Edible
Oyster Mushroom
Pleurotus ostreatus
The common oyster grows in overlapping shelves on wood, with large caps and little or no stem.
King Oyster
Pleurotus eryngii
Edible
Also called king trumpet, french horn mushroom.
The king oyster is the largest oyster mushroom, known in North America as a cultivated grocery mushroom with a thick white stem and a small brown cap. In the wild it grows on the roots of sea holly and related plants in Mediterranean grasslands, and it is not native to North America.
The tell
Thick white stem, much larger than its small brown cap, with gills running down the stem.
Field marks
What to look at
Cap, underside and stem show in a photo. The spore print does not, and it is often the deciding check.
- Cap
- Convex to flat or slightly funnel-shaped, tan to grayish brown and smooth. Cultivated caps are small in relation to the stem.
- Underside
- True gills, white to cream, running down the stem.
- Stem
- Thick, firm and white, central or off-center; in cultivated mushrooms it is the largest part. No ring.
- Flesh
- White, dense and firm. Smell is mild.
- Spore print
- White.
- Size
- Cap 1 to 5 inches wide (2.5 to 13 cm); stem 2 to 6 inches long (5 to 15 cm).
Where and when
Where and when it grows
- Habitat
- In its native range, open grasslands and scrub. In North America it is known from commercial cultivation.
- Grows on
- In the wild, the roots of Eryngium plants and related members of the carrot family; in cultivation, sawdust and grain.
- Season
- Available year-round as a cultivated mushroom.
- Range
- Native to Europe, North Africa and parts of Asia; it is not treated as a wild species in standard North American field guides.
Lookalikes
What the king oyster gets confused with
Each card says how to tell the two apart.
Edibility
What the field guides say
Edible
The king oyster is grown commercially and sold as an edible mushroom across North America. North American field guides cover it little, because it is not a wild species here.
This page states what field guides record. It is not advice to eat, taste or handle anything, and a photo cannot settle edibility. If someone has eaten a wild mushroom that may be toxic, call poison control (1-800-222-1222 in the US) right away, before symptoms start: the deadliest species act hours later.
FAQ
Questions about the king oyster
What is a king oyster mushroom?
Pleurotus eryngii, the largest species of oyster mushroom. In North American stores it is sold as a thick white stem with a small brown cap, and it is grown on sawdust and grain.
Do king oyster mushrooms grow wild in North America?
Standard North American field guides do not treat it as a wild species. It is native to Mediterranean Europe, North Africa and parts of Asia, where it grows on the roots of sea holly and related plants.
How is a king oyster different from an oyster mushroom?
Both are Pleurotus species with gills that run down the stem. The king oyster has a thick, fleshy central stem and a small cap, while the common oyster grows in shelves on wood with large caps and little or no stem.
Sources
Where these facts come from
- Pleurotus eryngii
Naturalis Biodiversity Center
- The king oyster mushroom Pleurotus eryngii behaves as a necrotrophic pathogen of Eryngium campestre
Italian Journal of Mycology
- Pleurotus eryngii
Index Fungorum
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