Of the many steps in the mushroom cultivation process, incubation is the lengthiest. It is also generally the least involved, where mycelium is left to do what it does best: grow, spread, and colonize a new food source.
Incubation starts directly after inoculation and ends once the substrate has been fully colonized. It precedes the fruiting stage, which typically requires additional moisture and fresh-air exchange compared to incubation.
While this is a relatively hands-off step, the job of a mushroom grower during incubation is to provide the conditions for mycelium to thrive. This mostly means an environment within the preferred temperature ranges of the species you wish to cultivate, although there are other considerations. Without the proper conditions, mycelial growth can slow down significantly, and contamination can flourish.
Other than this, it is also essential to monitor the development of your mushroom block during incubation. This process will be discussed in depth later in the text.
Incubation Context
While this text mainly focuses on the incubation of bulk substrates (straw or sawdust inoculated with spawn), it’s worth mentioning that incubation is also conducted for the production of agar, liquid cultures, and spawn. This will be briefly discussed later in the text.
Incubation Time
Incubation is the lengthiest step in the cultivation process. It can take anywhere from a few weeks to several months. Numerous factors can affect incubation time, as mentioned below.
Factors Influencing Incubation Time
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Strain and Species: Some varieties, like Oysters, can colonize a substrate in just 2-3 weeks. Reishi, on the other hand, can take months. Certain strains within these species may also be faster than others.
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Vigor: The vigor of your culture can significantly influence incubation time. For example, spawn that is too old, poorly colonized, or low in nutrients can grow slower. Cultures that are old or have been reproduced for many generations can also lose vigor, entering a state called “senescence.”
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Inoculation Rate: Inoculation rate simply refers to the ratio of spawn you’ve utilized for your quantity of bulk substrate. As can be imagined, a higher inoculation rate results in faster colonization.
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Substrate: Certain species may have affinities for specific substrates and simply grow quicker on them. Typically speaking, higher nutrient substrates colonize faster. Likewise, some substrates may have compounds that slightly inhibit or slow the growth of certain fungi. Inadequately prepared substrates (excess moisture, poor structure, etc.) may also colonize more slowly.
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Contamination: If your substrate was not adequately pasteurized/sterilized or inoculated, you may have other microorganisms present that can significantly slow down fungal growth. In some cases, your mycelium can overcome contamination, while in others, it can’t.
- Growth Conditions: These are all the environmental conditions like temperature, moisture, fresh air exchange, and light. We’ll go into these more later.
| Mushroom | Incubation Time (Days) | Notes | |
|---|---|---|---|
| Fast Growers | Pink Oyster (Pleurotus djamor) | 14-21 | Fast colonizer, prefers warmer temperatures |
| Oyster (Pleurotus ostreatus) | 14-28 | White, gray, blue, and other common oyster varieties typically only take 2-4 weeks. | |
| Pioppino (Agrocybe aegerita) | 14-28 | Similar to Oysters in colonization speed | |
| King Oyster (Pleurotus eryngii) | 21-30 | A bit slower than other Oysters | |
| Lion's Mane (Hericium erinaceus) | 21-35 | Prone to early pinning but typically ready in less than a month. | |
| Medium To Slow Growers | Shiitake (Lentinula edodes) | 60-90 | Depends on substrate and strain. Shiitake undergoes various steps during incubation which are discussed later in the text. |
| Reishi (Ganoderma lucidum) | 60-90 | It can be pretty slow and tends to like warm temperatures. | |
| Turkey Tail (Trametes versicolor) | 60-90 | A robust colonizer, but can take time to permeate the substrate fully | |
| Maitake (Grifola frondosa) | 60-120 | One of the slower cultivators. | |
| Nameko (Pholiota nameko) | 60-120 | Ninety days is about average, and the same as Chestnut mushrooms. | |
| Very Slow Growers | Any Species On Logs | 120-360 | Logs are significantly slower at colonizing due to their density. The benefit is that once colonized, they can produce for 4-8 years. |
Growth Conditions
Temperatures
Above all other factors, proper temperature is the most critical environmental condition to consider during incubation. Temperatures outside of the preferred range for specific species can significantly impede fungal growth or cause the proliferation of contaminants.
Every species has its preferred temperature range. Some like it cooler and make excellent winter crops, while others flourish in warm tropical conditions. It is essential to adequately maintain temperatures for the specific species/variety you are cultivating. Likewise, it is recommended to choose species that fit your local temperatures. Some growers switch their cultivars depending on the season to minimize the need for temperature control.
If you do not have automatic temperature control you may want to find ways to control temperatures passively if needed. This can be as easy as opening windows/doors to allow fresh air in or wetting the floors to promote evaporative cooling. Thick curtains on your windows can also be great for promoting cooler temperatures in the summer. This really depends on your set-up. A digital thermometer is recommended in your incubation space to monitor highs and lows.
Generally speaking, about 70°F (16°C) is an excellent temperature for many species. Some growers keep their incubation rooms around this temperature to cultivate many varieties at once.
Lastly, you should also consider that the fungi produce heat, and their internal temperatures may be a couple of degrees above ambient air temperature. This can lead to overheating, especially if many mushroom blocks or buckets are close together in a small environment. For this reason, avoid having bags/buckets too close together or touching, always leaving a small gap for air flow.
| Mushroom | Ideal Incubation Temperature (°F/°C) |
|---|---|
| Cold Tolerant Species | |
| Enoki (Flammulina velutipes) | 50°F-60°F (10°C-16°C) |
| Pioppino (Agrocybe aegerita) | 50°F-60°F (10°C-16°C) |
| Turkey Tail (Trametes versicolor) | 65°F-75°F (18°C-24°C) |
| Lion's Mane (Hericium erinaceus) | 65°F-75°F (18°C-24°C) |
| Shiitake (Lentinula edodes) | 65°F-75°F (18°C-24°C) |
| Grey Oyster | 70°F-75°F (21°C-24°C) |
| Maitake (Grifola frondosa) | 70°F-75°F (21°C-24°C) |
| Intermediate Tolerance | |
| Chestnut (Pholiota adiposa) | 70°F-75°F (21°C-24°C) |
| Italian Oyster (Pleurotus pulmonarius) | 70°F-75°F (21°C-24°C) |
| Nameko (Pholiota nameko) | 70°F-75°F (21°C-24°C) |
| White Oyster (Pleurotus ostreatus) | 70°F-75°F (21°C-24°C) |
| Black Pearl Oyster (Pleurotus ostreatus var. "Black Pearl") | 70°F-75°F (21°C-24°C) |
| King Oyster (Pleurotus eryngii) | 70°F-75°F (21°C-24°C) |
| Blue Oyster (Pleurotus ostreatus var. columbinus) | 70°F-75°F (21°C-24°C) |
| Warm Tolerant Species | |
| Pink Oyster (Pleurotus djamor) | 75°F-85°F (24°C-29°C) |
| Golden Oyster (Pleurotus citrinopileatus) | 70°F-80°F (24°C-27°C) |
| Reishi (Ganoderma lucidum) | 75°F-80°F (24°C-27°C) |
| Note that the temperature tolerances of species can vary greatly depending on the specific strain being cultivated. For this reason it is recommended to take these temperatures with a grain of salt, and ask your spawn provider for more information about the strain if possible. Consider that most varieties do best at intermediate temperatures despite having tolerance one way or the other. | |
Fresh Air Exchange (FAE) and Humidity
Fresh air exchange (FAE) and humidity are not as crucial during incubation compared to fruiting. While not necessary, keeping these low during incubation can deter early pinning in some species.
- Fresh Air Exchange (FAE) simply refers to the renewal of air from an outside source to replenish oxygen and reduce carbon dioxide levels.
- Relative Humidity (RH) refers to how much moisture is in the air. While maintaining a high RH is important during fruiting, the substrate should contain enough moisture for mycelial growth during incubation.
Light
It is recommended to incubate in darkness as light is not necessary or beneficial during this stage. That being said, indirect light is usually harmless. Direct sunlight is never recommended. Some varieties may be prone to early pinning when exposed to light.
Monitoring
While incubation is generally a hands-off process, it is recommended to monitor your grow kits routinely during this process. While it’s tempting to check on your bags the day after inoculation, monitoring really only needs to start after about 4-5 days at the earliest.
Things To Consider When Monitoring Your Grow Kits
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Handle Gently: If possible, avoid handling the grow kits or uncolonized bags during incubation. If you need to move a bag or check in more detail, grab it gently and avoid applying pressure on the growing substrate. While this isn’t catastrophic, it could stimulate early pinning and disrupt growth.
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Checking For Contamination: When monitoring your block, check them for contamination. If you see greens, blues, reds, blacks, or other signs of mold, remove it from the incubation area and set it aside. Some species, like Oysters, can overcome contamination. This being said, it’s best to separate them from other grow kits or bags to avoid spreading the contamination into your incubation space. In a future article, we will discuss how to identify contamination.
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Fungus Gnats: Unless you’ve got a well-contained incubation area, you’re likely to see the appearance of fungus gnats. These pesky critters can sniff out the mycelium, and if they have access, they will use it as a food source. Ensure your containers are well-sealed and attempt to remove the source if possible (old grow kits, compost, fruits, veggies, etc.)
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Break and Shake: Depending on how you inoculate your substrate, you may have uneven mycelial growth. In this case, you can “break and shake” to redistribute the mycelium and promote quicker colonization. You should only have to do this once when you are at about 10% colonization.
- Checking Progress: An essential part of monitoring is to check the growth rate of your mushrooms and how close they are to being fully colonized. If your mycelium is growing slowly, you may have had issues with your culture, or your environmental conditions may be off. Sometimes, you just need patience. Fully colonized bags should be moved to their final fruiting conditions.
Recognizing Full Colonization
Recognizing when your mushroom substrate has reached complete colonization is a crucial step in cultivation, marking the transition from incubation to fruiting. While some mushrooms will naturally pin when fully colonized, others must be triggered or placed in proper conditions for this to start.
- White Mycelium: The most prominent feature of a fully colonized substrate is the dense white mycelium. The substrate should be unrecognizable and thoroughly permeated by the mycelium.
- In some species, like Reishi, yellow or red liquids known as exudates can accumulate in the bag. This is normal.
- Shitake is unique as it is only ready to fruit after the block has turned completely brown.
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Pins Forming: Generally, if you see pins forming, the mushroom is ready to fruit. Some species, like Lion's Mane, may be more susceptible to early pinning.
- Density: A fully colonized substrate is typically dense with high structural integrity. If gently squeezed, the substrate shouldn’t nudge.
Transitioning To Fruiting
It's essential to transition the colonized substrate to the fruiting phase promptly. Prolonging incubation beyond total colonization leads to the mycelium consuming nutrients that could otherwise be used for mushroom production, potentially impacting yield. If you need to delay fruiting, consider cooling the substrate to slow down mycelial growth.
While we go into this in more detail in our “Introduction to Fruiting” article, fruiting conditions require plenty of FAE and humidity. Some species may prefer distinct temperatures during fruiting compared to incubation.
If your mushroom block is not fruiting despite being fully colonized, you may need to trigger it to get it to fruit. If you think moisture could be an issue, you can fully submerge it to rehydrate the substrate. Some species, like Enoki and Shiitake, are triggered by lower temperatures. This can often be achieved with a cold dunk, but placing them in a cooler is also an option if you're only growing small-scale.
Incubating Agar, Liquid Cultures, and Spawn
When incubating agar, liquid cultures, and spawn, it is vital to monitor your cultures actively. Since these are utilized for inoculating another substrate, you want to get them when they are actively growing and just before full colonization. While you can still use them after this point, they may be less vigorous. Storing in a fridge or another cold environment is a great way to slow growth if necessary.
- Agar: Agar typically incubates for 1 to 2 weeks maximum. Once your plate is about halfway colonized, consider cold-storing until it is ready.
- Liquid Culture: Liquid culture grows quickly and can be used in less than a week.
- Spawn: Spawn usually takes 1-4 weeks, depending on your process. Agar and liquid culture inoculations are typically much slower than grain-to-grain inoculations. When your spawn is about 1/4 colonized, it is recommended to “break and shake” to spread around the mycelium and allow for more even colonization.
Conclusion
While it’s easy to be eager for the growth of your fungi, incubation is a necessary process that should be undertaken with patience. I recommend “set and forget” anything for at least a week because that’s about how long it takes to see anything at all. Hide it in your closet or somewhere dark, and set an alarm if necessary. Before you know it, your fungi will be ready for fruiting!
PS: Staring doesn’t make it grow quicker!
