Also the Summer Oyster Mushroom – Pleurotus pulmonarius
- Edibility – 3/5 – A good, meaty mushroom, great in stir-frys and to supplement other fungi.
- Identification – 2/5 – 5-20cm diameter pale to dark grey, brown or occasionally olivaceous brackets growing in overlapping tiers; crowded cream to fawn gills running down the full length of the underside, converging to a “nub” but no obvious stipe. Oyster mushrooms can be very variable in appearance according to the substrate on which they are growing. The Summer Oyster Mushroom (Pleurotus pulmonarius), which is equally edible, is considered a distinct species, identifiable by its paler cap, generally smaller size, more obvious stem and appearance in summer/early autumn. Read more about it here.
- Distribution – 3/5 – In no way rare, but I can go for long periods without encountering a good specimen
- Season – Pleurotus ostreatus: November-March – one of the few fungus that can be found during winter, fruiting is stimulated by frost. Pleurotus pulmonarius (summer oyster): May – October
- Habitat – Grows on standing and fallen trees and large branches, especially but by no means exclusively, on beech. It seems to do particularly well on lightening damaged trees.
- Ecological Role – Oyster Mushrooms are sometimes weakly parasitic but more often saprobic. The mycelia of oyster mushrooms captures nitrogen by actively hunting for nematodes (microspcopic worm-like organisms) within its substrate. It lassoes them, paralyses them, then probes into the still-living creature’s mouth before releaseing proteins that digest it from the inside out. Pretty exciting stuff. Mature oyster mushrooms are often home, food and nursery to a range of invertebrates.
- Considerate Harvesting – Leave plenty of brackets for others to admire and forage, and to mature and spread their spores. Cut from the substrate and carry your harvest gills-down in an open weave basket. The fungi might be grateful for this chance to reach new food sources: never discount the possibility that deliciousness could be an evolutionary strategy to use humans as spore-dispersers!
- Lookalikes: The olive oysterling (panelus serotinus) usually has a short, distinct stipe, yellower gills, an olivaceous cap and is usually smaller, flimsier and slimier than true oyster mushrooms. It is considered edible (especially in Japan where it is known as Mukitake and cultivated for its flavour and medicinal properties in the treatment of liver disease) but some research suggests that it may increase the risk of certain cancers – see below for picture and more information. Angel wings (Pleurocybella porrigens) are pale and flimsier, growing only on rotting conifers and come with some very serious considerations – see below.
Oyster mushrooms are becoming quite familiar to most people as they are easy to cultivate and commonly sold in delicatessens and large supermarkets. Rather annoyingly, farmed oyster mushrooms tend to be misleadingly marketed as “wild” mushrooms – read more on this here. There are several subspecies of oyster mushroom, some of which can grow enormous – like the 4kg beauty shown below. Probably the most beautiful mushroom I have ever seen.
They are tasty, meaty mushrooms when in good condition – great for everything from soups to stews, stir-fries to barbecues. They also dry well. Older specimens make excellent mushrumami – a delicious savoury seasoning. See how to make it here.
If you think you have come across some particularly pale, ghostly and flimsy oyster mushrooms growing from mossy conifer stumps and fallen wood in dank coniferous woodland, then you are more likely to have found angel wings (Pleurocybella porrigens). True oyster mushrooms do not grow on conifers, so you are unlikely to confuse them: angel wings are always ghostly white throughout and have a feeling of cold chamois leather. Angel wings used to be considered quite rare, but now seem quite common in older conifer plantations, particularly in Argyll and the West Highlands in the autumn (but seldom in the winter, when true oyster mushrooms tend to fruit). More recently I have found them in Northern England, and heard isolated reports of them in southern English conifer plantations. It is a very beautiful fungi to find in dank misty woodland.
Despite its long history of having been eaten (especially in Japan, though I know some people in the UK who eat them regularly with no ill-effects), there is now clear evidence linking compounds in angel wings with potentially catastrophic brain damage:
“It contains a precursor to an amino acid that does not occur naturally in human bodies. When people with poor kidney function consume this precursor, and it reaches the brain, the amino acid will form, and this can cause severe brain damage, leading to death.”
Or there is a much more accessible digest/discussion of the science and safety here.
There should be some questions about the usefulness of force-feeding rats 100’s of times their own body weight of anything, then drawing parallels with sporadic and limited human consumption. This opens up a whole world of discussion on “edibility”. It isn’t as black and white as people like to think. There are many variables, including dosage, bioaccumulation in the fungi and in the consumer, variations in phenotypes, our own biochemical predisposition (presumably those that eat large amounts of angel wings with impunity are lucky enough to have good kidney function), as well as the age and condition of the plant or mushroom in question. You can read more about this in this blog:
A less worrying misidentification often occurs with the olive oysterling (panelus serotinus), which is widely used as food and medicine in Japan, but can have a tendency to taste bitter when growing on certain substrates, and has been linked with an increased risk of some cancers. Research on this appears to be in German by mycologist Andreas Gminder. If anyone has access to an English version of the research, I’d love to see it and share it here.