Summary:
Leucocoprinus birnbaumii is characterized by 1) a bright yellow, striate, dry, powdery to scaly cap, 2) free crowded yellow gills, 3) a yellow, dry, powdery stem with a yellow ring, 4) a white spore deposit, and 5) growth in flower pots or planter boxes. Some consider this as var. luteus of Leucocoprinus cepistipes. It is fairly common in the Pacific Northwest.

Cap:
2.5-6cm across when expanded, oval becoming broadly conic or bell-shaped, then eventually umbonate or flat and finally drooping; bright yellow to greenish yellow or pale yellow, "the center sometimes brown or buff", "fading quickly after it matures or becoming browner"; dry, powdery, mealy, and/or minutely scaly, usually scalier and less powdery when old, margin conspicuously striate nearly to center when mature, (Arora), 3-6cm, bell-shaped, becoming broadly conic to nearly expanded with prominent umbo, fragile; "lemon chrome" to "picric yellow", the disc often "yellow ochre", "covered by fine fibrillose (almost powdery), often recurved squamules which are easily removed, disc smooth or rough and breaking up into scales only at maturity", rimose-striate at margin, (Smith, H.V.), 1-6cm across, conic with margin incurved at first, aging in a day to flat with central umbo and finally sagging, (Sieger)

Flesh:
very thin; yellow, (Arora)

Gills:
free, crowded; yellow or pale yellow, (Arora), free from stem but attached to a ring, crowded; pale yellowish white, edges bright yellow; edges fimbriate [fringed] under a lens, (Smith, H.V.), free, close, in 1-3 tiers; pale yellow; edges even to finely fringed, (Sieger)

Stem:
3-10cm x 0.15-0.5cm, usually slender and widened somewhat at or toward base; yellow; dry, smooth or powdery like cap, (Arora), 4-8cm x 0.15-0.5cm, widened to base and 0.6-0.8cm wide there, hollow, stuffed; "covered by a bright lemon yellow powder, darker and orange-yellow on base", base pale yellowish white; base nearly bald when old, (Smith, H.V.), 2.5-8cm x 0.15-0.6cm, base widened, stem stuffed becoming hollow; bright yellow, fading when old; covered with yellow powder, (Sieger)

Veil:
yellow, forming small, superior, collar-like ring on stem that may disappear, (Arora), ring on upper third of stem, cottony-fibrillose, bright lemon yellow, probably movable, evanescent [fleeting], (Smith, H.V.), ring cottony-fibrous, yellow, perhaps movable, not persistent, (Sieger)

Odor:
not distinctive (Smith, H.V.)

Taste:
not distinctive (Smith, H.V.), mild with bitter aftertaste (Sieger)

Microscopic spores:
spores 8-13 x 5-8 microns, elliptic, smooth, dextrinoid, thick-walled, with apical germ pore, (Arora), spores 8-11 x 5-7 microns, oval-elliptic, thick-walled, brown in Melzer''s reagent; basidia 4-spored, clavate; pleurocystidia absent, cheilocystidia 24-80 x (5)9-21 microns, "fusoid-ventricose with obtuse apex, mucronate or with a more elongated neck, sometimes narrowly fusiform"; cap cuticle cellular, the cells irregular and sometimes +/- Y-shaped, mostly subspherical or short-cylindric and readily separable, often borne in +/- upright chains, cells 7-28 microns in diameter, (Smith, H.V.), spores 8-11 x 5-7 microns, oval-elliptic, dextrinoid, with a germ pore; pleurocystidia absent, cheilocystidia clavate to ventricose; cap cuticle "cellular, shape irregular, often in upright chains but not forming a trichodermium", (Sieger); clamp connections absent from cap cuticle and basidia, (Breitenbach), spores 7.7-10.5 x 5.9-7.3 microns, dextrinoid, metachromatic; pseudoparaphyses 16.5-22.1 x 10.5-12.8 microns, "narrowly utriform to narrowly clavate, lacking a pedicel, often somewhat angular"; cap covering "a confluent layer of terminal cells when young, disarticulating into scales and/or patches revealing short, inflated to cylindrical, loosely attached cylindrical, H-, T- to L-shaped contextual elements", terminal elements ascending to somewhat repent conglomerations of 32.5-155.0 x 7.5-18.8 microns, "flexuous cylindrical to somewhat narrowly lageniform to rarely elongate clavate terminal", (Birkebak)

Spore deposit:
white (Arora)

Notes:
There are collections from BC at Pacific Forestry Centre and the University of British Columbia. Collections were examined from WA (Birkebak(1)), and it is found in CA (Desjardin). There are collections at the University of Washington from WA, ON, and LA.

EDIBILITY

poisonous to some people, according to some sources, (Arora)

Synonyms and Alternate Names:
Lepiota lutea (Bolton) Quel.
Leucocoprinus luteus (Bolton) Locq.