Oysters

"If one mushroom can steer the world on the path to greater sustainability, fighting hunger, increasing nutrient return pathways in ecosystems, destroying toxic wastes, forestalling disease, and helping communities . . . rebalance waste streams that currently overload our ecosystems, oysters stand out" (Paul Stamets, Mycelium Running).

Oyster mushrooms (Pleurotus ostreatus) are heralded for both their tastiness and for their ability to remediate degraded landscapes. They grow on dead hardwood trees (rarely on live trees or on conifers) such as poplars, alders, or willows; are white, grey, tan, or brown; and grow to 25 cm broad. There is often no stalk, but if present it will be short, thick, and off-centre. The gills are white (sometimes grayish with age), fairly deep, and run down the stalk, should one be present to run down. Their name relates to the shape of the cap, which has an oysterish resemblance to it, and some claim the flavour is reminiscent of this seafood as well.

Spore-colour is a characteristic feature of mushrooms which, unlike so many other characteristics, remains constant over time and space. Spores (which are like seeds) can be observed by laying the mushroom cap, gills-down, on a piece of paper (half dark-half white paper is good to ensure a contrasting spore colour), and leaving it covered for a few hours to allow the spores to fall out, leaving a lovely "spore print". Those of oyster mushrooms are white, a characteristic which recently saved me from feasting on a similar looking brown-spored mushroom growing nearby, likely a Crepidotus.

Oyster mushrooms are well known for their ability to break-down contaminants including petroleum, mill wastewater , PCBs (polychlorinated biphenyls), PAHs (polycyclic aromatic hydrocarbons), industrial dyes, and certain pesticides; they are used as "mycoremediators" to clean up areas polluted with these toxins. They also contain medicinal properties which show promise for reducing blood cholesterol, tumour inhibition, and improving liver function in AIDS patients.

While it's hard to beat the fun of wild-foraging, oysters are also one of the easiest mushrooms in the world to cultivate. Wood, straw, coffee grounds, moist cardboard and many other substrates can be inoculated with mushroom spores or mycelium, and sometimes harvested for years. They are said to be tastiest when young, and best picked before the caps flatten. Oysters are a good source of many nutrients, notably protein, B & C vitamins, and have a mild nutty flavour. Non-humans that enjoy oysters include gnats, beetles, deer, squirrels, and even some turtles; if you'd prefer avoiding some extra protein with your oysters though, soaking them in water briefly should get rid of the little critters.

To prepare oyster mushrooms for food, it is recommended not to wash them until you are ready to cook with them, to never peel them, and to always use lemon juice or another acid in their preparation (along with butter, salt, and perhaps a little white wine). As with all wild foods there is no limit to the creative recipe ideas out there; this week's offering is for Marinated, grilled oyster mushrooms, courtesy of 'Sustainable Table'.

1 Tbsp soy sauce
1 lb fresh oyster mushrooms
1 Tbsp balsamic vinegar
1 Tbsp peanut oil
1 Tsp chopped garlic
2 Tbsp maple syrup
1 Tbsp Mongolian fire oil
1 Tbsp fresh lime juice

Mix all ingredients together and marinate mushrooms for a half-hour. Shake off excess marinade from the mushrooms and grill with coarse salt and fresh pepper for 4-5 minutes on each side on a medium-hot grill with the lid down. This technique should leave grill marks and lightly brown the mushrooms. These mushrooms may also be used as a topping for pizza, crostini, or chop up and mix with grilled onions and sour cream for a dip. Almost any marinade will be good with oyster mushrooms- you can also use beer, red wine and garlic in a pinch!

Caution: About 10% of people are allergic to oyster mushroom spores, and experience reactions such as fever, headache, congestion, coughing, or malaise. As with all mushrooms, *never** harvest, eat or serve any unless you are confident that about the species and its edibility.