Organic Black King Mushroom Fruiting Block

Easily harvest your own Black Pearl mushrooms, also known as Black Pearl oyster, Black King, or Shimofuri Hiratake. This Japanese variety in the oyster mushroom group is prized for its striking appearance, its meaty stems, and a texture halfway between a classic oyster mushroom and king oyster.

• Variety: Black King, Pleurotus spp., Black Pearl, Shimofuri Hiratake
• Yield: up to 1.5–2 kg (approx. 3.3–4.4 lb) of fresh mushrooms over 2 to 3 harvests
• Composition: water, wood sawdust, cereals, lime, and Black Pearl mycelium
• Net weight: approx. 4.8 kg (about 10.6 lb)
• Dimensions: approx. 25 x 20 x 20 cm (about 10 x 8 x 8 in)
• Uses: cooking, culinary processing, drying, or preserving
• Origin: Belgium ( La Mycosphère)

Note: yield figures are estimates based on our production experience. They are not guaranteed, as productivity depends heavily on growing conditions: temperature, humidity, ventilation, light, and the grower's experience.

🍄 The variety: Black King

The Black Pearl is a fairly recent variety, still uncommon in Europe. It's often described as a "UFO" in the world of oyster mushrooms: it grows in clusters like an oyster mushroom but develops wider, meatier stems reminiscent of king oyster.

Its caps are rounded, sometimes slightly marbled, with a color ranging from gray-brown to dark brown depending on temperature, humidity, and maturity. The cooler the conditions, the more pronounced the color contrasts can be.

In the kitchen, the Black Pearl offers a firm, tender, and juicy texture. Its stem is far more interesting than that of a classic oyster mushroom: it stays pleasant to cook and gives a nice bite. Its flavor is mild and umami, with a more "meaty" side than the gray oyster.

Our quality commitment

We produce our mycelium under laboratory conditions, ensuring varietal purity and optimal quality.

We produce our mycelium in a 100% organic way, and all our products are certified "BE-BIO-01, Agriculture Belgium" by CERTISYS.

📦 Using the fruiting block

If you can't use the block right away, keep it in the refrigerator for about 2 weeks. The Black Pearl prefers cool conditions, so it's easier to grow in autumn, winter, or spring. In summer, choose the coolest spot possible.

Unlike classic oyster mushrooms, we recommend growing the Black Pearl with top fruiting — that is, with an opening on the top of the block. This method encourages more vertical growth, meatier stems, and an appearance closer to king oyster.

1. Stand the block upright in a bright room, but out of direct sunlight.
2. Open the top of the bag above the substrate, without removing the plastic completely.
3. Fold the edges of the bag slightly outward to create a clean opening on top.
4. Keep the plastic around the block: it helps maintain humidity and limits drying of the substrate.
5. Keep the surface of the substrate slightly moist until the young mushrooms appear.
6. During growth, maintain high humidity, ideally between 85 and 95%.
7. Ventilate the room regularly: a lack of fresh air can cause overly long stems, deformed caps, or slower growth.

If the surrounding air is dry, you can place the block in a small greenhouse, a grow box, or a protected space like a mini fruiting chamber. The goal is to keep a humid atmosphere around the block without the mushrooms being constantly wet.

Use our minispray or our professional foggers to maintain enough humidity around the block.

⚙️ Growing parameters

Good to know: ventilation influences the shape of the mushrooms. With plenty of fresh air, the caps tend to open up more, like classic oyster mushrooms. With slightly more moderate ventilation, the stems often become thicker, with an appearance closer to king oyster. Be careful, though: too great a lack of air can cause elongated stems, deformed caps, or slower growth.

🌱 Where to grow it

The Black Pearl can be grown indoors: kitchen, cellar, garage, laundry room, or a cool room. It needs a little light to form well, but you should avoid direct sunlight, radiators, and dry drafts.

The goal is to keep the block moist without soaking it. The mushrooms like humidity, but a constantly wet surface can encourage bacteria or mold.

🔄 Harvesting

Harvest the clusters when the caps are still slightly domed or barely open, before the edges curl up sharply. At this stage, the texture is more tender, storage life is better, and the flavor is more refined.

To harvest, grasp the cluster at the base and gently twist it off. Remove any leftover pieces of stem on the substrate, then keep the block moist to prepare for the next harvest.

The first harvest is usually the most abundant. Later harvests are often smaller but can still produce fine mushrooms if the block stays well hydrated.

🍳 Cooking tips

The Black Pearl is cooked whole: caps and stems alike. Its meaty texture is ideal pan-fried, grilled, in a stir-fry, in pasta, a risotto, a soup, or a vegetarian recipe where you're looking for a firmer texture.

For a simple preparation: tear the clusters by hand, sauté them over medium-high heat with a little oil or butter, then add garlic, herbs, or sauce at the end of cooking. Like many oyster mushrooms, it develops its aromas better when well seared.

Legal notice for Belgium: "Organic growing substrate: pasteurized and inoculated mushroom-farm substrate" (Derogation No. EM470.J). Do not consume the substrate.