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 MushroomExpert.com:   
More information at TomVolkFungi.net:


Figure 1. Oyster mushrooms typically grow in overlapping
clusters. Photo © David Work.


Figure 2. If a stipe is present, the gills will be decurrent.
Photo © David Work.


Figure 3. An oyster mushroom species is parasitizing this
Norway maple (Acer platanoides) street tree.
Photo © Gary Emberger.


Figure 4. 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 5. 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 6. The oysters of Figure 3 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 that
is charactristic of Pleurotus ostreatus.
Photo © Gary Emberger.


Figure 7. November fruiting of Pleurotus ostreatus
growing on a log in a stream. Photo © Gary Emberger.


Figure 8. Pleurotus ostreatus. Photo © Pam Kaminski.


Figure 9. In contrast to the mushrooms in Figures
3-8, these oysters were fruiting in June. Fruiting in
summer and a lighter cap color are typical of
Pleurotus pulmonarius. Photo © Gary Emberger.


Figure 10. A cluster of Pleurotus pulmonarius caps
growing on a log near the tree in Figure 9.
Photo © Gary Emberger.


Figure 11. Underside of the caps in Figure 10.
Photo © Gary Emberger.


Figure 12. A beautiful fruiting of Pleurotus pulmonarius in early
September. The picture was taken along the Appalachian
Trail in Pennsylvania. Photo © Amber Wingert.


Figure 13. Caps, gills, and stipes of additional specimens growing
on the tree in Figure 12. Photo © Amber Wingert.


Figure 14. A yellowish, commercially cultivated species
(probably Pleurotus citrinopileatus) of oyster mushroom.
Photo © Gary Emberger.

 

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