provide the specialised controlled conditions necessary for large-scale production. These systems can be monitored and adjusted using smartphone apps, allowing for constant oversight of the mushrooms' health. By understanding the mushroom life cycle and regulating temperature and humidity during each stage, growers can optimise their setup for healthy and abundant yields.

Initiation: mycelial growth to mushroom formation

Mushrooms are the fruiting bodies of fungi. They grow from fungal spores that thrive in damp, dark conditions. Fungi take cues from their environment to begin forming mushrooms. Changes in humidity, temperature, and moisture are major determining factors for when mushrooms grow. Each species of mushroom has a particular preference.

Mushrooms are not plants, and therefore require different conditions, facilities, and equipment to grow. They do not require sunlight and can be grown indoors, making them popular with urban farmers.

Mushrooms grow from mycelium, which uses the substrate for nutrients. Mycelium is a network of thread-like roots that can be found in the soil or other growing mediums. Mushroom spawn is mixed with the substrate and transferred to beds or trays. A casing made of peat moss is spread over the bed, serving as a reservoir to hold in moisture.

During the pinning stage, "pins" of mushrooms push up through the casing. The physical mycelium matter remains mostly the same during fruiting, but the mushrooms can grow so much in a short time because they grow by expansion, rather than cell division. This means that water is being added to the cells to create a bigger body.

Harvesting and storage

When harvesting mushrooms, it is important to consider the sustainability and conservation of the crop. Mushrooms are the fruit of a much bigger organism, and their main purpose is to produce spores to help the plant reproduce. Therefore, it is important to ask: "Do I really need to pick this mushroom?" and "How can I ensure there will be mushrooms in this location in the future?".

There are different methods for harvesting mushrooms depending on their variety and habitat. For mushrooms that grow on the forest floor, it is best to gently push the mushroom at the base of the stalk and pull it up. Any dirt can then be trimmed from the base, and debris cleaned off. For mushrooms that grow on the trunks and stumps of trees, such as oyster mushrooms and cauliflower fungus, they must be cut off with a knife. It is important to never let dirt enter your collecting basket or bag. You can use baskets, cloth, or even recycled plastic bags while harvesting, but when you return to your vehicle, the mushrooms should be placed in a packing basket with mesh sides or a wicker basket.

Mushrooms are perishable and will begin to deteriorate as soon as they are picked, so proper drying and storage are vital to avoid degradation and to prevent the appearance of mould. Mushrooms can be dried by placing them on a rack or mesh in a single layer, without stacking them, ensuring there is enough space between them for air circulation. You can also put them on kitchen paper. If the mushrooms are large, it is best to cut them into sheets and let them dry.

Once dried, mushrooms should be stored in airtight containers with desiccants, in a cool, dry, dark place. Refrigeration can be used for long-term storage, but exposure to moisture should be avoided. These steps will ensure that mushrooms maintain their potency and quality for as long as possible.

There are other preservation methods for wild mushrooms, such as airing, freezing, pickling, and infusing. Pickling with salt, vinegar, and sugar is a relatively safe method of preservation, but it is a complicated process. Freezing mushrooms can be done by first sautéing or blanching them, or simply slicing them, laying them on a cookie sheet, freezing them, and then storing them in a bag. Frozen mushrooms should be added straight to dishes without thawing.

Frequently asked questions