Chlorociboria aeruginascens: Green Elfcup Identification & More

Chlorociboria aeruginascens, also known as The Green Elfcup or The Blue-Green Cup Fungus, is rather unique and fascinating fungus from the small genus of Chlorociboria. This beautiful saucer-shaped fungus is more often characterized by the blueish green “rot” it leaves behind on the hardwoods it grows on than by its own morphologic features.(1)

C. aeruginascens was initially described by the Finnish mycologist William Nylander who gave it the name Peziza aeruginascens. It was not until 1957 that a group of American mycologists (C.S. Ramamurthy, R.P. Korf, and L.R. Batra) would transfer the species to the Chlorociboria genus.

The etymology of this specie’s specific epithet, aeruginascens, refers to the blueish green “rot” or “stain” that occurs to wood colonized by this fungus. It’s important to note, however, that this “rot” is not a form of “true” wood rot but rather a type of “soft rot,” arising from slight erosion in the wood cells colonized by the fungus. In fact, hardwoods like oak, ash, poplar, and aspen that exhibit this distinctive blue green “rot” or “stain” are highly prized and have been historically utilized by woodworking artisans for centuries. Examples include the Italian Renaissance tarsia, an intricate form of marquetry, and English Tunbridge ware from Kent, encompassing small wooden boxes inlaid with splinters and veneers of the green-stained wood, forming intricate patterns and designs. Even in the 21st century, scientists from institutions such as the U.S. Center for Forest Mycology Research and the Forest Products Laboratory of the U.S. Forest Service continue to investigate techniques for introducing staining fungi like C. aeruginascens into wood with the aim of generating value-added materials from less valued wood species for the woodworking industry.(2)

Synonyms for this species include: Chlorociboria aeruginascens, Chlorosplenium aeruginascens, Peziza aeruginascens.

Identification and Description

As previously noted, the identification of this fungus is primarily achieved through the detection of the bluish green “discoloration” that remains as in many instances, you don’t see the actual fruiting. Nonetheless, below are given the macro- and micromorphological characteristics of Chlorociboria aeruginascens.

Fruiting Body: The fruiting body of C. aeruginascens measures 3 to 10mm in diameter. Young specimens start out as cup or goblet-shaped, becoming flat or disclike with slightly elevated and wavy margins as they age. The upper fertile surface (top) of the fruiting body is bright to pale blue-green or turquoise, sometimes with a yellowish or orange-yellow tint developing in age, and smooth. While the underside of the fruiting body is paler blue green in color, becoming darker with age but never yellowing, and is felty is texture rather than smooth.
Flesh: Flesh of this species is thin and bluish green.
Stem: The stem is short and rather narrow, measuring only 3-6mm in length and 0.5-1cm in width. It is concolorous with the cap and has similar felty texture as the underside of the cap. The attachment of the stem to cap is often slightly off center.
Spores: The spores of this species measure 6-10 by 1.5-2 µm. They are spindle-shaped or elongated, smooth, with an oil droplet at each end.
Spore print: This species does not leave behind a spore print.
Smell: Non-distinctive.
Edibility: The edibility of this species remains uncertain; nevertheless, its exceedingly small size makes it improbable for it to be regarded as an edible species.
Habitat and Ecology: This species grows scattered or gregarious (with several arising from a common base) on dead or barkless hardwoods such as oak, hazel, beech, ash, poplar, and aspen.
Range/Geographic Distribution: This is a widely distributed species but hard to spot due to its small size. It can be found in Europe, Asia, North America, South America, and Australia. In the United States, it inhabits regions east of the Great Plains and west of the Sierra Nevada and Cascade Mountain Ranges.
Fruiting Season: As mentioned previously, evidence of this mushroom’s presence can be found year-round as green-stained wood. However, the fruiting bodies themselves can appear year-round as well but are often found in winter, and early spring.


The only other species that resembles Chlorociboria aeruginascens is the Turquoise Elfcup (Chlorociboria aeruginosa). C. aeruginosa is very similar (so much so that it is practically identical to the naked eye) and is also widely distributed. However, it is generally smaller (less than 5 mm broad), has a shorter, more central stalk, and orange-yellow flesh. Furthermore, C. aeruginosa has larger spores. (C. aeruginosa: 9-15 X 1.4-2.8 µm vs. 6-10 by 1.5-2 µm for C. aeruginascens.)


In the present day, researchers are exploring alternative applications for the blue green naphthoquinone pigment, Xylindein, found in Chlorociboria. The potential uses for this pigment encompass inhibiting seed germination, safeguarding wood from termite damage, eradicating algae, and even contributing to anti-cancer efforts.


Chlorociboria aeruginascens (Blue Stain). In: Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi. 2nd ed. Berkeley: Ten Speed Press; 1986. p. 878.

Thomas J. Volk, Jessie Micales Glaeser. Univeristy of Wisconsin Plant Teaching Collection. 2008. Chlorociboria aeruginascens, the green stain fungus.

Chlorociboria aeruginascens MushroomExpert

Chlorociboria aeruginascens (Nyl.) Kanouse ex C S Ramamurthi, R P Korf & L R Batra – Green Elfcup

Gary Emberger. Messiah University. Chlorociboria aeruginascens. 

Stevens MW& F. California Fungi: Chlorociboria aeruginascens

#166: Chlorociboria spp., Green Stain Fungi. Fungus Fact Friday. 2016

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