Hohenbuehelia petaloides

🏷️ Description

🔬 Taxonomy & Naming: Originally described in 1785 by Jean Baptiste François Pierre Bulliard, this unique mushroom was later moved to the Hohenbuehelia genus in 1866 by Stephan Schulzer von Müggenburg. It has also been known as Hohenbuehelia geogenia and Pleurotus petaloides, reflecting its close resemblance to oyster mushrooms (Pleurotus spp.).

🍽️ Edibility: Although Hohenbuehelia petaloides is technically edible, its tough, rubbery texture makes it less desirable for culinary use.

Common names: Leaflike Oyster, Shoehorn Oyster Mushroom.

🔎 Identification

🍄 Cap: 1.18 to 3.54 inches (3 to 9 cm) across, often shoehorn-, fan-, or petal-shaped. Dark brown to grayish-brown, fading to tan or beige with age. Sticky to moist when fresh, with a smooth or slightly fuzzy surface.

🍃 Gills: Deeply decurrent (running down the stem). Whitish to creamy-yellow with age. Crowded and narrow, often wavy in dry weather.

📏 Stem: 0.39 to 1.97 inches (1 to 5 cm) long, 2–10 mm thick, tapering downward. Continuous with the cap, off-center or lateral. Whitish to brownish, often fuzzy near the base.

🥩 Flesh: Rubbery and pliant. White to buff-colored, sometimes gelatinized in the upper layer. Does not change color when sliced.

👃 Odor & Taste: Mealy (flour-like) odor and taste.

🧪 Chemical Reactions: KOH on cap: Negative (no color change).

🔬 Spore Print & Microscopy:

• Spore print: White.

• Spores: 5–10 × 3–5 µm, ellipsoid, smooth, hyaline in KOH, inamyloid.

• Cystidia: Pleurocystidia are lanceolate to fusoid ("metuloids"), often thick-walled.

🏞️ Habitat & Distribution: This saprobic fungus thrives on decaying wood, often appearing in urban settings, gardens, and wood chips, though it can also be found in natural woodlands. It has a cosmopolitan distribution 🌍, growing in North America, Venezuela, Europe, Japan, and New Zealand. Like many species in the Pleurotaceae family, it is nematophagous 🪱—capable of trapping and digesting nematodes!

👀 Look-Alikes

1. Pleurotus ostreatus (Oyster Mushroom): Lacks the gelatinous layer and has different microscopic features.

2. Tapinella panuoides: Found in wood chips but has yellowish-brown gills and spores.

3. Lentinellus cochleatus: Grows directly on wood, has serrated gill edges, and a more pronounced stem.

📜 Synonyms

• Omphalomyces mutilatus Battarra (1755)

• Agaricus petaloides Bulliard (1784)

• Agaricus anomalus Persoon (1796)

• Agaricus spathulatus Persoon (1801)

• Agaricus petaloides var. ß spathulatus (Persoon) Fries (1821)

• Agaricus auricula Persoon (1828)

• Agaricus putatus Persoon (1828)

• Pleuropus spathulatus (Persoon) Zawadzki (1835)

• Agaricus semitectus Berkeley & M.A. Curtis (1867) [1869]

• Pleurotus petaloides (Bulliard) Quélet (1872)

• Pleurotus petaloides subsp.* spathulatus(Persoon) P. Karsten (1879)

• Pleurotus spathulatus (Persoon) Peck (1886) [1885]

• Pleurotus petaloides var. spathulatus (Persoon) Saccardo (1887)

• Geopetalum petaloides (Bulliard) Patouillard (1887)

• Pleurotus semitectus (Berkeley & M.A. Curtis) Saccardo (1887)

• Dendrosarcus petaloides (Bulliard) Kuntze (1898)

• Dendrosarcus semitectus (Berkeley & M.A. Curtis) Kuntze (1898)

• Geopetalum semitectum (Berkeley & M.A. Curtis) Murrill (1916)

• Acanthocystis petaloides (Bulliard) Kühner (1926)

• Pleurotus petaloides var. eupetaloides Pilát (1935)

• Resupinatus petaloides (Bulliard) Kühner (1980)

• Nematoctonus geogenius Thorn & G.L. Barron (1986)

• Hohenbuehelia spathulata (Persoon) Singer (1989)

Photo sources:

Photo 1 - Author: Bruce Bailey (CC BY 4.0)

Photo 2 - Author: Michael J. Papay (CC BY 4.0)

Photo 3 - Author: Annie Weissman (Public Domain)

Photo 4 - Author: Tatiana Strus (CC BY 4.0)