Leucoagaricus americanus

Scientific name:  Leucoagaricus americanus (Peck)
Vellinga
Derivation of name: Americanus means "American" or
perhaps "New World."
Synonyms:  Agaricus americanus Peck; Lepiota
americana (Peck) Sacc.; Leucocoprinus americanus
(Peck) Redhead
Common name(s):  Reddening Lepiota
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Agaricaceae
Occurrence on wood substrate:  Saprobic; several or
gregarious on stumps, sawdust, tree removal sites, wood
chips and lawns and meadows; July to October.
Dimensions:  Caps 3-15 cm wide and stipes 7-14
cm long and 0.5-2.5 cm thick.  
Cap: Dry; smooth at first but becoming scaly with reddish
to reddish-brown scales, center remaining smooth; whitish
between scales but reddening with age and/or drying,
staining reddish with handling.      
Gills: Free; white, bruising yellow-orange, reddish to
reddish-brown with age.
Spore print:White.
Stipe: White, becoming reddish to reddish brown with age,
bruising yellow-orange when young, then slowly reddish;
bowling pin or spindle-shaped.
Veil: Present, sometimes movable, sometimes evanescent.
Edibility: Although edible, it is not recommended for
novices due to similarities to poisonous Amanita species
and Chlorophyllum molybdites.
Comments: A combination of distinctive traits
characterize this mushroom: the unusual stalk shape, the
yellow to orange staining of fresh specimens, and its
tendency to age or dry overall reddish.

More information at MushroomExpert.com:

Figure 1. Leucoagaricus americanus growing at the site
where a tree was removed. Photo © Gary Emberger.

Figure 2. These specimens of Leucoagaricus americanus
are growing on a stump, another typical habitat.
Photo © Gary Emberger.

Figure 3. A closer view of the specimens in Figure 2.
Photo © Gary Emberger.

Figure 4. The ring can fall off which can lead to confusion
when trying to identify this mushroom. Photo © Gary
Emberger.

Figure 5. This specimen shows the ring and the spindle-
shaped (or the shape of a stretched out bowling pin) stalk.
Photo © Gary Emberger.

Figure 6. The cap is scaly but the center usually remains
smooth. Photo © Gary Emberger.

Figure 7. When young, all parts of the mushroom bruise
yellow to orange to reddish. Photo © Gary Emberger.