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shiitake Fruiting blocks!

Blue Sky Fungi fruiting blocks are made of fully colonized sawdust and small wood chips that are supplemented with wheat bran and gypsum. The composition of the fruiting block depends on the species of mushroom. Most mushrooms will require certain conditions (temperature, humidity, CO2, and light) in order to properly grow and are detailed in each section.

You can purchase one from us here!

Special Note: Do not open your mushroom fruiting block until you have read through ALL these instructions and prepared all the necessary materials. Before you begin, make sure that the mycelium block was not cracked or broken apart within the bag. If the block is cracked, place the sealed bag in a dark place and don’t move it around. Allow the mycelium to recover and regrow for a few days undisturbed. If it starts growing mushrooms, it is ready.

ALWAYS!!! use non-chlorinated water to rinse the block with. Well water is good, but if your tap water is chlorinated, you can use filtered water or leave an open container of water out overnight to dissipate out the chlorine naturally

Placement Indoors: Find a place inside that is of average room temperature, has indirect lighting (enough to read words on a page, but not in direct sunlight), and away from drafty air currents, fans,  heat sources, and materials that are porous like wood surfaces or carpets (spores drop from the mushroom).

Use of a Humidity Tent: Sometimes a location will require the use of a humidity tent, which is basically an oversized plastic bag with many holes. The idea is to make an environment that holds humidity/moisture and will allow fresh air to enter (and CO2 to exit). You do not want the humidity tent to be touching the block, but rather creating an environment around the block. The humidity in the tent can be maintained with a spray bottle. Lift up the tent/bag and spray the fruiting block and the inside of the plastic bag so it appears moist and water droplets are visible, or you can just spray through the holes in the plastic bag.

Do this 2 to 3 times a day (or more if warm, dry conditions exist). Place a pie-pan or broiler pan under the fruiting block to collect the water.

Shiitake (Lentinula edodes)


Temperature - 50 to 75 degrees F        Humidity - 60 to 80 %

The Shiitake mycelium will have a white and brown bark/skin on the block. If little mushrooms are forming up against the bag, the block is ready to initiate.

The block can be initiated without little mushrooms forming.

Initiating Fruiting: A cold shock can stimulate mushroom formation with the Shiitake mycelium. You can do this by placing the sealed block outside on a cold night (at least below 50 degrees F), or by placing the sealed block in the refrigerator, for 8 to 12 hours. If little mushrooms are already forming on the surface of the block, you can just open the bag without the cold shock. And if the mushrooms have been growing large and got smashed up against the plastic bag, you can cut off those deformed ones to make room for the new mushrooms.

Setting up: Always clean your hands before you touch the mycelium. After the cold shock period, remove the fruiting block from the cold temperature. Cut the bag and remove the block from the plastic (try not to cut the mycelium block). Run cold water over the surface of the entire block for 10 to 15 seconds in your sink or in the shower if the block is too big for the sink. You can also fill a bucket with non-chlorinated water and submerge the entire block for this time (longer time is fine).

Bring the block to the space you want to grow the mushrooms (see above) and place it over a bowl or pie-pan. The ideal placement would be to span the block from the edges of your bowl so it does not touch the bottom. That way you can have a little pool of water at the bottom for additional humidity. You can place the block outside if the right conditions are present, but you open the mushrooms up to bugs or other creatures that eat mushrooms.

Daily Care: Now that your mushroom fruiting block is set up, you need to perform some daily care. Rinse the block with cold water or submerge it in a bucket at least once a day. Twice is ideal. Did you remember to wash your hands first? Change the water at the bottom of the container when you rinse off the block. Once the mushrooms get bigger or the block is harder to move, you may use a spray bottle to keep the mycelium surface moist. when using a spray bottle, mist the block for at least 45 seconds, twice daily.

Harvesting: Mushrooms should start to form 4 to 7 days after initiating. You can continue to water the block while it has little mushrooms growing, but try to avoid getting a lot of water into the underside (gills) of the mushrooms. The ideal harvest will be when the cap starts to roll away from the stem to expose the gills. Younger mushrooms are more dense and have a better shelf-life. You can let the mushrooms grow bigger if you like, but be aware that once the gills are exposed, the mushroom will be dropping spores. You can stop watering them a day before you harvest to let the caps dry out a bit. Ideally harvest them all at once, but you can wait 1 or 2 days if you want some to grow bigger. Cut the stems all the way to the surface of the block


Don’t get rid of the block. Shiitake will produce several flushes of mushrooms, but you will need to rest the mycelium and let it build up energy for a rebound. The mycelium is moving farther into the block and eating more of it for nutrients.

Let the block rest in a dry area for 7 to 10 days. Do not water the block!!

You want the mycelium to harden on the outside of the block to conserve it’s internal moisture.

Once you are ready to re-initiate the block for another flush of mushrooms, soak the block in a bucket of cold water overnight (about 8 to 12 hours). The block will want to float, so you may need to place something on top of the block to submerge it. A plate or lid works well. After soaking, return the block back in your mushroom fruiting location and resume the daily care.

You can expect at least 3 flushes of mushrooms from these blocks, but we use fresh Oregon white oak sawdust, so as many as 5 flushes with our 4 pound blocks is possible! If no more mushrooms form after the soaking, you can try to rest it and soak it again. If to no avail, then the block is exhausted and will make excellent mulch or compost for your garden

For a PDF copy of the Shiitake Fruiting Block Instructions, click here.