Growing King Oyster Mushrooms

Pleurotus Eryngii

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What Are King Oyster Mushrooms?

The king oyster or trumpet mushroom belongs to the oyster mushroom genus, pleurotus. It’s the largest oyster mushroom featuring a thick and meaty stem (stipe) which has resulted in it being valued for culinary purposes around the world.

The king oyster is purposefully grown with elevated levels of CO2 to encourage the typical king oyster shape with a large stem and small cap.

The king oyster is a ‘top-fruiting’ species as opposed to the pink, white and yellow oyster species which fruit well from the side. 


What Do King Oyster Mushrooms Taste Like?

King oyster mushrooms are thick and meaty with a mild mushroom flavour which sweetens upon cooking. It holds together well during cooking and if often used as a substitute for scallops or other mild flavour meats.

King oyster mushrooms are some of my favourite for cooking with. Either fried, grilled or even in soups. You haven’t lived until you’ve tried some crumbed king oyster mushrooms. 

What Do King Oyster Mushrooms Grow On?

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.

It can be grown in outdoor garden beds, monotubs or mushroom grow bags during the cooler months of the year.

Grow King Oysters Without A Pressure Cooker

Learn how to grow king oyster mushrooms on a supplemented hardwood substrate without needing any extra equipment.

Learn How To Grow King Oysters

Opening A King Oyster Grow Kit

A different approach can be taken when opening a king oyster mushroom grow kit or fruiting block. 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.

King oyster grow kit with optional casing layer.

What Is A Casing Layer?

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. 

Learn How To Make A
Casing Layer

Using A Humidifier

Humidity can be managed through a diligent misting and fanning regime, however the introduction of a humidifier and humidity controller can help automate the process and ensure consistency.

Adding a 6L humidifier and controller to a greenhouse with the addition of a USB fan is a quick and easy way to make a low cost fruiting chamber that delivers excellent results.

SGFC Shotgun Fruiting Chamber

Making A Fruiting Chamber

Mushrooms require humidity to grow. We recommend using a mini-greenhouse. Spraying the inside walls of the greenhouse will help raise humidity. A cheap humidifier can be used to automate the process.

It’s important to ensure that the grow kit has fresh air exchange. Mushrooms produce carbon dioxide and will grow long and leggy in search of more oxygen. 

Check the product pages for species specific requirements.

Alternatively you can build a Shotgun Fruiting Chamber (SGFC) from a few common items found easily in your local hardware store.

King Oyster Mushroom Spawn Run

Despite king oyster mushrooms being vigorous, they can be expected to take 1 further week to fully colonise and prepare for fruiting.

Abundant king oyster primordia formed within the sealed grow bag.
King oyster primordia trapped within the grow bag.

King Oyster Mushroom
Pinning Conditions

The bag may be kept closed until primordia has formed. This will ensure that the substrate remains in a high humidity environment which often results in the largest pin sets.

Keep at temperatures below 15 degrees Celsius (60f) to trigger pinning. Keep humidity over 80% with slightly increased fresh air for the development of primordia.

If using a mushroom grow bag, only the top of the bag needs to be removed. The higher sides will allow for CO2 to pool and develop thicker fruiting bodies with small caps.

Sometimes primordia will form in the humid space between the bag and the grow kit. Taping the sides of the bag firmly to reduce air movement around the base of the block will reduce the formation of undesired primordia. Alternatively, a cut can be made to release these pins to complete growth.

King Oyster Mushroom Fruiting Conditions

Maintain the mushrooms at temperatures between 15 – 20 degrees Celsius (59 – 68f) for fruiting body development. Humidity may be lowered but should remain above 80%RH

Watch Our King Oyster Grow Guide (Coming Soon)

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