Trial Key to STEREUM in the Pacific Northwest

Prepared for the Pacific Northwest Key Council
by Ian Gibson, South Vancouver Island Mycological Society
Copyright © 2007, 2012, 2019 Pacific Northwest Key Council
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Key to Stereum

Species descriptions






Stereum hirsutum is common on hardwood and resembles the turkey-tail, (the polypore Trametes versicolor), but there are no pores on the undersurface. Stereum ochraceoflavum is also common and distinctive on hardwood twigs and branches. Stereum sanguinolentum grows on conifer wood and bleeds red fluid when cut. The nine Stereum species recorded for British Columbia, Washington, Oregon, and Idaho in Ginns & Lefebvre (1993) are described and distinguished.

The distinctions are sometimes not easy in practice. Welden (1971) despaired of differentiating Stereum complicatum and Stereum gaupatum from Stereum hirsutum because they were little different microscopically and morphological features were not dependable. Welden's solution was to synonymize the latter with the former (following Lentz).



1a Bleeds red liquid when cut

1b Does not bleed red liquid when cut

2a Growing on conifer wood

................................................................................S. sanguinolentum

(If description does not fit well, go to 3 as the other species are occasionally reported from conifer wood.)

2b Growing on hardwood or unknown wood

3a Thin fruitbody circular, inverted cup-shaped, or projecting bracket-like, upper surface with long whitish hairs, distinct concentric zones only when moist

3b Fruitbody projecting like bracket or shelf or with narrow base, with velvety hairs, upper surface zoned concentrically, or growing flat on wood with or without projection at upper surface

4a Orange to orange-buff underside when fresh, fruitbodies mostly bracket-like to shelf-like with broad attachment or in clusters

4b Ocher to brown or buff underside when fresh, or some fruitbodies have narrowed or stem-like attachment, or growing primarily flat (may project up to 2 cm at upper edge)

5a solitary or gregarious with some confluence, uncommonly shingled; cap flattened or wavy; cap tomentum thick, with concentric furrows

5b cespitose, confluent, often shingled; many caps strongly radially pleated (complicate – folded back on itself); tomentum scant or appressed, alternating bands of orange and brown

6a (4b) At least some fruitbodies with narrowed or stem-like attachment

6b Fruitbodies growing flat on wood or projecting up to 2 cm with broad-based attachment

7a fan-shaped to spoon-shaped fruitbody (pseudoacanthohyphidia absent)

7b oyster-shaped fruitbody (pseudoacanthohyphidia present)

8a (1b) growing on conifer wood

8b growing on hardwood or unknown wood

9a annual, one fruitbody layer in cross-section, common

9b perennial, with multiple layers visible in cross-section, rare especially on conifer wood

10a Growing on oak

10b Growing on other hardwood or unknown wood

11a Pseudoacanthohyphidia absent

11b Pseudoacanthohyphidia present (thin-walled hymenial element bearing 2-5 apical projections)



  Predominant form Typical hymenial color Bleeding & Staining Habitat Pseudo-acanthohyphidia
ochraceoflavum Inverted cup, bracket Ocher, buff - Hardwood, occ. conifer No
hirsutum Bracket Orange, buff Rarely reddens injured Hardwood, occ. conifer No
complicatum Strongly pleated bracket Orange, buff May redden injured Oak, hardwood, occ. conifer No
subtomentosum Fan, spoon, some with narrow attachment Ocher, buff Bleeds yellow Hardwood No
ostrea Oyster, some with narrow attachment Ocher, buff May bleed yellow or red Oak, hardwood, occ. conifer Yes
sanguinolentum Flat or bracket Ocher Bleeds red Conifer Yes
gausapatum Flat (folded radially), or pleated bracket Gray-brown, Red-brown, Ocher-brown Bleeds red Oak No
rugosum Flat Ochre, buff Bleeds red Hardwood, occ. conifer Yes





Stereum atrorubrum Ellis & Everh.

FRUITBODY fan-shaped or kidney-shaped, 1-3 cm across and long, leathery, thin, upper surface at first tomentose-downy, faintly zoned, when mature dull dark red, bald, and densely radiate-wrinkled; margin lobed and crisped; spore-bearing surface underneath yellow, becoming brick color when old, paler when dry, when mature the 3-5 concentric zones are more distinct and slightly elevated. FRUITING known only from the type specimen, on old logs in May in BC. MICROCHARACTERS spores up to 7 x 2-2.5 um present, but "may not belong for only 2 seen"; no cystidia, gloeocystidia, or conspicuous conducting organs seen; composed of an intermediate layer of longitudinal, densely arranged, thick-walled, rigid hyphae 3-3.5 um wide, bordered on the upper side by an opaque brown layer that gives the color to the cap, and on the lower side hyphae curving into a hymenial layer. REMARKS too rare and insufficiently characterized to include in the key.

Stereum complicatum (Fr.) Fr.    crowded parchment

FRUITBODY up to 1.5 cm wide and projecting up to 1.5 cm, fan-shaped or semicircular, or flat with a part bent outward to form caps, strongly radially pleated so that they can be called complicate (or in some fruitbodies more wavy), lobed, cespitose, strongly confluent, and often imbricate (shingled), leathery-rigid, thin, the upper surface pinkish to orange-buff or grayish with whitish margin, scantily tomentose to bald, with alternating concentric zones of orangish and brownish that fade; flat part and underside of caps (spore-bearing surface) orange to buff, more or less smooth; may bruise red. FRUITING on dead hardwood twigs and stumps, especially oak; July to January, fruitbody overwinters, has also been recorded on Picea (spruce), Pseudotsuga (Douglas-fir), Thuja, associated with a white rot. MICROCHARACTERS spores 5-6.5 x 2-2.5 um, cylindric to slightly curved, smooth, colorless; pseudocystidia thin-walled at tip but otherwise thick-walled, sharp-tipped hyphidia presumably present, but not pseudoacanthohyphidia. REMARKS the name means 'complicate' (bent upon itself), indicating its pattern of cap folding. Stereum hirsutum and Stereum gausapatum have a rather thick fruitbody (0.05-0.15 cm), sometimes more, whereas Stereum complicatum is usually thinner, usually up to 0.05 cm; for the other differences from Stereum hirsutum see the key; Stereum gausapatum has pseudocystidial walls less than 1.5 um thick and is restricted to oak. ILLUSTRATIONS Phillips, Lincoff (1995)

Stereum gausapatum (Fr.) Fr.

FRUITBODY growing flat on wood or bent outward to form caps that project up to 2 cm, forming patches up to several decimeters across, caps usually fused in rows, larger caps pleated radially, fruitbody up to 2 mm thick, consistency elastic-tough, upper surface of caps gray to rust brown, appressed-tomentose in narrow zones to bald, margin sharp, crisped, paler than the rest of the cap; flat part and underside of caps (spore-bearing surface) smooth to tuberculate (bumpy), often folded radially, color gray-brown, red-brown, or ocher-brown, margin of spore-bearing area paler than the rest; fresh fruitbodies when cut exude a red fluid which becomes brown, bruised areas reddish then dark violet or blackish. FRUITING generally restricted to Quercus (oak), on dead wood with and without bark, on standing and fallen trunks, and attached or fallen branches, often covering entire trunks and branches for meters, some reports on other hardwoods, and also reported on Pseudotsuga menziesii (Douglas-fir). MICROCHARACTERS spores 6-9(10) x 3.5-4.5 um, elliptic-cylindric, smooth, iodine reaction very weakly positive, colorless; basidia 2-4-spored; pseudocystidia thin-walled at tip but otherwise fairly thick-walled, colorless to yellowish and with a grainy to oily content, 5-10 um wide, often more than 150 um long, sharp-tipped hyphidia 20-30 x 2-4 um, projecting slightly and easily observed in thin sections, pseudoacanthohyphidia absent; clamp connections absent. REMARKS name is from 'gausapa', meaning 'shaggy, woollen cloth or garment'; Stereum gausapatum is restricted to Quercus (oak), while other Stereum species can grow on oak, but a Stereum specimen on oak is most likely to be S. gausapatum; Stereum gausapatum can be distinguished from S. hirsutum, S. complicatum, and S. subtomentosum on the basis of its average pseudocystidial wall thickness less than 1.5 um. ILLUSTRATIONS Breitenbach & Kränzlin

Stereum hirsutum (Willd.: Fr.) Gray    false turkey-tail, hairy Stereum

FRUITBODY growing flat on hardwood, and also forming caps that project up to 3 cm, semicircular to fan-shaped, broadly attached, usually fusing to form imbricate (shingled) rows, up to 2 mm thick, consistency elastic, tough, cap surface woolly-hairy, zoned circumferentially, yellow-orange to reddish brown with gray-whitish tomentum, fading to gray-ocherish and bald when old, sometimes greenish from algae, margin wavy and somewhat lighter in color; flat part and underside of caps (spore-bearing surface) bright yellow-orange to brown-orange (when old gray-brown), smooth or may be slightly tuberculate (bumpy), the margin distinct and when actively growing it is whitish; flesh very rarely turning red when bruised. FRUITING common on dead wood of hardwoods with and without bark, on standing and fallen trunks, and on attached and fallen branches, often covering entire trunks and branches for meters, has been reported occasionally on conifers; associated with a white rot. MICROCHARACTERS spores 5-8 x 2-4 um, elliptic-cylindric, smooth, weak amyloid reaction, colorless; basidia 4-spored; pseudocystidia abundant, not or rarely projecting, 7-10 um wide and often more than 100 um long, thick-walled except at the tip, in the outer part filled with oily content, sharp-tipped hyphidia numerous, 20-30 x 2-4 um, projecting slightly and easily observed microscopically, pseudoacanthohyphidia absent; clamp connections absent. REMARKS ‘hirsutum’ means 'hairy'; this species with some similar members is said to form the Stereum hirsutum complex (S. hirsutum, S. complicatum, S. subtomentosum, and S. gausapatum in the Pacific Northwest), the key distinguishes S. hirsutum from S. complicatum; Stereum subtomentosum differs microscopically from Stereum hirsutum (having pseudoacanthohyphidia for instance) and has buff underside and slightly larger caps (1-7 cm broad) that are more prominently zoned and usually form individual brackets rather than fusing; a Stereum specimen on oak is most likely to be Stereum gausapatum: the latter has a buff to gray-brown spore-bearing surface instead of yellow to pale orange, it bruises red, caps are radially wrinkled, and unlike other members of S. hirsutum complex it has pseudocystidial wall thickness less than 1.5 um; for the differences from S. ochraceoflavum see that species; Hymenochaete tabacina can be similar in shape and color, but its tissue blackens in KOH; Trametes versicolor is superficially similar to Stereum species but has pores underneath, easily seen with a hand lens. ILLUSTRATIONS Lincoff (1995), Lincoff (1981), Arora, Breitenbach & KränzlinStereum hirsutum
Stereum hirsutum
John Davis

Stereum ochraceoflavum (Schwein.) Peck

FRUITBODY shallowly cup-shaped with concave spore-bearing surface facing downward from underside of wood, when young sometimes suspended from midpoint of a circular cap surface, often growing together to form a row or rows on twigs and small branches, also growing flat on undersides of the wood and extending outwards or forming brackets, caps up to 1.0 cm across and extending up to 0.5 cm from the substrate, up to 0.4 mm thick, consistency somewhat tough, elastic, pliant; upper surface of caps finely silky-hairy-tomentose with loose hairs that point predominantly toward margin, indistinctly zoned, hairs gray-whitish to ocher-whitish, surface sometimes colored greenish by algae, cap margin sharp-edged, fringed; flat part and underside of caps (spore-bearing surface) brown-ocher, gray-ocher, cream-buff, or pale orange-yellow, smooth, wavy, tuberculate (bumpy). FRUITING common on dead twigs and branches of hardwoods, especially Quercus (oak), rare reports on conifers, associated with a white rot. MICROCHARACTERS spores 5.5-9 x 1.5-3 um, cylindric to elliptic, smooth, amyloid, colorless; basidia 4-spored; pseudocystidia 80-110 x 5-7 um, thick-walled, acute-tipped hyphidia 30-35 x 3-4.5 um, pseudoacanthohyphidia absent; septa without clamp connections. REMARKS distinguished from S. hirsutum complex (Stereum hirsutum, Stereum complicatum, S. subtomentosum, and S. gausapatum) by its 1) thinner, more pliant cap, 2) tomentum of long white hairs pointing toward the margin, as opposed to tomentum that is some shade of brown and when old yellow-gray, 3) its tendency to favour twigs and prunings, (while S. hirsutum complex is also found on trunks, in crevices, and on thick branches), 4) lack of a compact brown cutis about 50 um thick underlying the tomentum in S. hirsutum complex, 5) duller color of hymenium in relation to S. hirsutum and S. complicatum. ILLUSTRATIONS Breitenbach & Kränzlin; Arora (as Stereum striatum var. ochraceoflavum)

Stereum ostrea (Blume & T. Nees: Fr.) Fr.     false turkey-tail

FRUITBODY oyster-shaped with a narrowed attachment, or fan-shaped, or semicircular and bracket-like, or occasionally bent outward from a flat growth on wood, up to 10 cm across, tough, leathery, up to 1 mm thick, caps often overlapping, upper surface of cap light buff to rusty brown, or drab to grayish, often green from algae, when fresh with concentric zones of brown and rust, with felty tomentum; underside of caps (spore-bearing surface) buff to ochraceous or dingy light brown or grayish, the surface smooth and often wavy, when damaged bleeding or not, the fluid may be red or yellow turning red. FRUITING on logs and stumps of hardwoods, especially oak. MICROCHARACTERS spores 4-7 x 2-3 um, narrowly elliptic to cylindric, smooth, colorless; pseudocystidia thick-walled, sharp-tipped hyphidia presumably present, pseudoacanthohyphidia thin-walled. REMARKS name means 'oyster'; many of the collections reported as this species are suspected by Ginns & Lefebvre (1993) to represent S. subtomentosum, which is spathulate to fan-shaped, less brown in color, and lacks pseudoacanthohyphidia. ILLUSTRATIONS Phillips, Lincoff (1995)

Stereum rugosum Pers.: Fr.

FRUITBODY growing flat on wood or sometimes bent outward to form narrow shelf-like caps that may form imbricate (shingled) clusters, forming patches up to several decimeters across, leathery-tough to hard, at first in rounded patches, usually with a loosening margin, caps when present narrow, wavy to lobed, rarely projecting more than 1cm, the upper surface at first finely tomentose and grayish, soon becoming bald and dark brown, finally blackish; margin white to pale ochraceous and rounded; spore-bearing outer surface (or undersurface of caps) smooth, tuberculate (bumpy) to wavy, with distinct margin, pale ochraceous to buff or grayish, often with black spots when old, bleeding when cut or touched while fresh, fluid first reddish, but soon blackish brown; in section, the multiyear fruitbody distinctly layered, each layer clearly defined by a thin dark line, total up to 0.2 cm thick. FRUITING rare, on dead, standing or fallen wood of hardwoods, with and without bark, also reported from Abies (fir), Picea (spruce) and Pseudotsuga (Douglas-fir). MICROCHARACTERS spores 7-12 x 3-4.5 um, narrowly elliptic to cylindric, slightly bent, smooth, amyloid, colorless; basidia 4-spored; pseudocystidia 5-12 um wide, usually more than 100 um long, thick-walled, except for the apical part, slightly projecting, smooth, more or less constricted, colorless to yellowish, with oily content, sharp-tipped hyphidia also occur, pseudoacanthohyphidia easily observed, 25-35 x 3-4 um, projecting slightly beyond the basidia, clamp connections absent. REMARKS ‘rugosum’ means 'with wrinkles'. ILLUSTRATIONS Breitenbach & Kränzlin

Stereum sanguinolentum (Alb. & Schwein.: Fr.) Fr.     bleeding conifer parchment

FRUITBODY growing flat on conifer wood in patches with slightly loosening margins, or bent outwards to form shelf-like cap, or with distinct caps; often growing together and covering large areas several decimetres across on the lower side of logs, separable from wood, up to 0.1 cm thick, leathery-tough; cap when present narrow and mostly projecting less than 1.0 cm, often fused laterally, wavy, and lobed, or as dense, imbricate (shingled) clusters, the upper surface finely tomentose to hairy, grayish white to brownish, soon becoming bald in zones and exposing reddish brown or orange-brown bands, when old almost completely bald, blackish; flat part and underside of caps (spore-bearing surface) smooth, wavy to wrinkled or tuberculate (bumpy), ocherish to buff , often with a hint of violet, when old dark brown, when fresh strongly bleeding red fluid when cut, bleeding parts drying dark brown; margin of spore-bearing area distinct, narrow, white to pale buff, wavy. FRUITING on dead wood of conifers, with and without bark, associated with a white rot; annual, rarely perennial. MICROCHARACTERS spores 6.5-7.5 x 2.5-3 um, elliptic-cylindric, smooth, amyloid, colorless; basidia 2-4-spored without basal clamp connection; pseudocystidia thick-walled except for in the apical part, projecting very slightly above the basidia, filled with oily to grainy, pale brown content, colorless in the hymenium, in the basal part yellowish and 3-6 um wide, in the upper part 4-10 um wide, usually longer than 100 um, sharp-tipped hyphidia presumably present, pseudoacanthohyphidia 30-40 x 2-3.5 um, thin-walled, with knob-like to thorn-like tips; septa without clamp connections. REMARKS the only Stereum species likely to be growing on conifer wood, other bleeding species grow on hardwoods. ILLUSTRATIONS Breitenbach & Kränzlin, Lincoff (1995) (as Haematostereum sanguinolentum)

Stereum subtomentosum Pouzar

FRUITBODY single or more often in dense shingled clusters, projecting up to 5 cm, and 3-7 cm long in fused fruitbodies, fan-shaped to spathulate (somewhat like a spoon with rounded fruitbody and narrowed stem-like base), leathery and tough, thin, with a distinctly tapering and often short stem-like base, or more broadly attached, margin thin and often lobed or wavy, upper surface with a soft velvety tomentum, yellowish gray to pale brown in narrow concentric zones, when old some specimens more hirsute (hairy) and gray with a greenish tint at the base due to algae, eventually nearly bald, spore-bearing (lower) surface smooth, tuberculate (bumpy) or undulating, light beige to ochraceous, exuding yellowish fluid when cut or wounded in fresh condition, margin lighter in color. FRUITING annual, on wood of Alnus (alder) and other hardwoods. MICROCHARACTERS spores 5.5-8 x 2-3 um, cylindric to narrowly elliptic, often slightly bent, smooth, amyloid, colorless; basidia 4-spored; pseudocystidia thick-walled except near tip, often constricted or with an appendix at the tip, projecting slightly above the basidia and with yellowish content, 4-12 um wide, usually longer than 100 um; sharp-tipped hyphidia numerous, projecting slightly above the basidia, about 35-40 x 4-5 um, pseudoacanthohyphidia absent; septa without clamp connections. REMARKS probably often misidentified as Stereum ostrea which has an oyster-like (as opposed to fan-shaped to spoon-shaped) fruitbody and more brownish color. ILLUSTRATIONS Breitenbach & Kränzlin





cespitose - growing in tufts or close clusters from a common base, but not grown together

corticioid - as used by Ginns (1993) includes resupinate taxa with smooth, rough, or toothed spore-bearing surfaces but not resupinate polypores (refers to a general resemblance that certain typically spread out, thin fruitbodies have to bark); a term that covers many of the same fruitbodies as the "crust fungi"

hymenial - refers to the hymenium, the spore bearing surface, which faces outward when the corticioid fungus grows flat on the wood, or covers the underside of corticioid caps when they form

hyphidium (plural hyphidia) - a modified terminal hypha in the hymenium

pseudoacanthohyphidium (plural pseudoacanthohyphidia) - thin-walled hymenial elements that bear a few (2-5, rarely up to 10) apical projections; Stereum ostrea, Stereum rugosum, and Stereum sanguinolentum are members of the subgenus Aculeatostereum which have pseudoacanthohyphidia: (also known as pseudoacanthophyses, aculeate-tipped basidioles, acanthocystidia, and acanthohyphidia, by different authors, the last term also used for acanthophyses - with projections throughout their length - that occur in subgenus Acanthostereum not found in North America), (Chamuris(1985b))

pseudocystidium (plural pseudocystidia) - sterile structure that arises deep to the subhymenium and protrudes into the hymenium, true cystidia being directly associated with the hymenium and having their origin in the subhymenium; cystidium derived from a conducting element, filamentous to fusoid, oily contents, embedded or not projecting; in practice the differentiation between the cystidia and pseudocystidia is sometimes difficult and different authors may refer to the same structure as a cystidium or a pseudocystidium

lignicolous - living on wood

mycorrhizal - having particular symbiotic relationship with the roots of a seed plant, the rootlets of the plant being covered or permeated by the mycelium of the fungus

resupinate - lying flat on what fungus is growing on, without a stem or well-formed cap, with the gills or pores facing outward

tuberculate - with low bumps, larger than what would be considered warts





  1. Arora, David. 1986 Mushrooms Demystified Second Edition. Ten Speed Press, Berkeley.
  2. Breitenbach, J., Kränzlin, F. 1986. Fungi of Switzerland Volume 2 Non-gilled Fungi. Edition Mykologia Lucerne.
  3. Burt, E.A. 1920. The Thelephoraceae of North America XII. Stereum. Ann. Missouri Bot. Gard. 7: 81-248.
  4. Chamuris, George P. 1985a. On distinguishing Stereum gausapatum from the "S. hirsutum complex". Mycotaxon 22: 1-12.
  5. Chamuris, George P. 1985b Infrageneric taxa in Stereum, and keys to North American species. Mycotaxon 22: 105-117.
  6. Eriksson, J., K. Hjortstam & L. Ryvarden. The Corticiaceae of North Europe. Volume 7. 1279-1449. 1984. Fungiflora, Oslo.
  7. Gibson, Ian, E. Gibson, B. Kendrick. September 2006. MatchMaker: Mushrooms of the Pacific Northwest. Compact Disc Version 1.21.
  8. Ginns, James, M.N.L. Lefebvre. 1993. Lignicolous Corticioid Fungi (Basidiomycota) of North America Systematics, Distribution, and Ecology. The Mycological Society of America Mycologia Memoir No. 19. American Phytopathological Society Press. St. Paul, Minnesota.
  9. Jülich, W., J.A. Stalpers 1980. The Resupinate Non-poroid Aphyllophorales of the Temperate Northern Hemisphere. North-Holland Publishing Company, Amsterdam, Oxford, New York.
  10. Lincoff, Gary. 1981. Simon and Shuster’s Guide to Mushrooms. Simon & Shuster, New York.
  11. Lincoff, Gary. 1995. National Audubon Society Field Guide to North American Mushrooms. Knopf, New York.
  12. Phillips, Roger. 1991. Mushrooms of North America. Little, Brown, & Co., Boston.
  13. Welden, A.L. 1971. An Essay on Stereum. Mycologia 63: 790-799.




 STEREUM Pers.  
    S. atrorubrum Ellis & Everh.  
    S. complicatum (Fr.) Fr. 5b
    S. gausapatum (Fr.) Fr. 10a, 11a
    S. hirsutum (Willd.: Fr.) Gray 5a
    S. ochraceoflavum (Schwein.) Peck 3a
    S. ostrea (Blume & T. Nees: Fr.) Fr. 7b
    S. rugosum Pers.: Fr. 9b
    S. sanguinolentum (Alb. & Schwein.: Fr.) Fr. 2a, 9a
    S. subtomentosum Pouzar 7a


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