How to Cultivate King Trumpet Oyster Mushrooms at Home
Grow King Trumpet Oysters, Syringe to Harvest
Thick, meaty, savory fruits that shine in any hearty meal — here's the full walkthrough, from grain to harvest.
The mighty King Trumpet Oysters (a.k.a. King Oysters, French Horn, Trumpet Royale) win every hearty meal with robust, thick fruits. They bring a rich, savory flavor to any dish — or you can simply sauté them alone for a snack.
King Oysters (Pleurotus eryngii) enjoy cooler climates, making them a wonderful mushroom to cultivate indoors — especially in an area around 60°F — or during the fall season. Let's talk all about cultivating this easy gourmet mushroom at home!
You'll Need a Living Culture
This guide starts from a King Trumpet Oyster liquid culture. Grab yours below — and if you're new to liquid cultures, our LC guide covers the syringe basics first.
Shop King Trumpet Liquid Culture → How to Use a Liquid Culture →Shop Cultures & Supplies
Drag or scroll to explore →
1What Grains Should I Use?
King Oysters perform best on rye berries or a 5-grain mix. They also colonize well on oats — just be mindful of preparation and hydration. Straw is not a good starter for King Oysters when you're beginning on grain.
Pro Tip
- ALWAYS use properly sterilized grain. King Trumpets can be a little slower than common oysters and are more prone to bacterial issues if grain isn't clean.
- Trusted pre-sterilized grain bags/jars from companies like MidwestGrowKits.com or MycoLabs.com are a great choice.
- You can also sterilize your own grains at home — just cook them for the appropriate times based on your ratio and grain type.
2How Do I Inoculate?
This is a super easy part of cultivating King Oysters. We recommend a still-air box (SAB), a laminar flow hood, or the oven-door method. You'll want isopropyl alcohol, paper towels, vinyl gloves, grain bags/jars, and your King Oyster liquid culture syringe.
Be sure to check how many cc's to inject into your grain based on the jar/bag you're using.
- Put on vinyl gloves and clean your workspace thoroughly with 70% isopropyl alcohol. When finished, wipe/spray your gloves and let everything dry.
- Use the provided alcohol swabs to wipe down the injection port at the bottom of your grain bags or on top of your grain jar lid.
- Shake your syringe vigorously to distribute the mycelium evenly throughout the solution.
- Remove the cap from your King Trumpet liquid culture syringe and attach the provided sterile needle — now you're ready to inject.
Pro Tip
After puncturing the injection port, hold your syringe at a 45° angle and carefully give the bag/jar a full 360° spin. This helps spread the liquid culture across more grains.
You can also shake grain jars vigorously after inoculation — this won't harm the liquid culture and helps colonization begin more evenly.
3Colonization
King Trumpet is a cool-loving species. Optimal colonization is around 70–75°F, but they can still colonize down to 60°F (just slower). Above 80°F dramatically increases contamination risk and can stall growth.
Full colonization usually takes 14–21 days — a bit slower than common blue or pink oysters, but well worth the wait.
Grain bags: cut the tape holding the top and let the bag stand tall. Do a break-and-shake once at about 40–50% colonization to speed things up. Jars: simply shake the jar vigorously.
Keep bags/jars in complete darkness until fully colonized. Brief light exposure for observations won't harm or stall the mycelium.
If your mycelium is stalling, check your temperatures. Big fluctuations can throw off growth — but don't fret, daily observations help you catch issues early and correct them.
4Transferring to Substrate
King Oysters work best in a mixture of hardwood sawdust and soy hull — this combination is typically called Master's Mix.
RULE OF THUMB — one colonized grain bag can be split among 6 bags of Master's Mix. For quicker colonization, split between only 2.
King Trumpets do not benefit from a monotub bulk grow — they need specific fruiting zones. Keep them in bags and control where they fruit.
- Put on vinyl gloves and spray down your workspace with isopropyl alcohol. Spray the outside of your colonized grain bags/jars and the Master's Mix bag, then let dry.
- Cut the top of your colonized grain bag and the Master's Mix bag. Pour colonized grain into the Master's Mix bag.
- Seal the bag at the top (heat seal, clips, rubber bands, or zip ties). Leave some air inside so you can shake effectively.
- Shake the bag vigorously to disperse colonized grains throughout the substrate.
- Tape the top of your bag down to the bottom to lock in CO₂ buildup.
- At about 50% mycelium coverage, remove the tape, break down the block, and shake vigorously again to redistribute.
- Place back into block form and tape the top down to the bottom again.
- Let it fully colonize — then you're ready for the King Trumpet fruiting stage!
No fresh-air exchange right now — this mushroom still needs CO₂ to colonize again.
5The Fruiting Stage
This is where the magic happens! Give yourself a pat on the back for making it this far — just a few more easy steps to get this cake to fruit.
King Trumpet Oysters enjoy cooler climates during fruiting. You can go as low as 55–65°F and this mushroom will thrive. If you didn't keep it cool during colonization, now's the time — depending on the season, place it in a garage, a sunroom with cooler ambient temps, or even a cold basement.
For any method below, the following applies:
- 8–12 hours of light per day. Sunlight isn't necessary indoors; LED or overhead light helps with directional growth.
- Mist once daily. If your environment is dry, you may need to mist 2–3 times daily.
- Using a humidifier? You won't need to mist as often — aim for 80%+ humidity.
- Moderate fresh air exchange. King Oysters benefit from both CO₂ and oxygen.
- After your first flush, rehydrate the block by dunking in water for 18–24 hours. Don't exceed 24 hours.
- Later flushes may be smaller than the first — that's normal.
Where to fruit from: either cut across the top of your bag to remove the top completely (top-fruiting), or cut a "window" on the front of your bag to fruit from there.
Method 1 — Fruiting Chamber (Monotub / Tote)
- Use a monotub, tote, or enclosed space where you can introduce humidity, light, and oxygen.
- King Oysters fruit well in bags inside a humidity-controlled chamber.
- Using a monotub? Apply filter patches on the holes to support fresh air exchange.
- No holes? Open the lid for a few minutes 2–3 times a day to release CO₂ and introduce fresh air.
Method 2 — Automated Grow Tent
- Place fully colonized blocks into an automated grow tent if you already have one. No need to buy one solely for King Oysters, but it's a great tool for optimizing fruiting if available.
- Promote fresh air exchange by opening the tent door periodically, or connect a fan that draws outside air into the tent.
- Automate a fan with a timer (example: 15 minutes every 3–4 hours) and adjust based on observations.
- Because King Oysters also benefit from CO₂, consider placing bags lower in the tent — CO₂ is heavier and collects near the bottom.
- Aim for 80%+ humidity and avoid prolonged temps above 80°F.
You won't need to worry much about contamination in this stage unless your cakes go above 80°F for prolonged periods, or you leave stagnant water at the bottom of your bags for days.
It's normal for water/yellow liquid to collect at the bottom of your bag — just dump out excess buildup whenever you notice it.
Need Help or Have Questions?
If you have specific questions along the way, contact us via email or phone. We're here for you every step of the way.
Best of luck with everything, fellow fungi friends — and happy cultivating!
Spore Genetics — Exceptional Mushroom Spores & Cultures