Pleurotus pulmonarius — Oyster mushrooms

Oyster mushrooms

Oyster mushrooms1 on a mossy alder log, photograph by David Carmean.

Oyster mushrooms

Oyster mushrooms10 photograph by Yves Lamoureux.

Oyster mushrooms

Oyster mushrooms10 on dead alder (Alnus rubra) trunk, photograph by Adolf Ceska.

Odour: Pleasant
Cap: 5–25 cm in diameter, not round, but fan- or shell-shaped with a stem that is off-centre, at the side of the cap. Starting out rounded, but with age becoming flat or wavy. The colour is white to grey-brown, or purplish grey. The surface is smooth and dry.
Gills: Decurrent, descending down the stem, well-spaced to crowded, white to buff.
Stem: 0.5–3 cm long x 0.5–2 cm wide, short or almost absent, usually lateral rather than central, pale coloured. The surface is smooth, sometimes with hairs or fluff at the base.
Ring or veil: None.
Cup: None.
Spores: 10–14 x 5.5–7 µm, smooth.
Habitat: Fruiting in shelf-like, overlapping clusters or singly, on branches, trunks and logs of deciduous trees such as alder (Alnus sp.), cottonwood and aspen (Populus spp.), and willow (Salix sp.). Easily cultivated on all kinds of substrates (coffee grounds, saw dust, straw bags, wood chips etc.), and therefore commercially grown.
Geographical range: In northern and mountainous regions of North America, also Europe and Asia.

Oyster mushrooms are among the easiest edible mushrooms to identify. Similar-looking species in our region are generally not highly poisonous.

One of the few poisonous mushrooms that could conceivably be mistaken for an Oyster is the Jack-o-lantern mushroom (Omphalotus olivascens). Jack-o-lantern mushrooms resemble Oyster mushrooms in form and like them, they grow on wood. However, jack-o-lantern mushrooms are orange or olive to ochre in colour rather than white or beige; they have yet to be reported from BC, and the few records from Oregon and Washington have yet to be verified5.

Oyster mushrooms in BC and the Pacific northwest had usually been identified as Pleurotus ostreatus, a species that is difficult to distinguish from P. pulmonarius and P. populinus6. Pleurotus pulmonarius at least occasionally grows on alder (Alnus spp.); whether this is the most common species on alder in BC and the Pacific northwest remains unclear. The description above is a generic description for non-veiled oyster mushrooms. In the Rocky Mountains and possibly also in BC and the Pacific northwest, Pleurotus populinus may be the common oyster mushroom growing on wood of black cottonwood and aspen (Populus trichocarpa and P. tremuloides)6.

Other mushrooms with a lateral stem include the angel wings (Pleurocybella porrigens), which grow exclusively on wood of coniferous trees and are pure white, with flesh so thin that the cap is almost translucent. Angel wings had been considered edible but can no longer be recommended because in 2004 in Japan, 59 people were hospitalized and 19 died after eating the species7. Hohenbuehelia species have a gelatinous layer under the cap surface and may be shoehorn or funnel shaped rather than shelf-like as in oyster mushrooms. Crepidotus species are usually smaller, thin-fleshed, with brown spores.

Oyster mushrooms are generally regarded as safe to eat and they are grown and sold commercially. However, commercial harvesters of oyster mushrooms sometimes develop allergies to the spores (and hence, spore-free cultivars are now produced)8. Individual reactions to oyster mushrooms differ, and a rare few people develop symptoms such as gastrointestinal distress after eating them9.

Treatment: Contact your regional Poison Control Centre if you or someone you know becomes ill after eating oyster mushrooms. Poison Centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.

Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.

Specimen Pleurotus pulmonarius UBC F29191, GenBank #MH718206.

Siegel, N. & Schwarz, C. Mushrooms of the Redwood Coast. A Comprehensive Guide to the Fungi of Coastal Northern California. Ten Speed Press, Berkeley, California (2016).

Trudell, S. & Ammirati, J. F. Mushrooms of the Pacific Northwest. Timber Press, Portland, Oregon (2009).

Desjardin, D. E., Wood, M. G. & Stevens, F. A. California Mushrooms: The Comprehensive Identification Guide. Timber Press, Portland Oregon (2015).

MyCoPortal. Mycology Collections Portal, <> accessed February 2018.

Vilgalys, R., Smith, A., Sun, B. L. & Miller, O. K. Intersterility groups in the Pleurotus ostreatus complex from the continental United States and adjacent Canada. Canadian Journal of Botany-Revue Canadienne De Botanique 71, 113-128, doi:10.1139/b93-013 (1993).

Gonmori, K., Fujita, H., Yokoyama, K., Watanabe, K. & Suzuki, O. Mushroom toxins: a forensic toxicological review. Forensic Toxicology 29, 85-94, doi:10.1007/s11419-011-0115-4 (2011).

Baars, J. R., Sonnenberg, A. S. M., Mikosch, T. S. P. & Van Griensven, L.J.L.D. Development of a sporeless strain of oyster mushroom Pleurotus ostreatus pp. 317-323 in Science and Cultivation of Edible Fungi (ed Van Griensven, L.J.L.D.) Balkema, Rotterdam (2000).

Beug, M. W., Shaw, M. & Cochran, K. W. Thirty-plus years of mushroom poisoning: Summary of the approximately 2,000 reports in the NAMA case registry. McIlvainea 16, 47-68 (2006).

Cercle des Mycologues de Montréal Fungarium #CMMF002347. Pleurotus populinus <> accessed March 14, 2018.

Specimen Pleurotus pulmonarius UBC F28192; MO 132563, GenBank #MH718200.