King Oyster Fruiting Conditions (Temperature & Humidity)

The King Oyster mushroom is a perfect candidate for cultivation, especially for beginners in farming, because it is easy to grow, grows quickly, and produces large fruiting bodies. If you want to give king oyster mushrooms a try, this article will let you know the ideal temperature and humidity to set the fruiting conditions for these mushrooms.

The ideal temperature to encourage king oyster mushrooms to fruit is 59°F–65°F (15°C–18°C). This temperature range is optimal for balancing warmth and moisture to allow the development of the fruiting bodies. The relative humidity must be between 85 and 95% during this stage to prevent the fruits from drying out.

While temperature and humidity play vital roles in the development of the fruiting bodies of king oysters, there are other conditions that must be met to get high-quality king oyster mushrooms. You will know more about these ideal conditions as you read below.


  • The ideal fruiting temperature for king oyster mushrooms is 59°F to 65°F, and the ideal fruiting humidity is between 85 and 95 percent relative humidity.
  • Aside from temperature and humidity, other fruiting conditions that must be set right to succeed in growing king oyster mushrooms are a fresh air exchange rate of 5 to 10 air exchanges per hour, a CO2 level of 1,000 to 1,500 ppm, and artificial light exposure of 12 to 16 hours per day.
  • The growth timeline of king oyster mushrooms lasts for 20–29 days from spawning to the fruiting stage.

The Optimal Temperature and Humidity for King Oysters to Fruit

King oyster mushrooms, the largest type of oyster mushrooms, can grow in just 3–4 weeks as they are vigorous growers. Their growing stage is divided into the spawn run or colonization stage, primordial or pinhead formation stage, fruiting stage, and flushing stage.

The growing process of king oyster mushrooms from spawning to the fruiting stage takes 20–29 days. Below is a table that summarizes their growing timeline.

Growth Stage Ideal Temperature Humidity C02 Level Duration
Spawn run/Colonization 24°C 90–95% 5,000–20,000 ppm 12–16 days
Pinhead Formation 12–16°C 95–100% 500–1,000 ppm 4–5 days
Fruiting Stage 15°C–18°C 85–95% <2,000 ppm 4–8 days

Oyster mushrooms have a growing time of about 2–8 weeks, depending on factors such as species, substrate, and lack or abundance of ideal growing conditions. Although fast-growing, they undergo the same stages when growing as any other mushroom species.

The first few stages of growing oyster mushrooms are dedicated to strain selection, substrate preparation, and inoculation. The actual growing timeline begins during incubation, followed by pinning, and finally, fruiting and harvesting. Each stage of development is important as it influences the speed and quality of the mushrooms being produced.

Each of the stages requires optimal conditions and takes a few days to accomplish. It is important to discuss each growth stage of the king oyster before we reach the fruiting stage. Below are the growth stages of king oysters after inoculation.

Spawn run or colonization stage of King Oysters

This stage allows the inoculated mushroom to be incubated at room temperature (75°F or 24°C). This takes 12–16 days, with the relative humidity level kept high at 90–95% and a CO2-rich environment of about 5,000–20,000 ppm.

Light is not necessary during this stage. You will know that your king oysters have successfully spawned when the grow kit bag is already covered with white mycelium.

Primordial or pinhead formation stage of King Oysters

This stage initiates the formation of mushrooms through pinning. This process only takes 4–5 days. Since king oysters love colder temperatures, the ideal temperature range during this stage is 12 to 16°C with an increased relative humidity of about 95–100%. The CO2 amount must be lowered to 500–1,000 ppm.

If the above conditions are met, you will be able to see a pinlike formation of the mycelium, which will all soon grow into mushrooms.

Fruiting stage of King Oysters

When encouraging the fruiting of your king oyster growing kit, you can do any of the following:

  • Poke 1/8 inch holes in the Humidity Dome zone, 1 inch above the top, and 1 inch between holes all the way around the package
  • Cut small ¼ inch X’s on any lumps or growths and side fruit the mushrooms.
  • Cut the Top of the bag by the Red Line and Roll down the bag
  • Remove the entire block if you have a fruiting chamber

During this stage, the temperature must be between 59°F and 65°F (15°C and 18°C) with a relative humidity of 85-95%. CO2 level must be less than 2,000 ppm. This process takes 4–8 days to complete.

Flushing stage of King Oysters

This stage refers to the harvesting stage. You can harvest 2 batches of crops from your king oyster mushrooms in a span of 45 days. To renew your block and prepare for the next flush harvest, submerge the wooden block for 3 to 5 hours in clean water.

This process helps rehydrate the wooden substrate and provide the mycelium with enough moisture. After rehydrating, place the mycelium block back into a clean bag and close it off to allow the mycelium time to regenerate. Monitor carefully for pin formation or signs of contamination.

Importance of Setting the Correct Fruiting Conditions for King Oysters

Healthy and normal king oyster mushrooms are commonly identified with a thick, meaty white stem and a small tan cap. If your aim is to produce quality king oyster mushrooms, you must set the ideal fruiting conditions when growing these mushrooms.

  • For the temperature, the ideal fruiting temperature is said to be between 59°F and 65°F (15°C and 18°C). This range is enough to balance between warmth and moisture which encourages the growth of mycelium, and therefore, insinuates fruiting.

Anything higher or lower than these numbers may inhibit the growth of your mushrooms.

  • The humidity level that must be maintained to allow fruiting in king oyster mushrooms is between 85 – 95%. You can do this by installing a humidifier to add moisture.

Low humidity levels can dry out the mushrooms and cause changes in texture and color. High humidity also encourages the growth of mushroom mycelium.

  • The optimal level of carbon dioxide (CO2) to induce fruiting in king oyster mushrooms is less than 2,000 ppm, which is ideally around 1,000 – 1,500 ppm. Carbon dioxide is necessary for mycelium growth and for the development of fruiting bodies. High levels of CO2 can negatively affect the development of your mushrooms.

  • Fresh air exchange rate for king oyster mushrooms must be between 5-10 air changes per hour. Fresh air exchange is necessary to avoid the build-up of harmful gases and to regulate the growing environment.

To promote proper air circulation, use fans or other ventilation systems to grow healthy fruits of king oysters.

  • King oysters do not need direct sunlight exposure but can benefit from artificial light exposure to regulate the mushroom's circadian rhythm and signal to fruit.

The ideal lighting conditions for king oyster mushrooms include light exposure of 12-16 hours per day, using fluorescent or LED lights. Insufficient lighting may cause thin and elongated growths instead of thick stems.

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