Introduction to King Oyster ( King Trumpet Mushrooms)

When it comes to learning to Grow King Oyster Mushrooms, no previous experience or skill is needed. Infact they are the perfect beginner mushroom to grown, only slightly more difficult than the more commonly known oyster mushroom. They can be readily grow in bags bottles or logs- however they will take on a different appearance to the supermarket variety when grown on logs.

grow king oyster mushrooms

Key facts

  • Agar/Liquid Culture to Grain – 3 weeks
  • Grain to Grain/Hardwood Substrate – 3 weeks
  • Fruiting Chamber to 1st Flush – 1 week
  • 1st Flush to 2nd Flush – 2/3 weeks (maintain high humidity)
  • Spawn Run – 10 – 25 degrees Celsius
  • Fruiting Conditions – 7 – 20 degrees Celsius
  • Humidity above 80% 


Grains, especially Rye. Can also use millet, or wild bird seed. Hardwood sawdust is also an effective spawn medium.


King oyster mushrooms are often found growing wild on dead and decaying hardwood. However, unlike the other oyster species P. eryngii can be mildly parasitic of the roots of herbaceus plants.

In terms of mushroom cultivation the king oyster mushroom can be cultivated on cellulose rich substrates like sugar cane mulch, straw and corn cob however it will perform better yielding more and higher quality fruits when grown on hardwood or a supplemented hardwood mix like masters’ mix.

Supplement with wheat bran at 10-15%. King Oysters will also grow well on straw, however, unlike other Oyster species, the yield will be reduced.


Incubate the grain spawn at room temperature (20-22 deg C) until full colonization. Should take 10-14 days for full colonization.

Casing Layer: Unlike other Oyster mushrooms, the King Oyster will benefit from a casing layer. Use 50/50 peat moss and vermiculite with 1% hydrated lime to prevent casing contamination.


Expose fruiting container to lower temperatures (15 deg) and high humidity (95-100% RH). Increase fresh air.

Due to the top-fruiting nature of this species, the top can of the bag can be removed without need to fold back the plastic bag. This will create a reservoir which will retain CO2.

This species will produce thick meaty stems when grown in higher levels of CO2. The bag can be kept sealed until pins begin forming, making it one of the easiest mushrooms to fruit.

A casing layer is applied to the fully colonised surface of some mushroom species to increase humidity, improve yield and quality of the fruiting bodies.

When cultivating king oyster mushrooms a casing layer is completely optional. There is a slight risk of contamination when applying a casing layer. As an alternative we recommend to lightly scratch the top surface of the grow kit. Without opening the bag use your fingers or the handle of a spoon to scratch against the surface. This will create indentations which will generate the ideal conditions for the formation of king oyster mushroom primordia (pins).

For those who wish to apply a casing layer we recommend to use a mixture of 50% coco-coir and 50% vermiculite with 1% hydrated lime which is rehydrated with boiling water. Once cooled to room temperature a layer can be applied to the fully colonised surface of the substrate. 

Fruiting Containers: Large gusseted autoclavable grow bags with a filter patch will produce the best results. For straw logs use poly tubing. Can also be grown with success outdoors in garden beds.


Yield: Typically, 1 lb can be grown from a 5 lb supplemented sawdust block on the first flush. Multiple flushes can be achieved. Some cultivators get 2 lbs from a block on a single flush.

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