Identifying Agaricus in
By Ellen Jacobson, CMS Sociologist
It's time to unravel the mysteries of the
great Genus Agaricus, a group of mushrooms that
we all recognize, but frequently shy away from.
The characteristics of the genus include free
gills, chocolate brown spores, the presence of a
veil (ring), medium to large size and a central
stalk that separates easily from the cap. So far
so good, but how do we tell the individual
For species identification, we need to rely on
our sensitive noses and our discriminating color
perception. Agaricus fortunately have quite
distinctive odors. They may smell of almonds or
anise, have a fungal odor or emit a very
unpleasant chemical smell. It is important to
aggressively stick your nose into the gills or
the crushed flesh of a freshly squeezed mushroom
to pick up the various odors.
The staining reaction that may occur when the
stalk and/or cap is crushed can also be quite
distinctive. There may be no color change at all,
or the flesh may change to yellow, amber, red or
reddish-brown in the stalk, the cap or both. It
is best to check for odor and color changes when
the mushroom is fresh as both the smell and the
color can fade with time. Agaricus have prominent
veils that are single, double, evanescent,
pendant or sock-like. This genus is known to
cause some allergic reactions in some people. If
you have problems with store-bought Agaricus,
then be very cautious when eating wild Agaricus.
These are my rules for eating known and unknown
Agaricus. There seem to be several in Colorado
that are edible, but not well described. So,
identification to species is not always possible:
1. Do not eat Agaricus that
smells like a chemical--i.e. phenol, library
paste, etc. If you are suspicious, but can detect
no odor, begin to cook the sliced mushroom and
then smell the vapors coming from the pan.
2. Do not eat Agaricus that
stain yellow or amber at the base of the stalk
when it is cut vertically.
3. Do not confuse the
chocolate-spored Agaricus with the green-spored
Chlorophyllum, the white-spored Lepiotas and
Amanitas, or the Stropharia with attached gills.
Agaricus are very common in the city,
especially on lawns and in cemeteries and parks
where the grass is well watered. The most common
Agaricus include the following, and June seems to
be their favorite month:
1. Agaricus campestris: Found in
grass. A short-stalked mushroom with an
evanescent veil and bright pink gills when young.
The odor is fungal. Does not stain. Kid-glove
cap. Edible and delicious.
2. Agaricus bitorquis: Found in
the hard-packed, bare dirt of bus stops and
paths. Makes mushrumps (humps in the ground
caused by mushrooms beneath). Very sturdy
mushroom with a sock-like veil. Fungal odor may
show reddish brown discoloration. Edible and the
bugs like it, too.
3. Agaricus arvensis: Grows in
grass and is a tall, stately, very large mushroom
with a prominent double, cogwheel veil. It has a
distinct, sweet odor and stains yellow. It is
exceptionally delicious and is my favorite.
4. Agaricus xanthodermis: Grows
in grass and, when young, has a cap the shape of
a marshmallow--flat on top, round on the sides.
The top center of the cap usually has a greyish
brown center. The odor is UNPLEASANT, and the
base of the stalk stains instantly yellow when
cut. This is a poisonous mushroom. The medicinal
smell will become more pronounced if the mushroom
is cooked. It also tastes bad.
5. Agaricus "Ketring Park:"
A large, fleshy, heavy, underground mushroom
probably related to A. bitorquis that grows on
the edges of dead grass patches in Ketring Park
in Littleton. It is edible but has a very strong
flavor. No odor but discolors reddish brown.
6. Agaricus "Downing Street:"
A large, purple-brown, fibrillose fungi found
several times on Downing south of I-25. It grows
in the strip between the street and the sidewalk,
smells bad, and stains dark red. Most likely
related to A. Hondensis and should be considered
7. Agaricus "Gary Pickett:"
A large, delicious mushroom that grows in Alamo
Park in the mulch. Has no odor and does not
stain. Gary Picket swears that he dropped his
domestic mushroom trimmings in the park and that
these beauties were the result.
As the season marches into August and
September, the late summer high country
thunderstorms work their magic and the Mountain
Agaricus begin to appear. They share the same
genus characteristics of their city
relatives--free gills, chocolate spores, veils
and similar staining reactions and odors. Few
city mushrooms are found in the mountains; few
mountain mushrooms are found in the city with the
exception of A. campestris and
possibly A. praeclarosquamous.
In the mountains at approximately the elevation
of Evergreen and above, Agaricus grow in habitats
that have much in common with their city
counterparts. They like open, grassy fields,
conifer duff and squirrel middens, edges, and
interfaces between forest and fields. They don't
usually grow in rocky areas, near streams or on
the bare dirt of trails. Remember, they are
saprophytic, not mychorrizal, and need organic
matter on which to grow. They are usually
solitary, but may sometimes grow in groups of two
The most common Agaricus in dark conifer areas
is A. Albolutescens, a fungi
that stains obviously amber especially on the cap
and smells very strongly of almonds. Edible and a
favorite of many, A. sylvicola, another yellow
stainer whose counterpart in the city is A.
arvensis, grows in mixed aspen/conifer and is
usually solitary. It has an anise or licorice
odor and is edible.
A. Augustus is a supremely
delicious but unfortunately rare mushroom often
grows near paths or in disturbed soil and seems
to enjoy the sun. The cap and the stalk below the
veil are covered with golden brown scales or
fibrils. It has a sweet almond smell and stains
A. osecanus is a robust fungus
of fields and foothills, shines like a headlight,
and is therefore visible at great distances. It
can look like a puffball. The stalk is shaggy
below the veil; it stains yellow, and smells like
almond. This is one very delicious mushroom if
you can find it. There is one bad guy that
appears infrequently in the mountains between
7,000 and 9,000 feet usually along roads or in
disturbed earth and in great quantities.
The mushroom, A. praeclarosquamous,
has dark grey fibrils on the cap stains yellow at
the base, smells awful, and looks mean. This
could be the A. 'Downing Street' described in
We occasionally stumble on Agaricus that stain
red and have an almond odor. Once more, we can
follow our simple rule: we may eat with caution
any Agaricus that does not smell of chemicals.
The red stainers growing in Colorado include A
fuscofibrillosus, A. pattersonae, and A.
sylvaticus. All are edible.
Agaricus do not favor lodgepole, but any area
with lots of blue spruce, engelmann spruce or fir
is a good place to look for them; they are big,
bold mushrooms and very easy to find. I like to
look in the deep, dark of the woods of the
Chicago Forks area, Guanella Pass Campground and
the campgrounds on the east side of Berthoud
Pass. They can also grow at high altitude, and I
have found some intriguing, though unnamed,
collections in Church Park and the Montezuma
area. Most Agaricus are exceptionally good to eat
and may be cooked using any recipe for
supermarket or domestic mushrooms. I prefer to
discard the stems because they are tough and have
a peculiar flavor. I have also not found a good
way to preserve Agaricus; they do not dry
particularly well and tend to get flabby when
they are frozen. Pickled buttons are good, but my
favorite concoctions include A. arvensis
pizza with Fontina cheese and sage and marinated,
grilled caps of any large, edible Agaricus
species. Try these big beauties and I know you
will like them.
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