Meet the Black Pearl King
The Black Pearl King Oyster (Pleurotus ostreatus × Pleurotus eryngii) is one of the most fascinating hybrids in the gourmet mushroom world.
Bred originally in Asia, this cross between the classic King Oyster and the vigorous Japanese Oyster combines the best of both:
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Thick, meaty stems that cook like scallops or steak
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Silky gray-black caps with beautiful rippling edges
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Fast colonization and reliable fruiting in indoor and tunnel environments
At Hernshaw Farms, we cultivate our Black Pearls inside the historic Memorial Tunnel along the West Virginia Turnpike, where the consistent underground climate is perfect for controlled-environment mushrooms. You can experience the same magic at home with our Black Pearl King Oyster Grow Kit — a ready-to-fruit block made with Appalachian-grown substrate and mycelium.
The Flavor and Texture
Black Pearls are prized by chefs for their dense, chewy texture and rich umami flavor. When sliced and pan-seared, the stems develop a buttery crust similar to sea scallops.
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Flavor: Savory, nutty, slightly earthy
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Texture: Firm and meaty — ideal for grilling or sautéing
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Color: Slate gray to dark umber caps with white stalks
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Yield: 1–2 flushes per kit with proper humidity and airflow
They’re versatile enough for vegan steaks, ramen, stir-fries, risottos, and skewers, and they hold their shape beautifully when roasted or smoked.
Growing Black Pearls: What Makes Them Special
Unlike delicate mushrooms, Black Pearl Kings are robust and forgiving — but their appearance and yield depend heavily on CO₂ levels, humidity, and light exposure.
Temperature and Humidity
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Temperature range: 60–72°F (16–22°C)
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Humidity: 85–95% during pinning, 80–90% during fruiting
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Light: Bright, indirect natural or artificial light
Black Pearls do best when they think they’re growing in a forest after rainfall: cool, humid, and well-ventilated.
CO₂ Levels: The Key to Shape and Size
The shape of your Black Pearl Kings will tell you everything about their environment.
🌫️ High CO₂ (Low Airflow) Conditions
If you grow them in a still environment or without much air exchange:
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Stems grow tall and thick, almost column-like.
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Caps remain small and tight, with minimal flattening.
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Texture becomes extra dense — great for slicing as “vegan scallops.”
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Ideal for colder rooms or when you want longer stems.
💡 Tip: Keep the bag partially sealed or use a humidity tote with small ventilation holes for this form.
🌬️ Low CO₂ (High Airflow) Conditions
If you increase air exchange and light exposure:
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Caps spread wide into classic oyster shapes.
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Stems stay shorter and softer.
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The mushrooms resemble smooth fans or “gray trumpets.”
💡 Tip: Cut a larger slit or open the top of the bag completely once pins form; mist 1–2× daily to prevent drying.
Both styles are equally delicious — it just depends on your aesthetic and airflow setup.
How to Grow Black Pearls from the Hernshaw Farms Kit
Your Black Pearl King Oyster Grow Kit comes fully colonized and ready to fruit.
Step-by-Step
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Unbox and Inspect: Your block should be firm and mostly white.
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Don’t open yet! Place the kit in bright, indirect light at 60–70°F for a few days to acclimate.
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Watch for pinning: When you see small gray knots under the plastic, it’s time to choose your airflow setup.
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Slit or open the bag:
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For tall stems (high CO₂), make a small slit.
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For wide caps (low CO₂), open across the top like a chip bag.
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Mist daily: Use clean water, never soak.
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Harvest: Twist and pull gently before caps flatten completely.
Your block can rest 10–14 days after the first flush, then be rehydrated for a second harvest.
Common Growth Patterns
| Condition | Result | Appearance | Notes |
|---|---|---|---|
| High CO₂ | Tall stems | Thick, club-shaped fruit | Great texture for slicing |
| Low CO₂ | Wide caps | Classic oyster form | Excellent for pan-frying |
| Too dry | Wrinkled caps | Pale and cracked | Increase misting |
| Too dark | Long stems | Small caps | Move to brighter spot |
Cooking the Black Pearl King Oyster
Once harvested, the real fun begins.
🍳 Pan-Seared “Scallops”
Slice stems into thick rounds. Sear in olive oil or butter until golden on each side. Deglaze with soy sauce and a squeeze of lemon.
🍜 Ramen Topping
Slice lengthwise into strips and pan-fry with sesame oil, garlic, and ginger.
🍢 Grilled Skewers
Cube the stems, brush with teriyaki glaze, and grill until charred.
🍝 Creamy Pasta or Risotto
Their dense texture holds up beautifully to rich sauces — toss into Alfredo or miso cream.
🧄 Flavor Boosting Tips
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Sauté slowly for maximum umami.
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Add a splash of white wine or tamari near the end.
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Save stems for stocks and broths.
Storage and Preservation
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Refrigerate in a paper bag up to 7 days.
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Freeze sautéed mushrooms for up to 3 months.
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Dry slices for shelf-stable storage — rehydrate before cooking.
Nutritional Benefits
Black Pearl Kings are rich in:
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Plant protein & fiber
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B vitamins (niacin, riboflavin)
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Potassium and selenium
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Antioxidants and ergothioneine
Their combination of nutrition and texture makes them one of the most satisfying meat alternatives in the mushroom world.
Why We Love Growing Them
In the Memorial Tunnel on the West Virginia Turnpike, Hernshaw Farms grows thousands of Black Pearl blocks each month. The constant 60°F air, natural humidity, and stable CO₂ levels allow us to replicate ideal conditions year-round.
It’s part of our Appalachian mission to transform historic infrastructure into sustainable agriculture — creating jobs, supporting small farms, and bringing gourmet mushrooms to tables across America.
You can join that story by starting your own harvest at home.
🛒 Shop the Kit
👉 Black Pearl King Oyster Grow Kit — ready to fruit, shipped fresh from the Memorial Tunnel.
