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Baby Steps
Shiitake Cultivation Basics
Shiitake cultivation is neither as hard nor as mysterious as it is often portrayed. The truth of the matter is that if you have good spawn (which isn’t a simple task) and a properly incubated block, the substrate could be plopped on your kitchen countertop and it would produce fruiting bodies. It is equally true that if you are growing shiitake to make money and have to pay wages and loan payments on equipment, that it often pays to take some steps to maximize your yield. It doesn’t have to be super complicated, but there are some basic best practices to follow, and a few parameters shiitake growers should be keeping data on for their operation.

Shiitake are a saprophytic fungus; in nature they break down wood from dead, fallen trees and obtain nutrients as they decompose the wood. Saprophytic fungi are an incredible branch of nature, one which is adapted to break-down lignin, a complex polymer that is highly resistant to degradation, as well as cellulose and other compounds in wood. Shiitake grow on broad-leaf deciduous trees in nature, with particular affinity to the beech and oak families. They also grow on maple wood, mahogany, apple wood, and can even be grown on alternative grass and weed based substrates. The latter is not appropriate in this context, because it is highly complex process, entailing fermentation and careful balancing of the C/N ratio as well as nutrition supplements and produces subpar shiitake that tend to have elevated traces of pesticides and heavy metals in them.

Substrate Mixing
The basics of shiitake cultivation are actually far simpler than trying to create compost for Agaricus cultivation, but there are some points the two share. As with straw for Agaricus compost, for shiitake, you want relatively fresh sawdust and very fresh wheat and rice bran for the best and most consistent yields and lowest contamination risks. But that’s it in terms of raw materials. That’s why I always find it weird that so many people involved in the mushroom industry who are only familiar with Agaricus varieties say shiitake are so difficult and expensive to deal with. Growing shiitake requires reliable deliveries of fresh sawdust and a warehouse or covered building to store sawdust in; no fermentation or composting is required, nor is there any delicate balance between phase two or phase three compost to calculate, no adding nitrogen or timing the cookout. Making compost for Agaricus cultivation is far more difficult than literally anything required to cultivate any exotic mushroom variety.

Now I’ve mentioned nutrition supplements. 100% sawdust substrate will absolutely produce shiitake, but without nutrition supplements this process is inefficient and the yields suffer. There is a delicate balance that can get complicated as strain variety and grower priorities (do you want more pinnings, or do you want larger average size for your shiitake) come into the picture. However, there is a basic formula. Japanese farms generally use nine parts sawdust to one part nutrition supplement, which is a mixture of wheat bran and/or rice bran from mills (with the default a 1:1 ratio). Corn bran and/or sorghum bran might also work as nutrition supplements, but the ideal ratio may change. The idea is to add more carbohydrates and easy-to-breakdown proteins in order to promote faster mycelial growth and better yields, but the tricky part is that adding too much causes too many small pinnings to pop up or increases pinning failures.

When preparing substrate there is an order of operations. Add sawdust to the mixer and start turning it. Then add your nutrition supplements and only after the supplements and sawdust are well-mixed dry, do you add water. The reason is that you want the nutrition supplements to be relatively evenly mixed with the sawdust. Wheat bran and rice bran absorb water more readily than sawdust and tend to clump otherwise, which is going to create very inconsistent substrate. Inconsistent substrate means inconsistent yields and quality. Experience is sufficient to tell if a substrate has enough water just by squeezing it between your hands, but “hand-feel” isn’t a unit of measurement, so farms should take small samples of each batch and test the water content. Keep a record on what the water content in each batch of substrate is. Japanese growers aim for a total moisture content of the substrate between 62~65%.

Incubation Parameters
A typical incubation temperature for shiitake at Japanese farms is between 20~22 degrees Celsius (or roughly between 68~72 degrees Fahrenheit). This is a middling figure as there are some low temperature strains of shiitake where the incubation is done at 18 degrees Celsius (64 F). In bag cultivation of shiitake, the large majority of common strains are incubated at 22 C (72 F). Incubation typically takes between 100~130 days, though some strains, with the proper settings, can finish in 80-95 days. I’ve noticed many of the strains with shorter incubations also tend to prefer cooler settings. Trying to speed up the incubation too much can result in poor quality shiitake and reduced yield or even failure to produce fruiting bodies, but allowing incubation to continue too long also leads to pinning failures and reduced yields.
Humidity during incubation should be kept between 70-80%, and levels of oxygen and carbon dioxide should be as close to their regular atmospheric levels of 22% and .03% respectively as possible. CO2 levels of greater than 3000 ppm will begin to suppress mycelial growth and interfere with the incubation process, so proper ventilation systems are very important for this part of shiitake cultivation.

In Japan, shiitake incubation is roughly split into three periods. During the first period, you see the fastest pace of mycelial spread and high levels of metabolic activity in the substrate. It is very critical to maintain proper oxygen levels and ventilate properly during this period. Due to the mycelial growth, more heat is being generated during this period as well, so farmers typically maintain the room temperature 1~2 Celsius lower during this period to prevent the temperature within the substrate blocks from rising too much.

After roughly thirty days, you enter the second phase of the incubation. This is the point in which the mycelia have spread throughout the block and it has turned white or almost white. The second phase lasts up until approximately the seventy-day point, and during this phase mycelial growth falls off and the substrate begins to get broken down by enzymes secreted from the mycelium. At the start of the third phase, expose the substrate blocks to light. The third phase is when the substrate blocks will change in color again, from white to brown, and management of this period has a big impact on yields and pinning afterwards. Keep careful records of the incubation room conditions, and ensure that humidity stays between 70-80% and temperatures are stable at 22 C (or your strains ideal setting) while increasing ventilation to prevent CO2 levels from raising above 3000 ppm.

Consistent incubation of shiitake through the Japanese bag cultivation system is not that hard or extremely complicated; I’ve worked at large farms that do it for 400 metric tons or more of shiitake a year with minimal labor (a lot of the settings are automated and remotely monitored in a central control room). However, it does require climate control systems, sensors, clean spawn rooms, and autoclaves set to the proper settings. In Japan it is quite common for smaller growers to purchase already incubated blocks, in which case the only thing required is some fruiting rooms (typically just simple, pre-fab greenhouse), pickers, and packaging facilities. Another option is for groups of growers in the same region (in America this might be quite large and sometimes cross state boundaries), to pool resources to create joint incubation centers in order to benefit from economies of scales (it’s always cheaper to produce on large and consistent scales than piecemeal on a small scale).

Harvesting
An inexpensive prefabricated greenhouse and growing shelves are sufficient for fruiting rooms. The things to consider are: ease of movement, efficient use of space, cleaning, maintenance, and the flow of picked shiitake within your farm. Once picked, ideally shiitake should be quickly transferred to cold storage (a few degrees above freezing) until they are packaged, and after packaging, either returned to cold storage or shipped immediately.

Picking shiitake is also not difficult. Japanese farms emphasize physically picking shiitake from the blocks by pinching the base of the stems with your index finger and thumbs and then pulling, but this is frankly less efficient and more time-consuming not to mention more difficult. Most farms outside of Japan clip shiitake with scissors, which also saves time in the packaging room that in Japan is spent sorting through picked shiitake and cutting any large chunks of substrate off stems. The main trick is discerning when to start harvesting and spreading out the harvest over several days. The best quality of shiitake comes when the mushroom cap is just beginning to open. Fully opened shiitake tend to be a little lighter, have poorer shelf-life and are more likely to have insect-damage. What’s more, picking shiitake just as they start to open ensures a good balance of weight and shelf-life, as picking too early can mean picking fruiting bodies that would have grown larger and heavier.

In the packaging room packers should check for insects. Certain species of slugs are attracted to shiitake during warmer months, depending on region and local climate. Black or brown marks at the base of the stem or under the cap of the shiitake indicate that it is already starting to rot and not generally suitable for the fresh market. Shiitake in Japan are sorted into between 8~12 size grades, varying by region and market, which large growers get around by using specialized sorting machines. In practice, outside of Japan there usually no more than 3 size grades (small, medium, large), for growers to need to sort.

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Baby Steps

Shiitake Cultivation Basics