A Skeleton Trial Key to TRICHOLOMA in the Pacific Northwest

Prepared for the Pacific Northwest Key Council
by Coleman Leuthy 1996
Copyright © Pacific Northwest Key Council 1996, 1997, 2019
Minor revision by Ian Gibson 2019
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The following species were added:
1) Tricholoma apium with an odor of celery, a whitish cap and a stem that often narrows downward,
2) Tricholoma nigrum described in 1996 from Oregon,
3) Tricholoma aurantio-olivaceum originally described from Washington, and
4) Tricholoma muricatum in the Tricholoma pessundatum group, described by K. Shanks as a new species from California and documented from Washington and Oregon by S. Trudell. Other species in the T. pessundatum group as outlined by D. Arora are T. albobrunneum, T. fulvum, T. pessundatum, T. ustale, and T. ustaloides. All of these have been reported from the Pacific Northwest and backed by herbarium vouchers at the University of Washington or University of British Columbia, but they all have an asterisk in the key indicating that confirmation is required, ideally by molecular means.

The publication of Tricholomas of North AmericaA Mushroom Field Guide by A.A. Bessette, A.R. Bessette, W.C. Roody, and S.A. Trudell in 2013 provided a much needed resource.

This field guide supported the concept of T. aurantio-olivaceum – it is not clear why it was left out of the original key. It also mentioned reports of several other Tricholoma species from the Pacific Northwest which if confirmed should be added to the key. These include T. dryophilum, said by Bessette et al. to have been reported under Garry oak in southern Washington, and T. moseri, said by Bessette et al. to have been reported from the Washington Cascade Mountains. They also said that a collection from Idaho provided a 99% DNA sequence match with a French collection of T. arvernense, and similar collections later came to light in Oregon.

The definition of Group 2 was changed to “Having a strong non-farinaceous odor”. The logic in Group 4 was improved. Tricholoma sejunctum and T. subsejunctum were combined as Tricholoma sejunctum group as it is not clear what the correct name is. The undescribed ‘tea-green’ species was eliminated as it may represent Hygrophorus caeruleus.



This key is a trial field key to species reported in the Pacific Northwest.

The species marked with an asterisk need confirmation for the Pacific Northwest and some of them will not be included in the final key.

I Annulus present:

Floccularia albolanaripes T. focale
Floccularia luteovirens T. murrillianum (T. magnivelare misapplied)
T. aurantium (T. robustum)*
T. caligatum T. vernaticum
T. cingulatum  


II Having a strong non-farinaceous odor:

T. apium T. platyphyllum
T. bufonium T. sulphurescens
T. inamoenum T. sulphureum
T. odorum  


III Color of cap:


A White to pale or pastel

T. farinaceum T. subluridum
T. silvaticum*  


BYellow, orange, reddish orange, green or with a green component

T. aestuans* T. psammopus*
T. aurantio-olivaceum T. saponaceum
T. aurantium T. sejunctum group
T. davisiae T. subluteum*
T. equestre  


C Reddish brown or brown but not gray – black in the base color, fibrils may be +/- black

T. albobrunneum* T. stans*
T. fulvum* T. striatum
T. imbricatum T. subumbrinum
T. muricatum T. ustale*
T. pessundatum* T. ustaloides*
T. populinum T. vaccinum
T. psammopus* T. venenatum


D Gray to black, especially fibrils, etc.

T. acre* T. huronense T. pardinum
T. argenteum* T. luteomaculosum T. portentosum
T. atrodiscum* T. mutabile T. scalpturatum
T. atrosquamosum* T. myomyces T. terreum*
T. atrosquamosum var. squarrulosum* T. nigrocystidium nom. prov.* T. triste*
T. atroviolaceum T. nigrum T. umbonatum*
T. cingulatum T. orirubens* T. virgatum


* These species need confirmation for the Pacific Northwest.



Group 1 – Species with an annulus – 9 species

1a Cap surface entirely some shade of yellow

1b Cap surface not entirely yellow, or some other color

2a Cap with brownish to blackish radiating fibrils, without upturned scales, surface slightly viscid only when moist.

2b Cap with light colored, upturned scales, surface moist and sticky.

3a (1b) Cap surface bright orange; stem uniformly orange below with almost concentric scale-flakes around the mid-portion, the upper part white

3b Cap surface orangish and/or of other colors

4a Cap surface orangish, reddish orange to chestnut or date brown often with green tones; stem tapering at base

4b Cap surface either gray, or white to whitish gray with flattened fibrils; fibrils grayish or cinnamon-brown to chestnut or vinaceous

5a Cap orange to orange brown, often lighter on the margin, at times showing some olive-green tints; strong farinaceous smell especially when split open; stem short and stout, tapering at the base. Armillaria zelleri = Tricholoma zelleri =

5b Cap chestnut to coppery or reddish brown; stem longer and cylindrical, tapering at base; known from Europe and Japan, not known to occur in North America

6a (4b) Cap gray, brownish or bluish

6b Cap white and or with few to nearly covered by brown fibrils so as to appear brown

7a Cap gray to bluish gray sometimes developing olivaceous tones, sometimes overlaid with white cottony or fibrillose veil remnants forming a patch in center of cap; smell distinctive of cucumber or watermelon rind.

7b Cap gray-beige to gray-brown, yellowing in age, smooth to finely and radially fibrillose; odor farinaceous - mealy

8a (6b) Cap white, sometimes streaked or with splotches of brown (? grayish to grayish brown); a robust species with cap 8 - 20 cm or larger; stem expanded at base often with brown streaked areas; odor distinctly spicy-aromatic.

8b Cap base color white, but cap appearing deep brown by flattened cinnamon-brown to chestnut or vinaceous fibrils, sometimes separating in age revealing a whitish or pinkish flesh; stem also covered with brown fibrils; smaller and more slender cap 4 - 12 cm broad; odor spicy-aromatic.


Group 2 – Species with a strong odor – 7 species

1a Cap reddish brown to purple reddish brown

1b Cap white to yellow

2b Odor of celery

2b Odor of coal tar gas – sulfur aromatic, noxious somewhat sweetish

2c Odor fruity of of jessamine or coconut

3a Cap, gills, stem, and flesh yellow

3b Cap whitish to pale yellow gray or yellow buff

4a Cap dingy white to pale yellow gray; gills white sometimes blackening; stem whitish yellow, can brown at base

4b Cap white to yellow buff; gills white to light buff, on aging dark yellow; stem whitish

5a (2c) Does not bruise yellow; odor of jessamine blossoms to nutty and farinaceous; cap grass yellow to yellow with a brown center; gills yellow fading to buff; stem yellow fading to buff, bruising brown at base

5b Gills and stem spotting yellow when touched; odor fruity or coconut, nutty and somewhat acrid; cap white with yellow to orange yellow patches; gills white to cream yellow


Group 3 – CAP white – pale, pastel (see also the strongly odorous species in Group 2)

1a Cap to 4 (5) cm

1b Cap to 7 or 8 cm

2a Cap white with a bluish tint, centered blackish, prominent umbo

2b Cap white, subumbonate

3a (1b) Cap whitish, dry, glabrous

3b Cap cream to dingy white with fine brown to gray fibrils. A white form of Tricholoma scalpturatum (see Group 6)

Note: Tricholoma argyraceum, T. inocybeoides, and T. myomyces var. alboconicum were synonymized into T. scalpturatum (Guilden 1992)


Group 4 – CAP yellow, orange, reddish orange, green or with a green component – 9 species

1a Cap somewhat greasy-looking, not viscid; greenish gray, olive, yellowish olive, grayish brown, gray; stem pinkish inside near base and often outside, odor mild to farinaceous or soapy or rancid with a sweet overtone or “of washrooms”

1b Not with these characters

2a Stem slender and silky, usually more than 8 times as long as wide; cap dry, orange to orange brown; stem with orangish to brownish fibrils or scales; odor mild

2b Not with these characters

3a Cap viscid, orange to orange-brown or red-brown, sometimes splashed with olive or entirely olive; stem with belts of rusty orange scales; odor farinaceous

3b Not with these characters

4a Cap yellow to brown or sometimes olive-yellow, viscid when wet, without conspicuous black to brown radiating fibrils; stem white to yellow

4b Not with these characters

5a Gills yellow

5b Gills white

(T. subluteum would key here but is questionable for Pacific Northwest. Gills white but may be tinged yellow at cap edge. Bald over disc, long yellowish radial fibrils near margin.)
(T. psammopus would key here but evidence for Pacific Northwest is sparse. Cap yellow-brown to yellow, with radially aligned fibrils, appressed when young but becoming scaly in age; usually under larch. Gills white then yellow, becoming rust-spotted. Stem colored as cap, finely granular scaly.)

6a (4b) Odor farinaceous

6b Odor mild

7a Cap slightly viscid, yellowish or greenish yellow background with conspicuous black to brown radiating fibrils, gills white to yellow or greenish yellow, stem white to yellow or greenish yellow, odor slightly farinaceous or mild

7b Cap dry, not having conspicuous black to brown radiating fibrils; cap with an acute umbo, yellowish green, yellowish buff, pale buff, gray-brown, or brownish gray, darker on the umbo; stem that is light greenish yellow and silky-fibrillose, stem base white or tinged vinaceous; odor farinaceous

8a (6b) Cap slightly viscid, yellowish or greenish yellow background with conspicuous black to brown radiating fibrils, gills white to yellow or greenish yellow, stem white to yellow or greenish yellow, odor slightly farinaceous or mild

8b Cap dry, light yellowish green, greenish yellow with brown disc and often elsewhere, occasionally streaked with gray fibrils; stem silky-fibrillose, very pale yellow-green, odor mild

Two varieties are noted: T. coryphaeum (Fr.) Gillet = T. sejunctum var. coryphaeum, and T. intermedium Peck = T. sejunctum var. intermedium. This is intermediate between T. sejunctum and T. flavovirens.


Group 5 – CAP reddish brown or brown – 16 species

1a Cap fibrillose to scaly to the touch, dry

1b Cap smooth to the touch (but may be innately fibrillose), moist to viscid in rainy weather

2a Cap color yellowish brown

2b Cap color reddish brown

3b Cap with fibrils arranged +/- in concentric rows of appressed scales; usually under hardwoods

3a Cap with radially aligned fibrils, appressed when young but becoming scaly in age; usually under larch

4a (2b) Young buttons with cortina; stem generally hollow; habit usually gregarious or cespitose; cap color reddish brown (rusty brown), buff ground color between scales readily apparent; cap surface broken into distinct scales

4b Young buttons lacking cortina; stem generally solid; usually solitary or scattered; cap color duller, darker brown, ground color not readily apparent

5a (1b) Gills and stem flesh yellow; stem surface fibrillose, yellow to brownish; cap margin striate when young.

5b Gills and stem flesh white to pallid, maybe spotting rusty red-brown in age

6a Always growing under trees in the genus Populus (poplars, cottonwoods, aspens, etc.)

6b Habitat with either conifers or hardwoods, but not limited to Populus species

7a Cap color dirty yellowish brown; cap shape subconic; surface smooth but innately fibrillose and virgate, viscid but soon dry

7b Cap color reddish brown; cap shape not subconic, other features various

8a Cap margin usually spotted with drops or dark spots, cap and gill edges may darken in age, gills may have reddish brown spots or stains; odor mealy; stem usually short; usually with pines or spruce, or odor mild

8b Cap lacking dark spots described above, or odor mild; other features varied

9a Odor mild; usually with deciduous trees; cap red-brown with olivaceous tinge and blackening in age; gills white, then rust-spotted, old edges blackening

9b Odor farinaceous or not; usually under conifers, especially pines

10a Stem silky-fibrillose with irregular belts of recurved fibrils, pruinose at top, stem overall becoming brown to brownish orange, darkening from base up or bruising with handling; cap streaked from innate radiating fibrils, margin often ribbed

10b Stem apex clearly delimited by a pseudoannular white zone, length average; cap margin finely streaked with darker lines.

T. ustaloides could key here too – it is said to have a transient cortina and sharply defined white apical zone.

10c Stem with longitudinal fibrils sometimes cracking to form transverse bands but lacking real annular zone; stem rather tall and slender, +/- pointed at base; cap not striate


Group 6 – CAP gray to black or the primary color of the fibrils, etc. – 20 species

1a Cap viscid

1b Cap dry

2a Cap or fibrils with gray to black or gray brown

2b Cap white to gray or cream

3a Cap fibrillose-scaly at first, dark gray overall, margin soon becoming lighter gray, moist to tacky, 3.5 - 10 cm

3b Cap with innate dark gray fibrils, sometimes tints of brown, yellow, or purple, viscid to slimy, 6 - 15 cm

3c Cap glabrous, viscid, 3 - 7 cm

4a (2b) Cap light-medium gray, may have large irregular white areas, broadly convex to +/- plane, often with a low umbo, disc dark brownish gray

4b Cap brown gray to olivaceous, cream brown, or white, somewhat conical prominent umbo, disc dusky brown, margin wavy

5a (1b) Mature cap of larger expanded specimens over 10 cm (10 - 20 cm) broad

5b Mature expanded caps less than 12 cm

6a Innately interwoven radiating fibrils, scattered squamules, firm and short stature; stem 2.5-6 cm long, cortina in button stage; odor mild, taste bitter to acrid

6b Fibrillose, scaly, or squamulose +/- upturned; stem mostly longer than 5 cm, no cortina; odor farinaceous, taste farinaceous or mild

7a Cap, gills, or stem with violet or pinkish coloration or droplets

7b Mushroom without pinkish or violet coloration

8a Cap black violet gray, 6-13 cm; gills gray pinkish tinged; stem scattered squamules darkening to violaceous or +/- yellow, 6-15 cm long

8b Cap pale gray to darkish gray - pinkish, 6-9 (12) cm, often beaded drops of clear or pink fluid or streaked pinkish; stem silky to appressed fibrils, scales, often beaded with clear or pinkish drops of fluid, 4-8 cm long

9a (7b) Cap dark grayish brown to dull yellowish brown to nearly gray, 4-12 cm; gills light buff to light gray, in age often yellow, close; stem silky fibrils some projecting, 4-8 cm long

9b Cap with pale background, gray black to gray brown scales, 7-18 (20+) cm; gills dull white, +/- toothed; stem glabrous or smooth, base stains +/- yellow or rusty, 5-15 cm long

10a (5b) Cap, gills, or stem with pink, red, or violet tones, or bruising or becoming so in age or with clear pink - red droplets on cap edge or on stem

10b No apparent coloration of pink, red, or violet to purple

11a Gills white to gray, light gray buff, and with pinkish or reddish tones

11b Gills white, dull white to gray, and or dingy buff to cream

12a Cap with violet - violaceous tones (see 8a.)

12b Cap dark brown gray - sooty gray

13a Disc dark gray, gray-black, radially fibrillose-scaly +/- flushed pink, stem base reddish; after picking cap and gills turn reddish, bruised stem +/- turning reddish or green-blue

13b Cap dark brown gray

14a Stem drab light gray buff with a light ground color, silky fibrillose; taste bitter

14b Stem gray brown, color of cap, covered with squamulose fibrils; taste mild

15a (11b) Cap conical, acute umbonate, light lilac tones, streaked surface, long innate radiating fibrils, silver gray - gray, stem white flushed pale pink, purplish pink at base, has a cortina, odor mild/absent, taste bitter

15b Cap convex to plane, with a low umbo or depressed

16a Disc black, cap black-gray and with dark red-brown tomentose, scaly, fibrils, gills white-gray to dull cream, dotted black on edge, stem equal, pale gray, taste mild

16b Cap smoky gray or gray red brown

17a Cap light smoke-gray to moderately pinkish, fibrillose gray cuticle becoming broken, appressed gray spotlike scales around disc and over margin, white flesh showing, often beaded drops of clear pink fluid or streaked pinkish along margin, gills dull white, stem clavate, silky and often pink beaded drops above, appressed-fibrillose scales below, pale gray, odor & taste farinaceous (see 8b)

17b Cap speckled salty gray-brown on a red-brown ground color, gray sooty-scaly, gills white to gray, stem center gray over slate, above and below pale, sparse cortina, odor weak fungoid, taste mild

18a (10b) Partial veil or cortina present but often fleeting - check buttons

18b No evident cortina or veil

19a Veil normally a persistent, flaring, cotton-membranous one that in age is often appressed to the stem, reticulate fibrils on cap surface likely part of the veil, white discoloring yellow

19b Veil a cortina, not persistent

20a Cap conic, acute umbonate silver gray to gray, stem base flushed pink to purplish pink (see 15a)

20b Cap more convex to low umbonate to plane or depressed

21a Cap light medium gray, a firm good sized species (see 6a)

21b Cap darker to gray-blackish or brown

22a With moderately spaced squamules, odor and taste farinaceous, veil a cortina of thin white fibrils, occasionally evident on stem for a brief time

22b Cap densely fibrillose-squamulose to granulose, odor and taste absent or week and mild

23a Stem white to very pale gray, white to grayish surface fibrils projecting, silky; cap gray, dark drab to dark brown gray; veil a cortina, white to grayish fibrils, at times leaving a soon disappearing zone of fibrils on mid to upper stem

23b Stem gray over slate, mid to lower sooty-scaly, pale on upper and (lower) part; cap speckled salty gray-brown on red-brown (ochraceous) ground, gray sooty-scaly; veil a sparse cortina

24a (18b) Odor mild, aromatic - sweet/fruity, fungoid, or absent, taste mild or bitter

24b Odor farinaceous, taste farinaceous, test with PDAB ( - )

25a Odor sweet/fruity or mild, taste bitter and a positive test with PDAB (+) = bright pink all parts:

a Odor sweet/fruity. No chemical data, but mild odor & bitter taste here shows pattern of PDAB (+) (see 13a)

b Odor mild; cap gray silvery, generally with buff near edge, disc dense, margin with concolorous innate fibrils, streaked but not distinctly banded, stem white to sordid buff, stem silky-fibrillose with surface fibrils projecting, often pruinose at apex

c Odor mild (see 6a)

d Odor mild (see 14a)

e Odor mild (see 20a)

25b Odor mild, aromatic, or absent, taste mild, test with PDAB ( - )

26a Odor mealy, aromatic peppery or of basil, slight or + farinaceous, fruity peppery, taste mild, slightly farinaceous-bitterish (see 16a)

26b Odor mild or weak fungoid, taste mild

27a Cap dark gray drab to blackish or dark brown gray, appresed fibrils + recurved or squamulose (see 23a)

27b Cap speckled salty gray brown on red brown ground with gray sooty scales (see 23b)

28 (24b) Cap convex to conical umbonate, disc almost black, margin almost slate black, dark to light gray - silvery or gray brown, finely tomentose, appressed innate radial fibrils to floccose then scaly, incurved and +/- crenate; stem white to gray white, smooth, apex floccose fibrillose, solid or persistently fibrous-stuffed, readily splitting lengthwise; cap and stem fragile

Note that there are seven other species that may key out here:
T. atrosquamosum var. squarrulosum, see 14b.
T. atroviolaceum, see 8a.
T. cingulatum, see 19a.
T. huronense, see 8b.
T. luteomaculosum, see 9a.
T. nigrum, see 3a.
T. pardinum, see 9b.
T. scalpturatum, see 22a.



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