Oyster Mushrooms

(Pleurotus ostreatus)

Description

Pleurotus ostreatus, also known as the late-fall oyster, the common oyster, or the true oyster mushroom, is a fairly common mushroom in the wild and one that is highly cultivated and the subject of much research for medical and mycoremediation purposes. While the common oyster is a relatively easy mushroom to identify with few, if any, toxic look-alikes, if you are just starting to learn about mushrooms and are attempting to consume wild foraged mushrooms, please consult a field guide or an expert to get a positive ID prior to consuming any mushroom you pick. That being said, here are the freatures you should look for to identify the common oyster mushroom:

Season: late fall through early spring, usually in the few days after a relatively warm rain

Substrate: Oyster mushrooms grow on decaying wood. While some oysters (like the pheonix oyster, Pleurotus pulmonarius) grow on conifers, P. ostreatus only grows on hardwood logs and standing trees. We have had exceptional luck finding oysters growing on tulip poplar, though we have also found some on oaks and other hardwoods.

Size: cap ranges from 5-25 cm across, stipe (if present) usually no more than 3 cm long

Cap: the cap is brown to gray to pale tan depending on specimen and moisture content; cap mostly flat but curving down slightly towards the margin; flesh moderately tender and easy to break

Gills: all oyster mushrooms have gills on the underside of the cap that are usually broadly spaced and run down the stipe (if present); gills are white to off-white

Stipe: the stipe, also known as the stem, is small and off-center, if present at all. Many oyster mushrooms attach directly to the wood from the cap, but some form a small stipe at the back of the cap to connect to the wood

Spore Print: The spore print of the oyster mushrooms is white to pale lilac

Adam Haritan has a great video on foraging oyster mushrooms that includes information on a potentially toxic look-alike, so be sure to check that out as well.

The white to pale-lilac spore print of P. ostreatus taken on aluminum foil

A large oyster mushroom found fruiting at the base of a fallen poplar tree in late December. This one was found a little to late to be good for eating (unless you’re a slug!)

Underside of above mushroom showing gills    

Cultivation Tips

Oyster mushrooms are highly cultivated because of their robust nature and ease of cultivation. The two most common methods are on logs and sawdust.

For log cultivation, dowels that have been colonized by the mycelium (called “plug spawn”) are drilled and pounded into a fresh log. The mycelium in the dowels then spreads to the log and produces mushrooms out of it.

For sawdust cultivation, bags or buckets are usually filled with a mixture of sawdust that has been inoculated with the mycelium (“sawdust spawn”), fresh sawdust, and other agricultural waste like coffee grounds. Once the entire substrate has been colonized by the mycelium it will produce mushrooms.

Both plug and sawdust spawn can be purchased at a multitude of places or made at home with the right equipment, but we have had good experience with Silver Tree Forest, a permaculture nursery in Owasco, NY.

If this sounds like a lot of work for you, you can opt for a more passive, less intensive cultivation method. Simply placing old or discarded parts of oyster mushrooms on piles of wood might be enough to get them to take hold, albeit not at the density of intensive spawn cultivation. If space is limited, intensive cultivation might be better, but in a larger forest setting, it might not be worth the effort, as oysters will happily seed themselves all over in a way that preserves genetic diversity within the species and among species.

Uses

Oyster mushrooms have a pretty impressive resume when it comes to uses.

They are a choice edible mushroom with a delicious, almost meaty flavor that adds a new dimension to any dish. They can be fried up as bacon, sautéed in omelets or stir-fries, steeped in soups and stews, added to mac-and-cheese, you name it! They are also extremely healthy, containing over 30% protein and 20% fiber by dry weight, as well as lots of beneficial vitamins and minerals [98].

Oyster mushrooms also have many medicinal agents that impart all kinds of health benefits, including anti-inflammatory, anti-viral, and anti-tumor activities [55, 99-103].

Research has also demonstrated the oyster mushrooms are excellent mycoremediators, able to decompose petroleum products, toxic pesticides, and other pollutants. This allows the fungus to be used to clean up the sites of oil spills and agricultural dead-zones and turn them back into productive habitats and ecosystems [55, 104-106].

In addition to all these, white rot fungi like P. ostreatus are important nutrient recyclers in the forest. The help to break down the lignin in dead wood, allowing the minerals and organic matter to return to the soil to be used again to create new life.

Friends

P. Ostreatus grows on dead hardwood logs. In our experience, they are especially fond of the Tulip Poplar tree.

A flush of brown oyster mushrooms growing in a log pile at the SSPP in late November

A wide-shot of above

The underside gill surface of the above oyster mushrooms

A slug found hiding behind the above mushrooms that is responsible for the bites and holes.

A flush of oyster mushrooms on the base and high up in a dead tulip poplar tree in late December.