Elm Oyster
Hypsizygus ulmarius
Hypsizygus ulmarius, also known as the elm oyster mushroom, and less commonly as the elm leech. It has often been confused with oyster mushrooms in the Pleurotus genus but can be differentiated easily as the gills are either not decurrent or not deeply decurrent.
Photo: Wikimedia Commons (CC) via https://en.wikipedia.org/wiki/Hypsizygus_ulmarius
Taxonomy & Classification
Kingdom
Fungi
Phylum
Basidiomycota
Class
Agaricomycetes
Order
Agaricales
Family
Lyophyllaceae
Genus
Hypsizygus
Elm Oyster belongs to the family Lyophyllaceae, order Agaricales, within the Agaricomycetes class.
Species Profile
Hypsizygus ulmarius, also known as the elm oyster mushroom, and less commonly as the elm leech. It has often been confused with oyster mushrooms in the Pleurotus genus but can be differentiated easily as the gills are either not decurrent or not deeply decurrent.
The Elm Oyster mushroom (Hypsizygus ulmarius) faces severe decline primarily due to the widespread loss of its host trees, particularly elm species, which have been devastated by Dutch elm disease across much of its range. Habitat fragmentation and the removal of dead and dying trees for disease management have further reduced available substrate for this saprobic fungus. Climate change may also be altering the environmental conditions necessary for successful fruiting and spore dispersal.
Key Facts
Habitat & Distribution
H. ulmarius cultured on hay-infused agar (left) and potato dextrose agar (right) after five days of growth at room temperature The H. ulmarius mushroom commonly grows on tree species like elm, box elder (Acer negundo), and beech, though it may be found on other trees as well. The fungus accomplishes this by using a complex suite of enzymes that dissolve both cellulose and lignin like laccase. It...
Threats
IUCN Red List: Critically Endangered
The Elm Oyster mushroom (Hypsizygus ulmarius) faces severe decline primarily due to the widespread loss of its host trees, particularly elm species, which have been devastated by Dutch elm disease across much of its range. Habitat fragmentation and the removal of dead and dying trees for disease management have further reduced available substrate for this saprobic fungus. Climate change may also be altering the environmental conditions necessary for successful fruiting and spore dispersal.
Dutch elm disease eliminating host trees
Removal of dead elm trees for disease management
Climate change affecting fruiting conditions
Habitat fragmentation and urbanization
Loss of old-growth and mature forest ecosystems
Community Sightings
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Sources & Attribution
How to Cite
IUCN: IUCN (2025). The IUCN Red List of Threatened Species. Version 2025-1. Available at: https://www.iucnredlist.org. doi:10.2305/IUCN.UK.2025-1.RLTS
GBIF: GBIF.org (2025). GBIF Home Page. Available at: https://www.gbif.org
This page: SpeciesRadar (2025). Elm Oyster (Hypsizygus ulmarius). SpeciesRadar: Intelligence for Earth's Biodiversity. Available at: https://speciesradar.org/species/elm-oyster