Elm Oyster
(Hypsizygus ulmarius)
Conservation • Description • Habitat • Ecology • Distribution • Taxonomy
Conservation Status |
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| IUCN Red List | not listed |
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| NatureServe | not listed |
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| Minnesota | not listed |
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Description
Elm oyster is a large mushroom. It is widespread but not common in eastern United States. It usually occurs singlyn or in a small cluster. It is found from August to December growing from a branch scar or other wound high in a living hardwood tree, especially elm and box elder.
The cap is 2″ to 6″ in diameter. When young, the cap is convex and the margin is rolled under. The upper surface is white and smooth. As it ages it flattens out and the center becomes slightly sunken. The upper surface turns creamy buff or tan and develops cracks, forming a pattern of small scales or patches.
The stalk is stout, 2″ to 4″ long, and ⅜″ to 1″ thick. It is whitish, solid, fibrous, smooth, dry, and usually hairless, sometimes finely hairy. It is attached centrally or slightly off center, and is sometimes enlarged at the base. There is no cup-like covering (volva) at the base of the stalk, and there are no remnants of a universal veil clinging to the stalk.
The flesh is firm and white. It is edible but tough.
The gills are closely spaced and whitish at first, becoming cream-colored with age. They are attached to the stalk but do not run down the stalk.
The spore print is white to buff.
Similar Species
Brown Beech Mushroom (Hypsizygus tessellatus) is virtually identical in size and appearance. Fresh specimens often have a pattern of round watery spots on the cap. It grows on aspens, cottonwoods, and sugar maple, and it usually occurs in dense clusters.
Habitat and Hosts
Hardwoods, especially elm and box elder
Ecology
Season
August to December
Distribution |
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Sources Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu, 10/1/2025). |
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| 10/1/2025 | ||
Occurrence |
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Taxonomy
Kingdom
Fungi (fungi)
Subkingdom
Dikarya
Phylum
Basidiomycota (club fungi)
Subphylum
Agaricomycotina (jelly fungi, yeasts, and mushrooms)
Class
Agaricomycetes (mushrooms, bracket fungi, puffballs, and allies)
Subclass
Agaricomycetidae
Order
Agaricales (common gilled mushrooms and allies)
Suborder
Tricholomatineae
Family
Lyophyllaceae
Genus
Hypsizygus
Subordinate Taxa
Synonyms
Agaricus coriipellis
Agaricus ulmarius
Agaricus ulmarius ssp. ulmarius
Agaricus ulmarius var. epiphegus
Clitocybe coriipellis
Dendrosarcus ulmarius
Gyrophila ulmaria
Lyophyllum ulmarium
Lyphyllum ulmarium
Micromphale ulmarium
Pleuropus ulmarius
Pleurotus coriipellis
Pleurotus ulmariae
Pleurotus ulmarius
Pleurotus ulmarius var. verticalis
Tricholoma ulmarium
Common Names
Elm Mushroom
Elm Oyster
Glossary
Universal veil
An egg-like structure that envelopes all or most of a developing gill mushroom. Remnants of the universal veil sometimes visible on a mature mushroom are patchy warts on the cap, a ring on the stalk, and a volva at the base of the stalk.
Volva
Also called cup. A cup-like covering at the base of a mushroom stem, sometimes buried. It is the remnants of the universal veil ruptured by the mushroom pushing through. It is found on Amanita, Volvariella, and some other mushrooms.
Visitor Photos
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Amy Stifter |
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Lynda Meyers |
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Miranda Sieh |
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I have been enjoying the photos and info on your website. I have been learning about wild mushrooms and growing cultivated mushrooms for the last few years with an experienced mentor. Today (Oct 3) I found 2 mushrooms that I think are elm oysters growing on a living box elder on my farm in East central MN. The feature that gives me pause is the texture of the stipe. It is not smooth but almost scaly or shaggy. I can not find an elm oyster look alike with a shaggy stipe. The weather has been humid, but we are in need of rain. Any advice would be appreciated. |
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Wags |
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Mark Volesky |
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Found four in western Becker County. All attached to three maple trees. |
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Kirk Nelson |
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Growing on a boxelder |
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Jessica Marquez |
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Cluster of elm oyster mushrooms growing surprisingly low (4’) off the ground on a box elder tree near Silver Creek in Quarry Hill; found Dec. 20th, 2019. (They are a frequent sight here as well as along the Douglas Trail starting in late August, but this is as late in the year as I’ve found them so intact!). |
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Jeff |
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MinnesotaSeasons.com Photos
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Slideshows
Visitor Videos
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Other Videos
Elm Mushroom (Hypsizygus ulmarius) on Tree
Carl Barrentine
Elm Mushroom (Hypsizygus ulmarius) on Boxelder
Carl Barrentine
Elm Oyster foraging - Hypsizygus ulmarius
Corie Mushrooms
Elm Oyster wild mushroom
RedFree100
Visitor Sightings
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Lynda Meyers
8/27/2022
Location: Red River at Moorhead
Apricity Apricity
Fall 2021
Location: Martin County, Fairmont, MN
Miranda Sieh
10/3/2021
Location: East central MN
I have been enjoying the photos and info on your website. I have been learning about wild mushrooms and growing cultivated mushrooms for the last few years with an experienced mentor.
Today (Oct 3) I found 2 mushrooms that I think are elm oysters growing on a living box elder on my farm in East central MN. The feature that gives me pause is the texture of the stipe. It is not smooth but almost scaly or shaggy. I can not find an elm oyster look alike with a shaggy stipe. The weather has been humid, but we are in need of rain. Any advice would be appreciated.
Wags
9/28/2021
Location: near Theodore Wirth Park in Minneapolis
Mark Volesky
9/17/2021
Location: Becker County
Found four in western Becker county. All attached to three maple trees.
Kirk Nelson
9/20/2020
Location: Fort Snelling State Park
Jessica Marquez
12/20/2019
Location: Olmsted County
Cluster of elm oyster mushrooms growing surprisingly low (4’) off the ground on a box elder tree near Silver Creek in Quarry Hill; found Dec. 20th, 2019.
(They are a frequent sight here as well as along the Douglas Trail starting in late August, but this is as late in the year as I’ve found them so intact!).
nltr
9/7/2019
Location: May Township
found growing out of crotch of young elm and out of crack in young elm. Wooded acreage
Jeff
10/14/2017
Location: Rush City
Kirk Nelson
9/10/2017
Location: Lebanon Hills Regional Park
Growing on a boxelder
MinnesotaSeasons.com Sightings |
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