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shiitake mushroom Fruiting blocks!

You can purchase one from us here!


Blue Sky Fungi Shiitake fruiting blocks are made of fully colonized oak sawdust and small wood chips that are supplemented with wheat bran and gypsum.

Shiitake Good.JPG

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 1 or 2 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 85 degrees F        Humidity - 60 to 85 %

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 grow.

Growth 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 and above freezing), 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. 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 decomposing (eating) more of the wood 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 soaking again yields no pinning, then the block is exhausted. It is now excellent mulch, wonderful food for your worm farm or compost for your garden … or a yard ornament that may give you surprise mushrooms later.

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

frequently asked questions

Mycelium require certain conditions to produce a mushroom. These conditions include specific temperature, humidity levels, CO2, and light. Many problems encountered with growing mushrooms are a result of an imbalance of these conditions. The solution is to manipulate the environment to be favorable for the mushroom to produce and survive. The following section will answer some frequently asked questions about growing Shiitake mushrooms from a Blue Sky Fungi fruiting block.

The block is not producing mushrooms and feels light and dry.

This is most likely a problem of humidity and available water. You should be hydrating the block at least once a day, but if your growing environment is too dry, you may need to hydrate it more than that. Placing a plastic humidity tent over the block will help retain the moisture for the block. Remember to always use non-chlorinated water! Rinsing under a faucet, with a hose, or dunking the whole block in a bucket of water for 10 to 20 seconds are good ways of hydrating the block. Make sure you properly soaked your block when conducting subsequent flushes.

I am hydrating the block daily but the mushrooms still won't grow.

This is most likely a problem of timing. The Shiitake mycelium will go through a mushroom growth phase of 7 to 12 days, in which daily hydrating is required. Then it will go through a recharge phase of resting and drying for 7 to 12 days. After that, soak the block overnight to rehydrate and begin the growth phase. Success will be limited if you just keep wetting the block and trying to continuously grow mushrooms without a proper rest/recharge phase. Check to make sure the growing environment is also appropriate.

Mushrooms are only growing out of the bottom of the block.

This is most likely a problem of humidity. The growing environment may be too dry and the use of a humidity tent will be necessary. Place a plastic bag that is big enough to fit over the entire block and try not to let it touch the sides. Cut some holes in the bag to promote air flow. If you can catch the mushrooms when they are still small on the bottom, you may flip the block over so the little pins are now on the top.

The mushroom stems are really long and the caps are small!

This is most likely a problem of CO2. Mushrooms are like us: they breathe oxygen and exhale carbon dioxide. The long stems are a direct response of too much CO2. Put more air holes in the humidity tent, or try to move the air around the block to prevent the CO2 from pooling in the low spaces.

A few mushrooms are already growing in the sealed bag and are smashed up against the plastic, what should I do?

This happens when you wait too long to start the growth process. The Shiitake blocks are ready to produce mushrooms when you receive it, but sometimes life gets in the way for you and prevents you from removing the block from the bag. Most of the time the mushrooms are forming on the bottom or the sides and pressed up against the plastic. If you catch it when the mushroom is small, you can continue to grow the smashed mushroom when you open it, but it will grow with the deformity. If the mushroom is big and starts to look wet and brown, it is probably dying and should be cut off and discarded. Continue with the growing instructions after you have removed all of the deformed mushrooms.

It looks like bacteria or mold is growing on the surface of the block.

Competitor organisms are everywhere and opportunistic. It is not uncommon that small blotches of bacteria or mold will grow on the surface. Bacteria and molds are generally shades of green, yellow, blue, spotty white, and black. Shiitake will naturally look white, chocolate brown, and dark brown. Wait to take care of this until after you have harvested your mushrooms. Use hydrogen peroxide or very dilute bleach dabbed gently on the infected areas. You can scrape off infected spots with a paper towel after treating them with perioxide. After the bacteria or mold has been removed, allow the block to dry during the rest phase. The lack of water will discourage further infection growth. If the surface contamination cannot be overcome, it may be time to retire the block to the outdoors. You can set it outside in a shady spot and allow it to get wet. The outdoor conditions may be favorable for mushrooms to continue to grow.

Is it safe to eat the mushrooms if mold is growing on the block?

Short answer is: yes, if you are cooking the mushrooms. This is one of the many reasons why it is important to cook all mushrooms. Most of the time the infection is growing on the skin of the block and is benign to the mushroom. If the mold or bacteria has spread to the mushrooms, then probably not, but mushrooms in the wild generally will host a community of organisms. If you are in doubt, compost the mushrooms, clean the block, dry it, then try again.

What if the block breaks or the corners on the bottom break off when it is removed from the plastic bag?

This is no big deal as the mycelium will heal itself back together. So if the corners break off when the block is removed from the bag, proceed with the instructions and discard the broken off corners. However, if a significant crack in the block has resulted from transport or an accidental drop, allow the block a few days to recover and heal itself. You can place large pieces back together, tied with string works very well, and don't move it for a few days. If the broken block is still in the grow bag, leave it in and don't open the bag; let it recover for a few days before opening and proceeding with the instructions.

What if I go away for a few days or weeks while I'm growing the mushrooms?

Harvest the mushrooms before you leave and let the block stay in the rest/recharge phase. You don't need to care for the block in this phase, so enjoy your time away. When you come home and are ready to fruit more mushrooms, soak the block overnight and begin the growth phase again. You may return to a few small dry mushrooms growing on the block. Simply harvest that mushroom and perform the overnight soak to begin the growth phase again.

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