King Oyster Mushroom

The King of Oysters?

Oyster mushrooms come in different forms and colors. The king oyster with its grayish tones is one of the most grown and consumed oysters in the world. The King oyster has mainly two forms; the form that is the most popular is the one with a small cap and thick stem. It is the meaty thick stem of this mushroom that is highly sought after.

In nature, the king oyster is terrestrial and grows on the buried roots of hard woods. It has regular stems and large caps. The mushroom starts with small concave cap that becomes large and curls downwards as it ages.

The mycelium grows very well on malt extract-based agar and supplemented sawdust substrate. It is aggressive enough to colonize the entire substrate within two to three weeks and be ready to fruit.

The king oyster is not as easy to grow as the blue oyster, and it will not do well on just about any substrate like the blue oyster does. However, king oysters aren’t that difficult to work with either. This mushroom is fun to grow, because unlike other oyster mushrooms, the king forms single mushrooms and not clusters. A single king oyster mushroom can get close to 300 grams, which is quite large. 

Although the King oyster can be grown on straw, the yield will be lower on straw than bran supplemented sawdust. To grow on wheat straw, it is recommended to mix the straw with about 10% sawdust and 10% grain spawn. Therefore, for a 10kg straw bag, we would use 1kg sawdust and 1kg grain spawn.

Its fairly aggressive nature makes it a fast substrate colonizer. The king oyster mushroom is one of the most tasty, if not the most tasty, oyster mushroom. Its nutritional content is expected to be similar or exceeding that of Pleurotus Ostreatus.

The king oyster, like any other oyster, has a meaty texture and strong nutty/earthy flavor, but this mushroom is superior to Pleurotus Pulmonarius and Pleurotus Ostreatus. This is the most delicious oyster mushroom, and it can be used in multitude of recipes. It is a very popular mushroom on the grill. This is one mushroom that does very well in the fridge since it can be kept in the cold for about two weeks.

The king oyster has about 90% biological efficiency, which makes it a very interesting mushroom to grow, but this is true on supplemented sawdust. On straw, the biological efficiency is close to half of what you can expect on sawdust. Nonetheless, supplemented straw substrate can produce some interesting results and large mushrooms. The stage at which mushrooms are harvested will affect biological efficiency. The larger the mushrooms get, the larger the biological efficiency but less desirable the mushrooms will be. Like most things, it’s a matter of keeping a balance between quality and biological efficiency.

A disadvantage of the king oyster, unlike Pleurotus Ostreatus or Pleurotus Plumonarius, is that it will not do well on just about any substrate. This is one mushroom that requires hardwood sawdust supplemented with bran in order to achieve some interesting biological efficiency.

Another disadvantage could be the extra step that some cultivators go through. This step is to use a layer of casing which consists of 50/50 peat moss and vermiculite with 1% hydrated lime. This allows to keep humidity on the top of the substrate or block and reduce contamination. However, this is not a must do step in order to produce king oyster mushrooms. The layer of casing on top helps the mycelium block to retain humidity on top and this helps with pinning on the top of the block. Otherwise, without the casing layer, the mycelium block will pin all over the bag including at the bottom of the bag forcing the hobbyist to remove the plastic bag. We don’t feel that using the casing as a hobbyist is a required step, but perhaps as a mass producer of king oyster mushrooms it is worth exploring.

One major advantage over other Pleurotus mushrooms is that the king oyster with the small cap will release much less spores in the air. Another advantage is that in order to accomplish the much sought after form of the king oyster, all one has to do is the opposite of the blue oyster mushroom. While the blue oyster requires tons of fresh air and humidity, the king oyster requires decent amounts of humidity and fresh air. It is that exposure to higher levels of CO2 and low levels of light that gives the king oyster a thick stem and small cap.

Exposing the king oyster to a lot of fresh air exchange will give it small stem and large cap, just like in nature.

Supplemented HWFP (hard wood fuel pellets) with a mix of 15% bran and small amounts of lime and gypsum is one of the best substrates to grow king oyster mushrooms. King oyster mycelium just can’t get enough of hardwood sawdust.

Hobbyists should expect multiple flushes on supplemented sawdust and expect fruit formation within three to four weeks after inoculation.

The ideal fruiting container for supplemented sawdust is polypropylene mushroom bags that you can find in our shop section. These bags can go in the pressure cooker and are a must for supplemented sawdust substrate, because this substrate must be sterilized. In addition, mushroom bags come with a filter patch that allows for air exchange to happen, which is very important for mycelium growth, especially with a dense substrate like sawdust. Without a filter patch, mycelium growth will come to a full stop.

For straw, the hobbyist can use polypropylene mushroom bags also, but the cheaper method is polyethylene bags that you can find in our shop section. Polypropylene bag will not go in the pressure cooker, because they will melt. This bag does not come with a filter patch and requires the hobbyist to make small holes in the bag for air exchange.

We do not recommend growing king oysters on straw because of the lower biological efficiency. If sawdust is available to you, then you should be using sawdust. If sawdust is not available to you, or if you simply want to experiment, then you can always grow king oyster mushrooms on supplemented wheat straw.

The growing parameters for the king oyster mushroom are interesting because they are not very demanding. Its biological efficiency is around 100% to 150% which is very interesting for a grower.

Incubation: Pinning: Fruiting:
Temperature: 19°C to 26°C Temperature: 10°C to 15°C Temperature: 15°C to 21°C
Humidity: 90% to 95% Humidity: 90% to 95% Humidity: 85% to 90%
Fresh air exchange: 1 per hour Fresh air exchange: 4-8 per hour Fresh air exchange: 4-5 per hour
Duration: 12 to 16 days Duration: 4 to 5 days Duration: 4 to 8 days
Luminosity: 500 lux to 1000 lux Luminosity: 500 lux to 1000 lux

When growing king oysters, the hobbyist has to pay very close attention to water droplet formation on the fruit body. Excessive moisture on king oysters will result in a formation of blotch, which is a bacterial disease that can be propagated to other king oyster mushrooms.

Keeping parameters in check and making sure there is no excessive humidity will reward the hobbyist with very delicious mushrooms.

Too much fresh air exchange will result in thin stem and large cap king oyster, just like in nature. Less air exchange and less light will result in fat stems and smaller caps.

In our shop section you can find king oyster related products such as liquid culture, Petri dishes, grain spawn and  sawdust spawn, as well as the occasional kits ready to fruit. 

Please see our other blogs covering more specific subjects about the fun world of growing mushrooms.