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
Photo copyright held by each photographer
Do not copy photos without permission

NOTE ON REVISION

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 America – A 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.

INTRODUCTION

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:

................................................................................Group 1

II Having a strong non-farinaceous odor:

................................................................................Group 2

III Color of cap:

A White to pale or pastel

................................................................................Group 3

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

................................................................................Group 4

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

................................................................................Group 5

D Gray to black, especially fibrils, etc.

................................................................................Group 6

* These species need confirmation for the Pacific Northwest.

KEY TO TRICHOLOMA

Group 1 – Species with an annulus – 9 species

1a Cap surface entirely some shade of yellow

................................................................................2

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

................................................................................3

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

................................................................................Floccularia albolanaripes (= Armillaria albolanaripes)

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

................................................................................Floccularia luteovirens (= Armillaria luteovirens)

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

................................................................................T. aurantium

3b Cap surface orangish and/or of other colors

................................................................................4

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

................................................................................5

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

................................................................................6

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 =

................................................................................T. focale (including T. 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

................................................................................T. robustum

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

................................................................................7

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

................................................................................8

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.

................................................................................T. vernaticum (== Armillaria olida)

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

................................................................................T. cingulatum

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.

................................................................................T. murrillianum (Tricholoma magnivelare is a misapplied name)

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.

................................................................................T. caligatum (= Armillaria caligata)

Group 2 – Species with a strong odor – 7 species

1a Cap reddish brown to purple reddish brown

................................................................................T. bufonium

1b Cap white to yellow

................................................................................2

2b Odor of celery

................................................................................T. apium

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

................................................................................3

2c Odor fruity of of jessamine or coconut

................................................................................5

3a Cap, gills, stem, and flesh yellow

................................................................................T. sulphureum

3b Cap whitish to pale yellow gray or yellow buff

................................................................................4

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

................................................................................T. inamoenum

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

................................................................................T. platyphyllum

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

................................................................................T. odorum

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

................................................................................T. sulphurescens

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

1a Cap to 4 (5) cm

................................................................................2

1b Cap to 7 or 8 cm

................................................................................3

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

................................................................................T. subluridum

2b Cap white, subumbonate

................................................................................T. farinaceum

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

................................................................................T. silvaticum

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”

................................................................................T. saponaceum

1b Not with these characters

................................................................................2

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

................................................................................T. aurantio-olivaceum

2b Not with these characters

................................................................................3

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

................................................................................T. aurantium

3b Not with these characters

................................................................................4

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

................................................................................5

4b Not with these characters

................................................................................6

5a Gills yellow

................................................................................T. equestre

5b Gills white

................................................................................T. intermedium

(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

................................................................................7

6b Odor mild

................................................................................8

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

................................................................................T. sejunctum group

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

................................................................................T. davisiae

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

................................................................................T. sejunctum group

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

................................................................................T. aestuans

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

................................................................................2

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

................................................................................5

2a Cap color yellowish brown

................................................................................3

2b Cap color reddish brown

................................................................................4

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

................................................................................T. venenatum

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

................................................................................T. psammopus

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

................................................................................T. vaccinum

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

................................................................................T. imbricatum

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

................................................................................T. fulvum

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

................................................................................6

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

................................................................................T. populinum

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

................................................................................7

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

................................................................................T. subumbrinum

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

................................................................................8

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

................................................................................T. pessundatum group

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

................................................................................9

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

................................................................................T. ustale

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

................................................................................10

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

................................................................................T. muricatum

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

................................................................................T. albobrunneum (Pers. ex Fr.) Kummer (= T. striatum)

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

................................................................................T. stans

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

1a Cap viscid

................................................................................2

1b Cap dry

................................................................................5

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

................................................................................3

2b Cap white to gray or cream

................................................................................4

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

................................................................................T. nigrum

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

................................................................................T. portentosum (Fr.) Quél.

3c Cap glabrous, viscid, 3 - 7 cm

................................................................................T. nigrocystidium Ovrebo nom. prov.

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

................................................................................T. mutabile Shanks

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

................................................................................T. umbonatum

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

................................................................................6

5b Mature expanded caps less than 12 cm

................................................................................10

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

................................................................................T. acre Peck

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

................................................................................7

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

................................................................................8

7b Mushroom without pinkish or violet coloration

................................................................................9

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

................................................................................T. atroviolaceum Smith

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

................................................................................T. huronense Smith

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

................................................................................T. luteomaculosum Smith

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

................................................................................T. pardinum (Pers.) Quél.

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

................................................................................11

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

................................................................................18

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

................................................................................12

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

................................................................................15

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

................................................................................T. atroviolaceum

12b Cap dark brown gray - sooty gray

................................................................................13

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

................................................................................T. orirubens Quél.

13b Cap dark brown gray

................................................................................14

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

................................................................................T. atrodiscum Ovrebo

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

................................................................................T. atrosquamosum var. squarrulosum Konrad & Maublanc

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

................................................................................T. virgatum (Fr. ex Fr.) Kummer

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

................................................................................16

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

................................................................................T. atrosquamosum (Chev.) Sacc.

16b Cap smoky gray or gray red brown

................................................................................17

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)

................................................................................T. huronense Smith

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

................................................................................T. triste (Scop. ex Fr.) Quél.

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

................................................................................19

18b No evident cortina or veil

................................................................................24

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

................................................................................T. cingulatum (Fr.) Jacobashch

19b Veil a cortina, not persistent

................................................................................20

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

................................................................................T. virgatum

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

................................................................................21

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

................................................................................T. acre

21b Cap darker to gray-blackish or brown

................................................................................22

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

................................................................................T. scalpturatum (Fr.) Quél.

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

................................................................................23

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

................................................................................T. myomyces (Pers. : Fr.) Lange

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

................................................................................T. triste (Scop. ex Fr.) Quél.

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

................................................................................25

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

................................................................................28

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)

................................................................................T. orirubens

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

................................................................................T. argenteum Ovrebo

c Odor mild (see 6a)

................................................................................T. acre

d Odor mild (see 14a)

................................................................................T. atrodiscum

e Odor mild (see 20a)

................................................................................T. virgatum

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

................................................................................26

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

................................................................................T. atrosquamosum

26b Odor mild or weak fungoid, taste mild

................................................................................27

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

................................................................................T. myomyces

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

................................................................................T. triste

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

................................................................................T. terreum (Schaeff.: Fr.) Kumm.

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.

Tricholoma apium Paul Kroeger	Tricholoma argenteum Michael Beug	Tricholoma atrosquamosum Ben Woo	Tricholoma atroviolaceum Andrew Parker
Tricholoma aurantium Michael Beug	Tricholoma bufonium Andrew Parker	Tricholoma caligatum Michael Beug	Tricholoma cingulatum Ben Woo
Tricholoma davisiae Andrew Parker	Tricholoma flavovirens Steve Trudell	Tricholoma focale Andrew Parker	Tricholoma fulvum Boleslaw Kuznik
Tricholoma imbricatum Michael Beug	Tricholoma inamoenum Andrew Parker	Tricholoma intermedium Andrew Parker	Tricholoma muricatum Steve Trudell
Tricholoma murrillianum Paul Kroeger	Tricholoma nigrum Steve Trudell	Tricholoma odorum Ben Woo	Tricholoma pardinum Andrew Parker
Tricholoma pessundatum group Michael Beug	Tricholoma populinum Andrew Parker	Tricholoma portentosum Andrew Parker	Tricholoma saponaceum Boleslaw Kuznik
Tricholoma sejunctum Steve Trudell	Tricholoma subluteum Ben Woo	Tricholoma sulphurescens Andrew Parker	Tricholoma sulphureum Steve Trudell
Tricholoma terreum group Michael Beug	Tricholoma triste Michael Beug	Tricholoma vaccinum Andrew Parker	Tricholoma venenatum Ben Woo
Tricholoma vernaticum Michael Beug	Tricholoma virgatum Steve Trudell	Floccularia albolanaripes Kit Scates Barnhart	Floccularia luteovirens Kit Scates Barnhart

Copyright to each photograph is held by the person named under the photograph.

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