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Hypsizygus ulmarius

[ Basidiomycetes > Agaricales > Tricholomataceae > Hypsizygus . . . ]

by Ron Meyers

One of my favorite table mushrooms is the Oyster Mushroom, Pleurotus ostreatus. I have been fortunate to harvest at least a meal from my yard almost every year. So when I saw a solitary mushroom growing from an injury in a box elder tree, I thought it was another oyster. But on closer inspection it was very different. First of all it was solitary. It had a nearly central stalk, bending from its attachment to the tree. And it grew slowly and changed little over a period of a week to ten days. I had found my first Hypsizygus ulmarius.

Since then I have had several fruit on other box elder trees in my yard. Usually they were solitary, but in one instance they were paired.

Hypsizygus ulmarius, sometimes called the "elm oyster," is edible, but in my opinion not nearly so palatable as the Pleurotus group. It is somewhat tougher and not likely to occur in large enough quantities for a really good meal.


Ecology: Saprobic; growing alone or in pairs (sometimes in clusters of three), usually growing from branch scar sites of living hardwoods, particularly elm or box elder; widespread at least though the eastern United States (Arora reports it from California); August to December.

Cap: 5-15 cm; convex with a slightly inrolled margin at first, becoming almost flat, with a slightly sunken center; white, turning to creamy buff or tan; cracking and forming small scales or patches.

Gills: Attached to the stem and not running down it; close or nearly distant; whitish, becoming cream.

Stem: 5-10 cm long, 1-2.5 cm thick; dry; smooth to hairy; whitish; solid; stout; off-center to nearly central; sometimes enlarged at base.

Flesh: Firm; white.

Taste: Mild; odor not distinctive.

Spore Print: White to buff.

Microscopic Features: Spores 5-6 µ; smooth; round or nearly so; inamyloid.

REFERENCES: (Bulliard, Fries) Redhead, 1986. (Redhead, 1986; Hoffman, Tiffany & Knaphus, 1989; Lincoff, 1992; Arora, 1986; Horn, Kay, and Abel, 1993; Bessette, Bessette & Fischer, 1997.) Herb. Kuo 09110403.

Hypsizygus ulmarius certainly must hold the record for being the most often misnamed mushroom in America. While it was formerly known as Pleurotus ulmarius, the most common error has been to use the name Hypsizygus tessulatus. A report by Scott Redhead in Mycologia (1986), however, indicates that Hypsizygus tessellatus is a smaller mushroom which usually grows in clusters, and is widely cultivated in Japan as hon-shimeji.


Hypsizygus ulmarius

Hypsizygus ulmarius

Hypsizygus ulmarius

Hypsizygus ulmarius

Hypsizygus ulmarius

Hypsizygus ulmarius

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Meyers, R. (2004, July). Hypsizygus ulmarius. Retrieved from the MushroomExpert.Com Web site: