Pleurotus ostreatus

Scientific name:  Pleurotus ostreatus (Jacq.) P. Kumm.
Derivation of name:  Ostre- means "oyster" and atus
means "resembling."
Synonyms:  Agaricus ostreatus Jacq.
Common name(s):  Oyster mushroom.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Pleurotaceae
Occurrence on wood substrate:  Saprobic or parasitic;
solitary to more typically in overlapping clusters on living or
dead deciduous trees, on decaying logs and stumps,
sometimes on conifers; April through November, year-round
during mild periods.  
Dimensions:  Caps 5-20 or more cm wide; stipes 0.5-4 cm
long and 0.5- 3.5 cm thick. Stipes may be absent.   
Cap:  Moist or dry; smooth; variable in color: whitish to
cream, grayish to brown, some with lilac tones; oyster shell-
shaped to fan-shaped or semicircular.
Gills: Decurrent or radiating from point of attachment;
broad; whitish, yellowish in age.
Spore print: White to pale lilac-gray.
Stipe: Sometimes absent or rudimentary. If present, lateral
to eccentric or even central if fruitbodies are on top of a log
or stump; whitish; hairy at base.
Veil: Absent.
Edibility: Edible, rated as choice.
Comments: The variable forms of the oyster mushroom are
now accounted for by recognizing a species complex
consisting of Pleurotus ostreatus, Pleurotus populinus,
and Pleurotus pulmonarius. Unlike the other two species,
P. populinus appears to be restricted to trees in the genus
Populus (aspens and cottonwoods). The three species
exhibit differences in morphology, color, host/substrate, and
fruiting season. The web sites below contain additional
information about this complex of three closely related
species which have all at one time or another been called
Pleurotus ostreatus.

More information at   
More information at

Figure 1.This Norway maple (Acer platanoides) street tree
is parasitized by an oyster mushroom species.
Photo © Gary Emberger.

Figure 2. Close-up of a cluster of oyster mushroom caps
fruiting on the tree in Figure 1. Given the distinct brownish
color and late season growth (December), this species is
most likely Pleurotus ostreatus. Photo © Gary Emberger.

Figure 3. Although these oysters appear to be growing in
grass, they are actually growing on buried wood. A large
pin oak tree (Quercus palustris) was removed from this
site just a few years before the picture was taken.
Photo © Gary Emberger.

Figure 4. The oysters of Figure 3. These were growing in
January during a period of exceptionally mild weather. Late
season oysters often are tan or gray in color. In addition,
these caps produced a distinctly gray-lilac spore print,
also charactristic of Pleurotus ostreatus.
Photo © Gary Emberger.

Figure 5. November fruiting of Pleurotus ostreatus
growing on a log in a stream. Photo © Gary Emberger.

Figure 6. In contrast to the mushrooms in Figures
1-5, these oysters were fruiting in June. The growth
in summer and lighter cap color are typical of
Pleurotus pulmonarius. Photo © Gary Emberger.

Figure 7. Another cluster of caps of Pleurotus pulmonarius
growing on a log near the tree in Figure 6 on the same day.
Photo © Gary Emberger.

Figure 8. Underside of the cluster of caps in Figure 7.
Photo © Gary Emberger.

Figure 9 Oyster mushroom typically grows in overlapping
clusters. Photo © David Work.

Figure 10. Decurrent gills. Photo © David Work.

Figure 11. Oyster mushroom on a stump. Logs are another
common habitat. Photo © William Roody.

Figure 12. Oyster mushrooms with brownish/violet coloration.
Photo © Pam Kaminski.

Figure 13. A yellowish, commercially cultivated species
(probably Pleurotus citrinopileatus) of oyster mushroom.
Photo © Gary Emberger.


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