Fruiting Your Shiitake Mushroom Block

Your shiitake block will initially be white and then begin turning brown over the next 4-8 weeks. Ideally, you should introduce your shiitake block to a fruiting environment when it’s at least 50% brown. As the block turns brown, it will also start to form bumps all over it.

Fruiting conditions

Our Shiitake Mushroom Strains are 3782 and West Wind.
Both are excellent all-year-round strains, with very fast incubation, with quality fruit bodies. They’re very tolerant in humid conditions and suited for pasteurized as well as sterilized substrates.

The main requirement for fruiting shiitake mushrooms is that they need a relative humidity of 85-95% and a temperature range of 14-17 °C.

Low tech fruiting
Preparing your block for fruiting

When you are ready to start fruiting your Shiitake block, give the block a good whack on each side with your hand. You’re aiming to hit it hard, but without breaking it. About the same strength that you’d pat a large dog. Put your block in the fridge overnight.

In the morning take the block out of the fridge and cut open the bag and put it aside to recycle. It’s best to open the block in the sink or the garden as there will be brown liquid (metabolites) that is likely to spill everywhere. Wash the block off under running water for about half a minute to get most of the brown liquid off. These steps simulate a shiitake-laden log falling in a forest as the seasons change.

Fruiting in a bucket
What you’ll need:

• A large bucket
• A brick
• A tea towel

Put a brick inside your bucket and fill the bucket with water so that the water level is a little below the top of the brick. Place your shiitake block on the brick so that it’s above the water and place a tea towel over the bucket. The tea towel helps to keep the humidity up. You can check on it periodically, it usually takes 2-3 days for the first pins (baby mushrooms) to start forming.

Place your bucket inside the house or outside in the shade. If the tea towel gets rained on, it will fall into the bucket and ruin the humidity. If there’s too much sun, it will heat the block up and dry it out.
Fruiting shiitakes from a bucket on top of a brick is a low-tech way of fruiting shiitake

Pros: Simple, unlikely to have contamination issues

Cons: Harder to maintain high humidity, if there’s not enough light getting through, shiitake mushrooms can be paler (and will contain less vitamin D).

Fruiting in a plastic tub
What you’ll need:

• A large clear plastic storage container
• A hand-mister.

A plastic storage container will be used as your fruiting vessel. If you don’t have one, you can get them from hardware and office supply stores. The plastic tub should be as clean as possible before you put your shiitake block in it. Wash it out with hot water and dish detergent, then wipe it down with a clean paper towel.

Once the tub is clean, it’s simply a matter of placing your block in the tub and then opening it once per day to give it some air and a few quick squirts with a hand mister. You can take the lid off the container and use it as a fan to help get some oxygen in. I find that this method works better when the weather is warmer, as the liquid is less likely to pool in the bottom of the container. The main problem you’ll have with this method is bacterial contamination. The block will continue to exude metabolites (brown liquid) that are susceptible to contamination, especially if the block is sitting directly in them. One way to avoid this is to do the same thing as the bucket method and place a brick in the container with water underneath. The liquid metabolites will disperse into the water and you can dump out this dirty water when you are ready to harvest.

Another method that works quite well is to skewer the blocks on spikes in the container. This keeps the blocks off the bottom of the container and prevents them from sliding around or toppling over. It allows you to arrange the blocks to maximize fruiting space.

Shiitake on stakes in a tub
Raising shiitake reduces contamination

You can place the container inside or outside, as long as it’s not in direct sunlight. It’s fine to get a bit of morning sun, especially at the end of autumn, winter and the start of spring. Place your tubs along the north side of the house and they get plenty of indirect sunlight and the mushrooms turn out a nice brown colour.

Shiitake fruiting on stakes

Pros: This is the easiest way to get high-yielding shiitake crops. The clear container also means that the mushrooms will get some sunlight, which means they’re browner in colour and contain more vitamin D.

Cons: Can contaminate more easily if the tub isn’t clean, wrong time of year, or the tub is not opened periodically to allow in some fresh air.

Checking in on your mushrooms each day

For the first few days, open the fruiting container and give the block a couple of sprays with your hand mister. You want to wet each side of the block if starts to look like it’s drying out. In a few days, you’ll see mushroom pins (baby mushrooms). Keep misting the blocks each day for a few more days and then stop misting when the mushroom pins start to look like proper mushrooms. If you mist the block as the mushrooms get larger, they tend to stay wet and have a reduced shelf life after harvesting. Within 7-10 days after placing your block in a container they should be ready for picking. The mushrooms should be doubling in size every day, once they stop growing it’s time to pick them!


Harvesting shiitake mushrooms is fairly easy. I generally harvest all the mushrooms in a single session, unless there are clearly two pin sets at different stages of growth. I’ll get the block, put it on a piece of newspaper and then cut the top mushrooms off the top of it with scissors. After doing this, I’ll turn the block upside down as I find it quicker to harvest the mushrooms from the underside. You can use a knife, or even twist the mushrooms off, I find that twisting them off often rips large chunks of sawdust with it, this means extra cleanup.

Second flushes

When you’ve picked the mushrooms from your first harvest, leave the block somewhere to dry out with good airflow (e.g. on a shelf with a rack). You’re trying to prevent the outside of the block from going mouldy. After 3-4 weeks the block should be very dry, submerge it in water for approximately 12 hours. One way to do this is to fill a bucket with water, submerge the block in it and place bricks or weights on top to hold it under water. The idea is to hydrate the block so that it gets wet, but not so wet that it falls apart. Take the block out of the water, hit it on each side again (not too hard this time as it doesn’t have the bag to hold it together) and put it back in your fruiting container. Repeat the misting routine, there’s no need to put it in the fridge this time.

Disposing of the block

Your shiitake log is completely organic, you can compost it, bury it or add it to your worm farm. Worms love mushroom mycelium, they’ll tear your block apart it a few days.

Dealing with problems

The two biggest problems you’re likely to face are that your block will go mouldy or you won’t get many mushrooms. If your block is going mouldy, it’s too wet and potentially doesn’t have enough airflow. If you’re not getting a good yield, it’s likely the block is too dry and you need to increase humidity by misting it more. It takes a little bit of experience to know what looks right, if you’re unsure it’s better to err on the side of keeping the block a bit drier. It’s better to get fewer mushrooms than no mushrooms at all.