Editor’s Note:

In my effort to catalog some of our more common North Carolina and eastern U.S. mushrooms, I have done little to touch on the varied species in the genus Pleurotus, which are generally called “oyster mushrooms.” Oyster mushrooms are one of the world’s most popular edible mushrooms and they are insanely easy to cultivate at home.

In the future, I will post some basic ideas on how to grow these delicious, healthy, and fast-growing mushrooms in your home or garden. For now, however, I want to take a peek at two species of Pleurotus that grow wild in North Carolina and are common edibles this time of year: Pleurotus dryinus, commonly called the veiled oyster mushroom, and Pleurotus levis, which is a closely related species that is nearly challenging to tell apart from the veiled oyster mushroom.
If you’re like me, this time of year means a lot of chanterelle, black trumpet, lobster, hedgehog, and chicken of the woods hunting, and during your travels you’re very likely to stumble across some oyster mushrooms as well. In the summer, the veiled oyster mushroom grows like gangbusters all around the NC Piedmont and Research Triangle area, so Pleurotus dryinus and Pleurotus levis are good species to add to your watch list!
Yours In Fungal Fancy,
Mushroom Anna

The Veiled Oyster Mushroom, Pleurotus dryinus

The edible veiled oyster mushroom, Pleurotus dryinus, is a common sight in the oak and beech forests of the North Carolina Piedmont. It fruits through the spring, summer, and early fall, and often grows in clusters of several individuals on downed logs, stumps, and dying trees. It is a member of the Pleurotus genus, which includes many different species of edible oyster mushrooms. The word Pleurotus means “side ear,” which is an apt description, because these mushrooms tend to grow laterally off the side of dead and decomposing wood, and many of them are somewhat ear-shaped (although kidney- or oyster-shaped more accurately describes it in most instances).
As a wood decomposing saprophyte, Pleurotus dryinus is not a terrestrial mushroom, and I find it both on recently felled wood and logs and stumps in a relatively advanced state of decomposition. It does quite well in the summer in North Carolina, although I’ve found it as early as mid-March in the North Carolina Piedmont. The veiled oyster mushroom is a relatively large species, often getting to 4-5 inches in cap diameter when fully grown.

Pleurotus dryinus is edible, although when it gets large it can become a bit on the tough side. The flavor is much like other oyster mushrooms (by which I mean mild and pleasant), although its fuzzy cap and occasionally prickly-furry stem and cap can be a little like gnawing on a woolen sock, so whenever I gather a particularly hairy specimen of the veiled oyster mushroom, I carefully skin it before slicing it up for cooking.
The veiled oyster mushroom is a bit of an enigma to mushroom fanatics because even though it’s an oyster mushroom, it doesn’t have a lot of the characteristics that make a Pleurotus mushroom…well…a Pleurotus mushroom. To start with, Pleurotus dryinus usually has a central stem that can get quite long, whereas most oyster mushrooms have an off-center stem that is short and stumpy, and some oyster mushrooms lack a stem altogether (in most instances, oyster mushrooms have a stem of some sort, but it’s often buried inside the wood from which the mushroom fruits, and so it’s not always obvious to the casual observer).
Also, Pleurotus dryinus at times does not fruit from the side of a tree or stump but sprouts right from the top of its woody food source. This is a nice feature when it occurs because I can often spot them at quite a difference as they hold their mushroomy heads high off felled trees.

Unlike other mushrooms in the oyster mushroom complex, Pleurotus dryinus has a veil of tissue that covers the gills of the developing mushroom, hence its common name “veiled oyster mushroom.” As Pleurotus dryinus matures, the partial veil bursts, usually leaving a ring of tissue on the stem. The stem-ring (or annulus, which is fancy mycology lingo for the remains of a partial veil that remains on a mushroom’s stem) of the veiled oyster mushroom is usually ragged and flaky and can be peeled off the stem with ease. At times, the ring will wear off as the mushroom ages, but another feature that can help ID Pleurotus dryinus is that the edge of the cap will sometimes have flakes of the partial veil tissue stuck to it.

Pleurotus dryinus tends to have relatively tough flesh and sticks around for a while after it fruits, and so this partial veil can and often does wear away, but it’s usually easy to tell where the ring once was, because the lower portion of the stem is often darker in color than the upper portion of the stem that was protected by the veil during the mushroom’s maturation. Furthermore, the portion of the stem that was not initially veiled is more likely to be furry or fuzzy than the portion directly below the cap.
Another distinguishing feature of the veiled oyster mushroom is its fuzzy flesh. The fuzziness of Pleurotus dryinus varies; some specimens are plushy like velveteen, and others are distinctly hairy with wiry little hairs on the cap and/or stem. While most oyster mushrooms are smooth to the touch, Pleurotus dryinus has little hairy fibers on the cap (and often the stem as well, especially at the base), and handling this mushroom is sometimes sort of like petting a geriatric mouse. The fuzziness of the veiled oyster mushroom sets it apart from lookalike species like the elm oyster mushroom (Hypsizygus ulmarius) and various other wood decomposing species. An exception is Pleurotus levis, which also has a hairy cap and stem (more on the distinction between these two species below).
Pleurotus dryinus, like all oyster mushrooms, has decurrent gills that run down the stem, and they often stop at a rather abrupt point somewhere in the upper portion of the stem. The gills are widely spaced, deep, and blade-like. The spore print of Pleurotus dryinus is white.
Pleurotus dryinus is white in color, which is yet another feature that sets it apart from other oyster mushrooms like the fawn-brown Pleurotus ostreatus. As specimens age, veiled oyster mushrooms sometimes become tinged yellow at various points on the stem, edges of the gills, and the cap. This is largely due to the fruiting body drying out, although some specimens on Mushroom Observer are remarkably yellow-colored.

Pleurotus Dryinus and Pleurotus Levis

The veiled oyster mushroom coincides with a closely related edible mushroom called Pleurotus levis. This mushroom has been called by different names over the years in different mycological sources, including Panus strigosus and Lentinus levis. 
Without getting too deep into the taxonomy of the thing, Pleurotus levis was once considered a part of the Lentinus genus (also, coincidentally, where the shiitake mushroom, Lentinula edodes, used to be placed), and then was later moved to Panus, which at that time was thought to be a subgenus of Lentinus. In the 1970s, Panus strigosus was moved to the genus Pleurotus and gained the species epithet levis, although there are plenty of people who call it a Panus to this day.

When it comes to distinguishing Pleurous dryinus and Pleurotus levis, there are a few features to be considered, but these two species can cause a little heartache to the taxonomically inclined because they are microscopically and physically so alike in appearance that one would be hard pressed to tell the difference between them in a lot of cases. However, rest assured that they are two different species and cannot mate; the difference between them is not simply due to some mushroom taxonomy splitter’s desire to drive us all mad!
One thing that might help, however, is that Pleurotus dryinus’ partial veil is more often visible. Pleurotus levis rarely has a partial veil in nature; although it forms veils in culture and there are observations of young specimens with partial veils in the wild, Pleurotus levis usually lacks it. Another distinction is that Pleurotus dryinus is thought to grow in cooler climates, whereas Pleurotus levis is noted to fruit in warm weather. Sadly for us North Carolina mushroom hunters, this is not the greatest help, because both species occur in our forests. Not to fret, however, both are listed as edible, if a little on the tough side.

Lookalikes for Pleurotus dryinus

Besides Pleurotus levis, there are a few other species to look out for that might be mistaken for Pleurotus dryinus, but on the whole I think that this species of oyster mushroom has plenty of distinct features that will prevent errors with identifying them.

The Elm Oyster Mushroom – Hypsizygus ulmarius

The elm oyster mushroom, Hypsizygus ulmarius, is a tasty species that grows on hardwood trees all around the eastern United States. It has also been reported to occur in California by David Arora, and the elm oyster mushroom is a popular candidate for cultivation. Some studies have indicated that it promotes plant growth and health when grown in partnership with garden veggies!
Like Pleurotus dryinus, the elm oyster mushroom has a central stem that, when it sprouts off the side of a tree, often becomes curved so that the mushroom cap is flat on top. Hypsizygus ulmarius is a nice edible from my perspective, but it’s best when young, because much like Pleurotus dryinus, it becomes tough with age.
Although it shares features with Pleurotus dryinus (basically being an oyster mushroom with a stem and creamy-white gills), Hypsizygus ulmarius does not have a ring on the stem and its gills are not decurrent (i.e. they do not run down the stem, but are instead attached at the top of the stem). Furthermore, it is a smooth mushroom and does not have any hairy, felty material on the cap or stem. Also, it the caps of the elm oyster mushroom tend to crack when it ages and dries, often forming beautiful geometric patterns on the surface of the cap in age.

The Bear and Fox Lentinellus, Lentinellus ursinus and Lentinellus vulpinus

These two mushrooms grow on decaying wood and look a good bit like oyster mushrooms, although their flesh is thinner and their caps are slightly hairy, and they are brown, which stands in pretty extreme contrast to the white or creamy coloration of Pleurotus dryinus. Although I think it unlikely someone would mistake these two Lentinellus mushrooms for the veiled oyster mushroom, given that they neither have stems nor veils, but the hairiness of their caps might be a confounding factor.

OK, I take it back, evidently these Lentinellus mushrooms occasionally have a rudimentary stem (in the 1-2 cm range, lengthwise), but they are often not present or are overlooked altogether. These mushrooms are considered inedible.

Panus rudis (Lentinus strigosus) and Panus conchatus

Panus rudis is a densely wooly wood decomposing mushroom that looks a good bit like Pleurotus dryinus, and it has lots of little hairs on its cap. Some sources consider Panus rudis to be synonymous with Lentinus strigosus, but it’s not entirely clear (to me at least!) that this is the case. If this mushroom genetics mystery has been positively resolved, I was unable to find verification in the sources I typically use for this blog. Panus rudis has decurrent gills, a stem that is often off-center and it has crowded gills.
Panus rudis can most easily be distinguished from Pleurotus dryinus because it lacks a partial veil, and thus mature specimens do not have a ring on the stem. When it is young, Panus rudis often is purple or lilac in color, but as it ages it can turn pinkish, tan, or reddish-brown. Its hairs are white, straight, and short, sort of like the little bristles on a caterpillar. Both the densely packed gills and the off-center stem should help in ruling out Pleurotus dryinus when you find it, because the veiled oyster mushroom tends to have a central stem and more widely spaced gills, and Pleurotus dryinus also grows larger.
Panus conchatus is another “pleurotoid” mushroom with a stem that grows from wood, but it’s quite easy to keep straight from Pleurotus dryinus. First of all, Panus conchatus has a smooth surface and lacks plushiness or hairs, and secondly it has no partial veil or ring on the stem. Finally, this mushroom tends to be purple or purple-brown in color, which makes it quite the slam dunk as far as being sure it’s not Pleurotus dryinus.

Concluding Thoughts on Pleurotus dryinus

The veiled oyster mushroom is one of the more common species in the woods of North Carolina in the summertime, although sadly many times the fruiting body is too tough and fuzzy for consumption. I prefer to eat this mushroom when it is young, because it has a pleasant chewy texture and is less likely to have furry or felty bits that stick in my teeth and make me feel like I’m noshing on my laundry. In general, I believe that this is an easy species to identify because its lookalikes are either other Pleurotus mushrooms (which are edible and choice) or lack the essential features that make Pleurotus dryinus a recognizable species (furry and veiled, with a central stem, and decurrent creamy-colored gills that are relatively widely spaced).
I suppose the only thing I would say, however, is that sometimes the veil remnant and ring on the stalk of Pleurotus dryinus is difficult to detect. Unlike other mushrooms with a ring, such as those mushrooms with partial veils in the Amanita genus, Pleurotus dryinus’s annulus can be slight and faint, especially when the mushrooms have reached full maturity. The best way to tell is from baby specimens that still have some of the partial veil attached to or covering the gills, but if you look closely, most of these mushrooms (of whatever age) have a distinctive (if small) ring of tissue on the stem.
Although Pleurotus dryinus is not my favorite oyster mushroom (that honor has to go to the king oyster mushroom, Pleurotus eryngii), it’s still an abundant and eminently edible mushroom that grows with great alacrity and abundance in the woods of North Carolina. That in and of itself makes it, in my opinion, a worthwhile species to become familiar with, even if you have no plans to eat it!