All about The King Oyster Mushroom

The King Oyster Mushroom Pleurotus eryngii (De Candolle ex Fries) Quelet sensu lato

Introduction: 

Fig. 01: The King Oyster Mushroom

Pleurotus eryngii is by far the best-tasting Oyster mushroom, well deserving of the title, the King Pleurotus ostreatus and Pleurotus pulmonarius on this same material, at the same rate of spawning, unless supplements are added or a unique spawning method is employed.

Oyster. Popular in Europe, this stout, thickly flesh mushroom, is one of the largest species in the genus. Preferring hardwoods, this mushroom is easy to grow. Although this mushroom grows on the cereal (wheat) straws, the yields are not as substantial as that of

Common Names:

• The King Oyster
•  Boletus of the Steppes

Description:

Cap 3–12 cm in diameter, at first convex, expanding with age, becoming funnel-shaped, with the margin typically inrolled, extending with age. Stem 3–10 cm in length, central, thick, tapering downwards. Gills fairly distant, thin, grayish, and decurrent. Growing individually or in small groups. Cultivated mushrooms achieve a greater stature and overall size compared to ones collected in the wild.

Distribution:

Throughout southern Europe, North Africa, central Asia, and southern Russia.

Characteristic Features:

Natural Habitat:

 Terrestrial, growing on the buried roots of hardwoods. This mushroom is thought to a facultative parasite on dying Eryngium campestre, a member of the thistle family.

Microscopic Features: 

Spores white, ellipsoid, 10–14 × 4–5 µ. Clamp connections present. Context monomitic.

Available Strains: 

Most strains originate from Europe. Strains are commonly available from many culture libraries.

Mycelial Characteristics: 

Whitish, longitudinally radial at first, sometimes rhizomorphic, soon thickening and becoming cottony in age.

Fragrance Signature: 

Grain spawn and myceliated straw smells rich, sweet, and classically Oyster-esque but not anise-like.

Natural Method of Cultivation: 

Outdoors, on log sections turned vertically, and on stumps inoculated with plug spawn. This species is easily grown on straw outdoors using the mound method. Some strains are native to conifers (Abies spp.). If brought into culture, these races could help recycle conifer stumps throughout the world.

Recommended Courses for Expansion of Mycelial Mass to Achieve Fruiting: 

Traditional or liquid-inoculation of grain spawn to fruiting substrates, preferably sterilized sawdust. Pasteurized straw cultivation is comparatively less productive unless inoculated by the following method. We recommend inoculating wheat straw with equal quantities of sawdust and grain spawn. In other words, every ton of wheat straw (2,000 pounds dry weight) should simultaneously receive 100 pounds of grain spawn (wet weight) and 100 pounds of sawdust spawn (wet weight). This combination spawning method gives rise to large specimens on wheat straw.

Substrates for Fruiting: 

Most hardwoods, wheat straw, and cottonseed hulls support fruitings. This mushroom is not as adaptive as P. pulmonarius and P. ostreatus to a broad range of substrates. Nevertheless, many materials can be used. We have been pleased with its performance on recycled, resterilized waste Shiitake substrate. However, we would not recommend this approach for commercial purposes unless the preferred wood type or alternative substrate materials were exceedingly scarce and cost-prohibitive. If cultivating this mushroom on wheat straw, the addition of 5–10% cottonseed meal had the greatest effect in enhancing yield.

Recommended Containers for Fruiting: 

Trays, plastic bags, columns, and bottles.

Yield Potentials: 

1 pound of mushrooms per 5 pounds of sterilized sawdust/chips/bran, or approximately 90% biological efficiency. Wheat straw fruitings, from experts experience, have tallied approximately half of that from enriched sawdust. The stage at which the mushrooms are picked significantly affects yield efficiencies.

Fig. 02: Image showing the growth parameters for The King Oyster Mushroom Cultivation

Harvest Hints:

 This mushroom can become quite large if the substrate has a sufficient nutritional base. The stage at which the fruitbody should be picked depends largely upon the strain and the cultivator’s preference. We prefer harvesting the mushrooms just before the cap margin flattens out, when the cap margins are inrolled or deeply incurved, and the mushrooms are at an adolescent stage.

Form of Product Sold to Market:

 Mushrooms collected in the wild are sold in markets in Spain, Morocco, and other southern European countries.

Flavor, Preparation, and Cooking: 

Stir-frying until edges become crispy golden brown. A chewy, nutty mushroom, this species is far superior to P. ostreatus and P. pulmonarius. This mushroom, like other Oyster mushrooms, goes well with Italian dishes, and especially with lamb, pork, and fish.

Comments: 

The King Oyster’s stout form, short gills, and thick flesh, coupled with its pleasing flavor strongly commends this species among connoisseur growers and chefs. The short gills mean this mushroom releases comparatively fewer spores per pound of harvested mushrooms, a significant advantage over other Oyster species. Pleurotus eryngii has a better constitution than other Oyster species and, in many authors’ opinions, is the best flavored. Gary Lincoff (1990) reported that this mushroom received the highest acclamations of any of the mushrooms tasted during a culinary tour of mycophagists sampling the treasured mushrooms of Europe. This is the only Oyster species we know that ships well over long distances and has an extended shelf life.

Although other cultivators have recommended a casing layer, we have found its application unnecessary.  Our best fruitings of Pleurotus eryngii, in terms of both yields and quality, have been on 20% bran-enriched alder sawdust. Three weeks after inoculation with grain spawn, the fully colonized bags of sterilized sawdust/chips/bran are brought into the growing room. The tops of the bags are horizontally sliced opened, resulting in a 3- to 4-inch plastic wall around and above the surface plane of the mycelium. In effect, these sidewalls protect the supersensitive aerial mycelium from sudden dehydration. Condensation is promoted. Coupled with a descending fog environment within the growing room, the perfect microclimate for primordia formation is provided.

Zadrazil (1974) showed mycelial growth peaked when carbon dioxide levels approached 220,000 ppm or 22%. The stimulatory effect of CO2 on mycelial growth allows this mushroom to grow under conditions that would be stifling for most other mushrooms and lifeforms. Optimum pH levels at the time of spawning should be between 7.5 and 8.5. On wheat straw, the pH naturally declines to a range of 5.5 to 6.5, a range ideal for fruiting.

Published Date: August 26, 2019 
Topic:  The King Oyster  Mushroom
Subject: Mushroom Cultivation
References: Stamets P. Growing gourmet and medicinal mushroom, Ten Speed Press (2000) , eISBN: 978-1-60774-138-1, 2000,