How to Grow King Oyster Mushrooms

The king oyster mushroom is a choice edible mushroom that is particularly popular for consumption in East Asia and parts of Europe. In the US, this mushroom is also steadily growing in popularity. Growing king oyster mushrooms at home is definitely achievable as long as you carefully follow guidelines for success.

In this guide, we’ll talk about the fungal classification of this delicious mushroom and explain the most achievable methods for growing king oyster mushrooms in a home setting.

Alright, let’s get to it!

King Oyster Mushrooms: Fungal Classification and a Brief Intro

As the common name suggests, the king oyster belongs to the oyster mushroom genus, Pleurotus. Its scientific name is Pleurotus eryngii. This species of oyster mushroom is native to North Africa, the Middle East, and the Mediterranean regions of Europe.

Pleurotus eryngii is weakly parasitic on the roots of herbaceous plants and it is saprotrophic, meaning it both preys on living plants and decomposes dead wood. By decomposing wood, the king oyster mushroom allows essential nutrients to return to the soil. As white-rot fungi, king oysters are able to break down all parts of wood, including lignin, cellulose, and hemicellulose. During this process, they take in carbon for food and cellular growth. This benefits the fungus and also aids in carbon sequestration, delaying the process of carbon returning to the atmosphere.

While most species in the Pleurotus genus are bracket-like fungi that have either a rudimentary stem (stipe in mycology terms) or none at all. The king oyster mushroom looks quite a bit different, although it can grow in clusters like other oysters.

This mushroom features a thick, elongated stipe. The brown cap is convex and the mushroom is typically harvested before the cap begins to flatten out. The grey-brown gills run decurrently down the upper portion of the stipe.

How to Grow King Oyster Mushrooms at Home

Like a number of species of wood-decaying mushrooms, you can grow king oysters at home so long as you provide an appropriate substrate and provide adequate growing conditions.

Below, we’ll cover in detail what these conditions are. It’s important to note that this species of oyster mushroom is more difficult to grow than the common oyster, Pleurotus ostreatus. You will need to take extra care when cultivating Pleurotus eryngii.

Why King Oysters Are a Bit Tricky

Most oyster mushrooms are easy to cultivate as they will grow in a wide range of cellulose-containing substrates. They’re also a great candidate for growing without having to sterilize substrate because they can readily colonize tough material, such as straw, faster than other microbial competitors.

King oyster mushrooms, however, are a bit trickier as their mycelium tends to be weaker and much slower than other Pleurotus species. Because of these factors, bulk-pasteurized substrates that cool in the open air are at a much higher risk of contamination by other fungi and bacteria. Instead, growers usually sterilize sealed grow bags or bottles, using self-healing ports to inoculate the containers.

Pasteurization involves processing a substrate to significantly reduce microbial life that would compete with the mycelium. Sterilizing a substrate completely eliminates all microbial life and spores from a substrate. This process gives your fungus the best chance of colonizing the substrate. Sterilizing can be more expensive and requires a much higher degree of sanitation.

Two Choices for Sterilized Substrate

While it is possible to sterilize your substrate at home, for beginner home-growers, we generally recommend two options to obtain a pre-sterilized substrate for growing Pleurotus eryngii. We’ll discuss these in-depth below.

Purchase a King Oyster Mushroom Growing Kit

One option, and the least involved, is to purchase a king oyster (or king trumpet) mushroom grow kit from various online mushroom supply and growing sites. For best results, you can also purchase a fruiting chamber. These kits will contain a fully mycelium-colonized substrate. The grow bag typically has a filter patch on it that allows air to travel into the bag. This prevents the entrance of microbial life, depending on the patch, down to between .2-5 microns in size. Instructions usually recommend initiating fruiting within 3 days of receiving the kit. To fruit, you simply follow the instructions that come with your kit.

Purchase Pre-Sterilized Substrate and Liquid Culture

Another option is to purchase a liquid culture and grow bags that aren’t inoculated but are filled with sterilized substrate. For king oysters, look for pre-sterilized grow bags that have a filter patch, and self-healing injection port, and are filled with a hardwood sawdust-based substrate.

This second option results in a faster colonization rate than if you were to directly inoculate the grow bag with the liquid culture. The downside to this method is that you will have to transfer the grain spawn into the sterilized bag. To reduce the risk of contamination from airborne microbes, you’ll need to transfer in a clean environment. This could either be a still airbox, in front of a flow hood that removes air microbes from the immediate vicinity, or in a closet-type space that isn’t connected to an HVAC system. Once transferred, you’ll want to break up and distribute the grain spawn throughout the substrate.

Incubation and Fruiting Requirements for King Oyster Mushrooms

Once you receive these items, you have two options. You can either directly inoculate the liquid culture through the injection port and let the spawn colonize the substrate. Or, you can inject the liquid culture into a spawn-growing grain jar, and then transfer the colonized grain into the sterilized substrate. You can purchase jars of sterilized rye berries from mushroom-growing companies. With this second option, you’re giving your spore culture a leg up by inoculating it into grain-like rye berries, which are much easier for the mycelium to initially colonize than hardwood sawdust.

Now that you have an idea of how to obtain a sterilized substrate, you’ll need to know this species’s growing requirements. Humidity, temperature and light are all very important. If you purchase a grow kit, you’ll generally only need to know its fruiting requirements. If you plan on growing your own spawn, you’ll also need to know the incubation requirements for Pleurotus eryngii.

Incubation Requirements

The incubation period refers to the time it takes for the mycelium to colonize a substrate. The timeline varies by species. For king oyster mushrooms, you can expect an incubation period of about 10-21 days for inoculating a spawn jar and about another 2-3 weeks to fully colonize a grow bag. If you’re one-shot inoculating a grow bag with spore culture, then expect at least 4-6 weeks before the bag is ready to fruit. After this phase is completed, the mycelium is ready to begin fruiting. The temperature range for incubation of Pleurotus eryngii is about 68-75 degrees Fahrenheit. Ideally, provide indirect light during this time, but light isn’t as important quite yet.

Fruiting Requirements

Once your grow bag is fully colonized by king oyster mycelium, it’s time to begin the fruiting process. To successfully trigger fruiting, the mycelium needs a change in atmospheric conditions which can include light, temperature, humidity, and airflow. To allow mushroom formation to begin, you’ll need to cut or open the grow bag and place it in ideal conditions. Typically, growers top-fruit king oysters, so you can cut a slit at the top of the bag, or reopen it if you rolled and taped the opening after spawn transfer. To trigger fruiting of king oyster mushrooms, provide the following conditions:

• temperatures between 53.6-62.6 degrees Fahrenheit (note the drop from incubation temps)
• humidity range of 80-95%
• 8-12 hours of indirect sunlight or comparable artificial lighting 
• Consistent fresh air exchange

Once these conditions trigger the mycelium to enter the fruiting stage, you can typically expect to see pin formation occur within 4-8 days. Repeated flushing isn’t as common with king oysters as it is with other species. This is due to their high humidity requirement to induce fruit formation as well as their increased susceptibility to developing brown blotch disease caused by the bacteria, Pseudomonas tolaasii. Trichoderma is also a bane to any mushroom growers existence. It is a prevalent green mold that notifies the cultivator that they were not clean and sterile in their prior work.

How to Achieve Required Conditions

Fruiting in a ventilated grow chamber is one of the best methods for consistently achieving the required growing conditions, especially for species with high humidity requirements. You can purchase climate-controlled growing chambers or tents, or you can use exterior sources to achieve the ideal conditions. If your fruiting container isn’t climate controlled, you have a few options to create the required conditions.

To achieve the ideal humidity range, you can use humidifiers, or use spray bottles to moisten the interior walls of a fruiting chamber or around the opening of a grow bag. To maintain the high humidity levels required for king oyster mushrooms, you should spray enough that you can consistently see condensation inside the grow bag. Be careful to not directly spray the fruiting mushrooms as this can lead to rot.

It’s also useful to think about how close you set the chamber or grow tent to windows. This is especially true in the summer when they can heat up your growing area.

An A/C unit placed next to the growing container can help you control the temperature. If you do place an A/C unit next to the grow chamber, you’ll need to keep a much closer eye on humidity and mist more frequently. Another solution is to place the growing chamber in a basement as long as it has a window for indirect lighting or if you set up an adequate artificial light source. Basements with a light source are often a good choice for species with cooler fruiting requirements because they are almost always cooler than the rest of an A/C-controlled house. If you do use artificial lighting, aim to provide 850-1500 lux.

Harvesting and Use of King Oyster Mushrooms

Your king oyster mushrooms are ready for harvesting when the stipes are thick and the brown convex caps are fully developed. For best results, harvest before the caps begin to flatten and expand outward. Remove the entirety of the mushrooms from the substrate. If you wish to attempt a second flush, make sure the grow block stays in the plastic bag, where it has the best chance of maintaining high humidity levels.

Due to their firmer structure, king oysters have a longer shelf life than most other oyster species. You can expect these mushrooms to stay fresh in a fridge for up to two weeks after harvesting.

You can prepare and cook them in a variety of ways and for a range of dishes. Of course, you can always opt for the tried and true, classic pan frying with butter, garlic, and sage. Another popular recipe for these meaty mushrooms is to grill them for kabobs with vegetables. Make sure to incorporate the stipes with king oyster meals as they have a great texture and are packed with flavor. Some people even use them as faux scallops as pictured below!

The photo featured at the top of this post is © Miriam Doerr Martin Frommherz/Shutterstock.com

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