For June (2009) the spotlight is on the delectable oyster
Oysters (Pleurotus ostreatus complex) are the mushroom of the month for June. The delicious oysters can be found in many environments as they are a prime wood recycler. Oysters can be found on dead and dying trees especially hardwoods like poplars (a.k.a. aspen), cottonwoods, elms, box elders, etc. though they also can occur on conifers.
The gills of the oysters are white, branched fanning out toward the cap edge and are very decurrent (running down the stalk). Oysters tend to grow in dense clusters of caps, crowded and overlapping. It is not unusual to find oyster in such quantity that a mushroom hunter ends up measuring her find in pounds. Each cap may resemble an oyster shell or fan but they grow in many shapes. The edges of the caps are often curved down and are fluted. They are smooth, and colored from off-white, to buff brown, to deep bluish grey, to gray brown. The caps range from an inch across to 6 inches though some caps as wide as 12” are not uncommon. The flesh is white, juicy and quite dense. Stalks if present are thick, become woody with age and have gills all the way to their attachment with the tree. The spore print is white with tinges of lilac.
Oysters are quite easy to cultivate and many in our club have grown oysters; particularly after a memorable Fungus Fest when one of our club members led a cultivation session with boiled straw and mushroom spawn. (See picture at right and below.)
Oysters grow throughout the year but are best in the Spring and Fall when they tend to be less buggy. Whenever there is a warm, wet thaw in the winter look for oysters in poplar groves and similar places. In the summer the oysters are often buggy with small fly larvae. To test oysters squeeze the stem area; it should be very firm. If there is some give to the stem then the oyster is buggy.
Picking oysters often involves using sticks or other implements to dislodge high growing specimens. Dr. Frances Hammerstrom in her book “The Wild Food Cookbook” Amherst Press, 1989 even describes using a small bore rifle to shoot down very high growing clusters!
This good eating mushroom is one of the first mushrooms that many new mushroom hunters learn because they are fairly easy to identify; though there are a few look-alikes.
The closest look-alike is the angels wings (Pleurocybella porrigens) which are whiter than oysters and much less dense or meaty. Angels wings have been considered edible but are more bland than the true oysters; there have been some reports of angels wings poisoning people in Japan but the reports indicate that this occurred in consumers whose health status was already compromised; people who suffer from kidney problems should approach this mushroom with caution.
The elm oyster (Hypsizygus tessulatus; a.k.a. Pleurotus ulmarius) is very close in appearance to oysters but always has a substantive, off-center stem with attached but non-decurrent gills. The elm oysters are also edible but are allegedly tough and may be best cooked slowly. They are great when added to spaghetti sauce.
There are some small, brown-spore mushrooms in the genus Crepidotus which are shell or fan shaped like oysters but they are very thin fleshed while true oysters are very meaty; the Crepidotus are not edible Finally, the late fall Panellus serotinus is a somewhat bitter mushroom with olive green to yellowish caps and ochre-yellow gills that often are slightly violet on the edges.
While oysters are often edible and delicious, as with any new mushroom, a person that has not tried oysters in the past should approach them with caution eating just a small amount the first time or two that it is tried. Any intolerance to oysters or any other new mushroom will usually be seen in those first tastings.