Shiitake Bag Cultivation: The Holy Grail?

Welcome to part 2 of the three-part series about shiitake cultivation. In this series, I compare the log cultivation and bag cultivation of shiitake. If you haven’t read part one, you can find it here.

In today’s article, I will give you a brief overview of the main parts of the bag cultivation of shiitake before finally compare them in part 3. The bag cultivation (or synthetic log cultivation[1]) was developed to produce shiitake all year round to meet market demands. With an average production cycle of 3 to 4 months[2].

Strain selection

In part one, I have talked about the importance of strain selection. If you are coming from log cultivation, I want to remind you that strains used for natural log cultivation are different from strains that are used for sawdust bag cultivation.

What strain you should use depends on several factors like

  • Your local climate
  • Your growing method (indoor vs outdoor)
  • The substrate you have at hand

In general, mushroom strains are divided into three groups – low, medium, and high-temperature strains (Table 1). Hence, the strain you select should match your local climate. While you could adjust the temperature if you are growing indoors, this adjustment comes with higher costs (air conditioning) for running your farm. You should, therefore, calculate if this approach is viable for you.  

Table 1: Shiitake strains classified according to fruiting temperature

Table 1: Shiitake strains classified according to fruiting temperature[3].

Substrate selection

The hardwood comes typically from the same trees which were used in log cultivation.

  • Chinkapin (Castanopsis spp.)[4]
  • Oak (Quercus)
  • Sugar maple (Acer saccarum)
  • American Hophornbeam (Ostyra virginiana)
  • American Hornbeam (Carpinus caroliniana)
  • American Beech (Fagus grandifolia)
  • Sweet Birch (Betula lenta and Bentula lutea)
  • Bitternut Hickory (Carya)
  • Red Maple
  • Sweetgum (Luquidambar spp.)[5]

After you got your sawdust now, it is time to mix it with other ingredients to enhance the growth of your mushroom strain. To do so, you can pick from many different substrate formulas which are out there. Some of them can be found in Table 2.

Table 2: Formulation of sawdust-based substrate for shiitake cultivation

Table 2: Formulation of sawdust-based substrate for shiitake cultivation[6].

The mixing of the ingredients is done either manually or automated via a mixer. After everything is properly mixed, and the substrate reached the optimum hydration (approximately 60%) the substrate is then filled in bags (usually about 2.5kg).

This step is again done either manually or with the help of a machine.


Next up is the sterilization of your bags. For this step you can choose from a variety of methods

  • Autoclave sterilization (121°C, 1-2h)
  • Pasteurization (80°C, 1-2h)
  • Super Pasteurization (100°C, 15h)
  • Scalding (80-100°C, 0.5-1h)

You can find more information about sterilization in my in-depth article “How your Sterilization Method will Impact your Mushroom Yield.

Spawning (Inoculation)

After the sterilization, the bags are then brought into the lab for inoculation. When it comes to inoculation itself, there are two main practices out there. One is mainly practiced in Asia and Australia, the other, mainly in the U.S.

Asia, Australia

  • Top spawning
  • No mixing
  • Bags with plugs
  • Bags 100% filled
  • Small size bags (up to 1 kg)


  • Inoculation rate 5 to 7 %
  • Mixing
  • Bags with patches
  • Bags 2/3 filled
  • Medium size bags (2.5 kg)

I found a third method during my visit to Brazil

  • Inoculation rate 1 to 3 %
  • Top spawning
  • No mixing
  • Bags with no plugs nor patches
  • Bags ¾ filled
  • Small size bags (up to 1 kg)

To understand better the process of inoculation, I wrote another in-depth article on How your Inoculation Method can Impact your Mushroom Yield.

Spawn run (incubation period)

The next step in bag cultivation is the spawn run(ning) or incubation phase. During this phase, the temperature should be kept at 25°C for 1-4 months. After this period, the next and crucial step is called browning. In this step, a bark is formed outside of the block.

This browning is done through oxidation of the mycelia which itself turns reddish-brown. To achieve browning, two standards have been developed (Table 3).

  • Brow-out of-bag: Bags are stripped before browning.
  • Browning-in-bag: Bags are stripped after browning.

The browning itself takes about 4 weeks[7]. As mentioned, this step is critical and can affect the yield. It is therefore suggested to use the brow-out-of-bag method because it “produces a firmer, more resilient synthetic log that will resist breaking during soaking, harvesting, and handling.[8]

Table 3: Comparison of Brown-in-bag and Brown-out-of-bag

Table 3: Comparison of Brown-in-bag and Brown-out-of-bag[9].


After the browning has occurred, the blocks than will get shocked to trigger the pinhead formation. To trigger the formation, you can choose from many different methods

  • Temperature fluctuation
  • High humidity
  • Water soaking
  • Removal of CO2 / air exchange
  • Physical shock
    • Stab
    • Beating
    • Turn the blog up-side down

Usually, a mixture of them is used in order to initiate the pinhead formation. In choosing the appropriate method, you should think about the amount of work which comes with each of these methods.


After the pinhead formation occurred, it takes between 5 to 7 days until you can harvest your first shiitake mushrooms. It is a good practice to drop the humidity to < 60% R.H. 12h before harvesting. This step will increase the shelf life of your mushrooms.

After you have harvested your mushrooms, the blocks need to rest (lag phase). During this time the humidity should be held at 30-50% R.H. while the temperature stays at 21°C. The lag phase lasts for 7 to 10 days.

After that, the blocks get socked for up to 12h (2nd flush), and the cycle starts again. After the second lag phase, the blocks get socked for up to 15h (3rd flush), and the last cycle starts.

In average it takes about 16 to 20 days from the peak harvest of one flush to the peak of the next flush[10].

If you go for three flushes or not depends on you. But you should keep in mind that the yield per flush decreases with each flush, which means there is an optimum between producing new blocks and trying to get more out of the current blocks.

Depending on the strain you selected you can expect an average biological efficiency from 75 to 125 percent[11].

As this article is part of a three-part series you can find the links to the other two articles right here.

Article 1 Log Cultivation: Is it worth it?

Article 3 Log cultivation or Bag cultivation: Which is better?

[1] Royse 2001

[2] Royse 2001

[3] Mushroom Growers’ Handbook 2

[4] Mushroom Growers’ Handbook 2

[5] Mushroom Growers’ Handbook 2

[6] Mushroom Growers’ Handbook 2

[7] Royse 2001

[8] Royse 2001

[9] Mushroom Growers’ Handbook 2

[10] Royse 2001

[11] Royse 2001

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