Trial field key to the species of AGROCYBE in the Pacific Northwest

Prepared for the Pacific Northwest Key Council
By Carl A. Hermanson (Puget Sound Mycological Society) Feb. 1986
Copyright © 1986, 2002, 2003, 2017 Pacific Northwest Key Council
Photo copyright held by each photographer
Do not copy photos without permission

Reformatted and Revised by Coleman Leuthy & Maggie Rogers - Feb., 2003

Edited where specified by Ian Gibson in 2017




FRUIT BODIES small to medium in size. CAP convex to plane (1 to 10 cm. in diam.), surface dry to greasy/ sticky, glabrous, sometimes areolate, context white or brown, odor and taste sometimes farinaceous. GILLS adnate to sinuate, +/- decurrent, broad, close. SPORE COLOR medium brown to dark brown. STEM central, thin or moderately thick (2 to 10 cm long x 0.1 to 1.5 cm thick), smooth or roughly fibrillose. VEIL present or absent, sometimes well developed and leaving an annulus on mature stem, or forming an annulus, ring and/or zone. HABIT scattered to gregarious. HABITAT decaying hardwoods, debris, leaf litter, humus, chip dirt, bare soil, lawns, fields, roadsides, grasslands, open woods, and sand dunes. MICROSTRUCTURES cap cuticle cellular or with some cellular elements. Spores usually with an apical (germ) pore, surface smooth.


Key to Species







1a Forming partial veil, present or zone on the stem and/or leaving patches on the cap edge.

1b Partial veil absent or very rudimentary, i.e. no ring or zone on the stem and the cap edge typically naked.

2a Fruiting on decaying conifer or hardwood logs, chip debris, or leaf litter

2b Fruiting on humus, lawns, fields, or roadsides

[Editor’s note 2017 – Agrocybe praecox (see below) and Agrocybe putaminum (not included here but likely in the Pacific Northwest) can also occur on wood chips.]

3a (2a) Cap dark yellow brown when young becoming yellowish brown.

................................................................................Agrocybe acericola (Pk.) Sing.

CAP 3-7 cm broad, obtuse expanding to plane, with or without a low umbo; color when young dark yellow brown becoming yellowish brown in age; surface glabrous, moist, hygrophanous; margin even, opaque. ODOR & TASTE farinaceous. GILLS adnate with a decurrent tooth; crowded; color pallid to buff becoming brown. SPORE COLOR brown. STEM central, 5-10 cm long x 0.4- 1.5 cm thick, equal, hollow, fibrous, whitish becoming light blackish brown from base upwards, apex pallid and striate. VEIL membranous, cream color, well formed. HABIT solitary to scattered. HABITAT on decaying hardwood logs and debris, summer and fall. EDIBILITY unknown. MICROSTRUCTURES: Spores 8-10.5 x 5-6.5 um, apex snout-like with no apical (germ) pore, truncate. Pleurocystidia 40-50 x 12-22 um, clavate-mucronate to +/- utriform or with 1-3 apical projections. Cheilocystidia clavate.

3b Cap dark brown to dark reddish brown.

..................................................................Cyclocybe erebia (Fr.) Vizzini & Matheny (= A. erebia (Fr.) Kühner

 CAP 3-6 cm; convex becoming flattened with broad umbo; color dark brown to dark reddish brown; surface viscid, soon dry, glabrous; context brownish. GILLS subdistant; intervenose; broad, adnate to +/- decurrent; color pale brown then rust brown. SPORE COLOR very dark brown. STEM 3-7 cm long x 0.3-1 cm thick, equal, color pallid and pruinose near apex, dull brown lower down; surface fibrillose below and pruinose near apex. VEIL membranous, pallid, thin, tends to collapse, so ring sometimes disappears. HABIT scattered to gregarious. HABITAT in hardwoods and conifer woods, on bare soil or in leaf litter, edges of forests, forest tracks; summer to fall. EDIBILITY Unknown, DO NOT EAT IT. Too easy to confuse with poisonous species. MICROSTRUCTURES: Spores 11-15.5 x 5-6.5 um, apex snout-like with no apical (germ) pore. All basidia two-spored. Pleurocystidia 50-75 x 9-15 um, narrowly fusoid-ventricose, apex obtuse. Cheilocystidia 26-35 x 10-16 um, ventricose and apex broadly rounded or similar to pleurocystidia. EDITOR’S NOTE 2017 This species was moved to Cyclocybe in 2014. Cyclocybe erebia
Cyclocybe erebia
Ben Woo

4a (2b) Cap color cream at first, yellowish brown in age, odor and taste farinaceous; stem with white rhizomorphs. [see also habitat criteria in EDITOR’S NOTE below]

................................................................................Agrocybe praecox (Fr.) Fayod

 CAP 3-9 cm broad, obtuse to convex becoming plane or sometimes with a low broad umbo, cream to light brown at first, then yellowish brown in age, surface glabrous, sometimes areolate, soft to touch; context white, thin. ODOR and TASTE farinaceous. GILLS close, adnate to adnexed, broad; color pallid then light brown and finally dull dark brown. SPORE COLOR dark brown. STEM 3-10 cm long x 0.4 - 1.2 cm thick, equal, color whitish to pallid becoming brownish, apex often pruinose. VEIL submembranous, often as patches (appendiculate) on the edge of cap margin, disappearing with age. RHIZOMORPHS white at stem base. HABIT cespitose to densely gregarious or scattered. HABITAT of humus, chip dirt, lawns, fields, roadsides, open woods; spring to early fall. EDIBILITY: Edible. MICROSTRUCTURES: Spores 8-11 x 5-7 um, with an apical germ pore, truncate. Pleurocystidia 38-50 x 10-18 um, utriform. Cheilocystidia similar to pleurocystidia.Agrocybe praecox
Agrocybe praecox
Michael Beug

4b Cap white becoming buff tinted, at least on disc. [see also habitat criteria in EDITOR’S NOTE below]

.......................................Agrocybe molesta (Lasch) Singer or Agrocybe dura (Fr.) Singer

 CAP 3-10 cm, convex to plane, color white to pale yellowish cream becoming yellow brown tinged on disc; surface glabrous, often areolate with age; context solid and firm. TASTE slightly bitter. ODOR mushroomy. GILLS close, adnate to sinuate, broad, color white becoming +/- dark brown to purplish brown. SPORE COLOR light brown. STEM 4-10 long x 0.5-1.5 thick, equal; color whitish becoming somewhat brownish; apex +/- pruinose. VEIL white, forming a thin, superior, evanescent annulus or remains on the cap edge. HABIT scattered to gregarious. HABITAT on lawns, waste grassland, pastures, gardens, shrub borders, roadsides; spring to fall. EDIBILITY Edible, poor quality. MICROSTRUCTURES Spores 10-12 x 5-6 um, with an apical pore, truncate. Pleurocystidia 35-48 x 10-18 um, ventricose-pedicellate and apex broadly rounded. Cheilocystidia similar.Agrocybe molesta
Agrocybe molesta
Michael Beug

EDITOR’S NOTE 2017 Agrocybe molesta (Lasch) Singer may be a better name for this species in the Pacific Northwest than the name Agrocybe dura used in the original key. Kuo has addressed the place of Agrocybe molesta in the Agrocybe praecox group (drawing on Flynn 1990), maintaining that it is the only one in the group that is a devoted decomposer of grass litter, and the only one with spores as long as 10-14 microns. While acknowledging that a microscope may be needed for definitive identification, Kuo says, "To separate Agrocybe molesta (also known as Agrocybe dura) from Agrocybe praecox, field guides emphasize a suite of frustrating minor differences in physical features like the toughness of the stem, the tendency of the cap to crack in old age, the color of the cap, and the precise shade of brown displayed in the mature gills. But recent research has simplified things substantially for this species, allowing us to more or less ignore these differences and focus on the ecology: Agrocybe molesta is the only grass decomposer in the group, though it is variable in many of its physical features."

5a (1b) Rhizomorphs, if any, not well developed. Stem pale buff above, yellow-brown near base.

................................................................................Agrocybe pediades (Pers.: Fr.)

 CAP 1-6 cm, hemispherical to broadly convex; color whitish to dull yellow brown; surface glabrous, slightly viscid when moist; context thick, color whitish. TASTE farinaceous. GILLS adnate, seceding, broad, very pale brown becoming +/- rusty brown. SPORE COLOR dark brown. STEM 2-7 cm long x 0.15-0.3 cm thick, equal, tapering downward or with a slightly enlarged base; surface more or less fibrillose, furfuraceous, glabrescent; color pale yellow-orange above with yellowish brown near base. VEIL none. HABIT scattered to gregarious. HABITAT grassy areas, waste land, poor pastures, and sand dunes. EDIBILITY CAUTION. MICROSTRUCTURES: Spores 10-12 x 6-6.5 (7) um, with a distinct apical germ pore. Cheilocystidia present. Basidia 2 and 4 spored. NOTE: Other species names of A. pediades complex of related species include A. semiorbicularis (Bull.:Fr.) Fayod, A. subpediades (Murrill) Watling, and A. stepposa Scorcek. These species are two-spored with larger spores than A. pediades.Agrocybe pediades
Agrocybe pediades
Michael Beug

5b White rhizomorphs at base. Stem grading to orange-brown or dull greenish light brown on lower portion.

6a (5a) Cap 4-7 cm, stem apex off-white grading to orange-brown on lower stem.

................................................................................Agrocybe smithii H.E. Bigelow & Watling

CAP 4-7 (10) cm, convex expanding to plano-convex or plane at maturity, occasionally with a broad low umbo; color yellow brown to orange brown at first becoming yellow brown to medium brown in age; surface smooth, slightly greasy when moist, often becoming dry and breaking into little patches separated by deep cracks or crevices; context firm, white, 5-10 mm thick. ODOR & TASTE farinaceous and slightly bitter. GILLS adnexed, 4-8 mm broad, equal; dull grayish yellow to a pale orange brown becoming dull pinkish-orange brown in age. SPORE COLOR dull gray brown. STEM central, 4-7 cm long x 1-3 cm thick; base slightly enlarged to subclavate, apex off-white, grading to orange brown on lower stem; apex to mid-stem pruinose; lower surface innately fibrillose, often grooved, surface occasionally splitting into recurved scales; context white, firm, fibrous, with soft pithy center. VEIL None. RHIZOMORPHS white at stem base. HABIT gregarious in rings or troops. HABITAT mulch beds; spring to summer. EDIBILITY unknown. MICROSTRUCTURES: Spores 11.1-13.3 x 5.2-7 um, elliptical, smooth, apex truncated with apical germ pore. Pleurocystidia subcylindric, clavate to ventricose with obtuse apices and a narrow base, 27-45 x 12.6 um. Cheilocystidia similar to pleurocystidia.

6b Cap 0.8-1.5 (3.0) cm, stem apex white to off-white and dull greenish brown from midstipe to base.

................................................................................Agrocybe columbiana nom. prov. Rehner

CAP 0.8-1.4 (3) cm broad, convex to plano-convex when young, frequently plane to broadly wavy at maturity; margin incurved to decurved, edge somewhat rimose, eroded at maturity; surface moist to dry, smooth; color uniformly dull greenish brown; context firm, fleshy, white. ODOR farinaceous. TASTE strongly farinaceous. GILLS adnate to adnexed, close, ventricose; color rich orange brown. SPORE COLOR dull brown. STEM central, 1.0-1.5(2) cm long x 0.2-0.45 cm thick, round cross section; color white to off white at apex, dull greenish light brown from midstipe to base. Context fibrous, firm, solid, white. VEIL None. RHIZOMORPHS white, usually 1-3, thin. HABIT terrestrial, scattered to gregarious. HABITAT on native soils in grassy areas; spring and fall. EDIBILITY unknown. MICROSTRUCTURES: Spores 7.4-8.9 x 5.2-5.9 um, elliptical, thin walled, smooth, pale yellow, with inconspicuous germ pore. Pleurocystidia and cheilocystidia ventricose, rostrate.


GLOSSARY of terms found in this key:

areolate - marked with cracks or crevices

caulocystidia - cystidium-like cell on the stem

cheilocystidium - cystidium-like cell on the edge of a gill

cystidium - a large sterile cell

evanescent - only slightly developed or soon disappearing

farinaceous - texture or odor like fresh meal (flour)

fibrillose - hairy filaments, thin, threadlike

furfuraceous - texture like fine meal

glabrous - smooth, no scales or hairs

intervenose - gills having veins on surface extending various distances into the interspace, or crossing it to the next gill

pleurocystidia - cystidium-like cell on face of gill

pruinose - surface finely powdered or frosted

rhizomorph - strand or cord of compacted mycelium

rostrate - beaked

striate - minute radiating furrows or lines

ventricose - swelling out in the middle or at one side; inflated



  1. Flynn, Timothy, O.K. Miller Jr. 1990. Biosystematics of Agrocybe molesta and sibling species allied to Agrocybe praecox in North American and Europe. Mycological Research 94: 1103-1110.
  2. Hesler, L.R., and A. H. Smith, 1968. The North American Species of Pholiota. Hafner Publishing Co., New York, p385.
  3. Kuo, Michael. Accessed Feb. 8, 2015. Agrocybe molesta. Retrieved from the Web site
  4. Kuo, Michael. Accessed January 18, 2017. The Agrocybe praeocox cluster. Retrieved from the Web site
  5. McIlvaine, C., and C. Macadam, 1973. One Thousand American Fungi. Dover Publishing Inc., New York. (Reprint) pp271-3.
  6. Miller, O.K. Jr., 1979. Mushrooms Of North America. E.P. Dutton, New York, p200.
  7. Moser, M., 1983. Keys to Agarics and Boleti. The Whitefriars Press Ltd., Tonbridge, Great Britain, p289-291.
  8. Phillips, R., 1981. Mushrooms and Other Fungi of Great Britain and Europe. Pan Books Ltd., Cavaye Place, London, pp 168-70.
  9. Singer, R. 1977. The Agaricales in Modern Taxonomy. J. Cramer, New York.
  10. Smith, A.H., H.V. Smith, and N.S. Weber, 1979. How To Know the Gilled Mushrooms. Wm. C. Brown Publisher, Dubuque, Iowa, pp227-231.
  11. Watling, R., and N.M. Gregory, 1981. Census Catalogue of World Members of the Bolbitiaceae. Bibliotheca Mycologica Band 82, J. Cramer, New York.



Sincere appreciation is hereby expressed to: The late Dr. Daniel E. Stuntz for his guidance, Kit Scates for her encouragement, slides, and copies of data, and to Dr. Joe Ammirati and Steve Rehner for their consultation.




    A. acericola (Pk.) Singer 3a
    A. columbiana nom. prov. Rehner 6b
    A. dura (Fr.) Singer 4b
    A. erebia (Fr.) Kühner 3b
    A. molesta (Lasch) Singer 4b
    A. pediades (Pers.: Fr.) 5a
    A. praecox (Fr.) Fayod 4a
    A. semiorbicularis (Bull.:Fr.) Fayod 5a
    A. smithii H.E. Bigelow & Watling 6a
    A. stepposa Scorcek 5a
    A. subpediades (Murrill) Watling 5a
    C. erebia (Fr.) Vizzini & Matheny 3b


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