To begin growing shiitake mushrooms in bags, first start with the strain, substrate, and your bags to get the process underway. Learn all about it here

The process of indoor shiitake cultivation on supplemented sawdust is discussed below. These steps take you from substrate preparation and strain selection, to the filling of bags with supplemented sawdust.

Our objective in this process is to efficiently transform substrate into fully colonized mycelial blocks that then produce copious amounts of mushrooms. Here are the first steps:

Step #1 for growing shiitake mushrooms in bags: Strain and formula selection

Choosing the best strain and substrate formula is a critical first step to shiitake cultivation. Based on Fungi Ally trials, either 3790 or 3782 should be used for indoor mushroom cultivation on supplemented sawdust. High yielding fruiting can be achieved with the basic formula put forward in Paul Stamets’ Growing Gourmet and Medicinal Mushrooms. This is a mixture of hardwood sawdust, wheat bran, and gypsum. By dry weight, use 79% sawdust, 20% wheat bran, and 1% gypsum.

At Fungi Ally, this equated to seven 18-gallon totes of sawdust, two and a half 25-lb bags of wheat bran, and 1 gallon of gypsum. Weights were calculated once and then placed into volume which could be easily repeated without constantly weighing. Other farms use home-built mixers which weigh out both substrate and water for each bag through a process known as dry bagging.

Step #2 for growing shiitake mushrooms in bags: Sourcing substrate

This is a process of getting to know your local economy and local agricultural products. It is possible to simply go to Home Depot or other big box stores and order hardwood fuel pellets (HWFP) as a primary substrate. This can streamline production, but typically they are more expensive and wasteful in places where raw hardwood sawdust is available locally, which is most of the US.

Finding a local sawmill that cuts exclusively oak or who will call you when they mill oak is best. Flooring mills tend to be extremely consistent and a great source of sawdust for mushroom farms. Be sure the mill knows not to mix in other dust.

Our sawdust cost $10/yard when delivered in 30-yard batches. Wheat bran and gypsum can be easily sourced from local feed stores. Wheat middlings are usually available from animal feed companies and can be purchased in bulk and stored in silos to get extremely cheap pricing. Both wheat bran and mids can be used as a supplement. Wheat mids generally have more variables and contain germ, bran and sometimes flour all in one. It is best to get the nutritional analysis of this from whoever you are looking to purchase substrate from.

Step #3 for growing shiitake mushrooms in bags: Substrate mixing

The best option for any mushroom farm growing more than 150 pounds of mushrooms a week is a ribbon mixer. This is a piece of equipment designed for the potting soil industry but works great for mixing mushroom substrate.

Substrate is loaded into the mixer and wet during the mixing process. This is the method that Fungi Ally moved onto using after 3 years of mixing by hand.

For more handy and industrious mushroom growers, homemade dry mixers are being developed. This allows the process of mixing and bagging to be combined into one step with sawdust and supplements added dry and then water added individually to each bag. This can all be done using a scale and flow meter to measure the exact amounts of substrate and water desired in each bag.

When mixing, it is better for the substrate to be slightly dry than too wet. When it is too wet, substrate sticks to the bag, which then becomes extremely difficult to seal. Aiming for a moisture content around 55-60% is ideal. At Fungi Ally, this was measured by the “squeeze test” to see if the substrate holds shape but does not drip any water.shiitake mushroom growing in bags.

Step #4 for growing shiitake mushrooms in bags: Bagging and folding

Bagging is one of the more time consuming and repetitive tasks. Bagging and folding is a great example of a seemingly trivial unimportant task having a big impact on the overall success of cultivation. If the area where the bag will be sealed is not clean and well folded, it becomes very difficult to seal. If it is folded with a wrinkle in it, sealing becomes difficult.

Bagging at Fungi Ally was done by hand with a 1-gallon lemonade pitcher. Bags were approximated to 5-6 pounds and weighed occasionally during the bagging process. Many farms are shifting to a 10-lb bag, which decreases labor costs.

When folding by hand, the bag should be folded so the filter is on the inside. This ensures the filter does not get wet and allow for growth of organisms through the filter. Ensure the fold has no creases or extra folds in it, which will make for difficult sealing later in the process. At Fungi Ally, bags were placed in a 300-gallon stock tank with about 200 fitting at a time.

Note: Bag type. For this process of cultivation, filter patch bags are necessary. These bags are specially made for the mushroom cultivation industry. Bags come with a filter, and are made out of a special kind of plastic that does not melt at high temperatures. An impulse sealer is used to melt the plastic to itself creating a seal. Good bags to use are Unicorn with T filter and Tufpak. There are likely other quality bags, but these two have shown the most success.

This next article discusses the process of steaming the bags, inoculating, and incubating the shiitake mushroom bags.

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