Green Elf Cups

Decomposed aspen wood stained blue by fungus.
Decomposing wood stained blue-green is often the only evidence of the presence of Chlorociboria aeruginascens.


There is an extraordinary abundance of colorful fungi in the woods at this time of the year sprouting from dead logs, from under leaves, and through duff and moss. They come in reds, pinks, yellows, cream, white, buff. Some are the color of coffee dried at the bottom of the cup, others look like chocolate velvet. Colors may be solid or they may be zoned in concentric rings There are species that ooze orange sap when cut. And there are smells, too, from fragrant spice to anise and peppery to earthy. Some are sweet and others, like stink-horn, smell like rotting meat. The sizes of the fruiting bodies vary tremendously, too. There are giant puffballs 20 cm in diameter to tiny parasol mushrooms barely 2 mm tall growing on conifer needles. But most fungal activity goes un-noticed until fruiting bodies appears or in the case of some wood rots a tree or a barn collapses.

One fungus, known as “Green Stain” and “Green Elf Cups” (Chlorociboria aeruginascens) is easily noticed even when not in fruit. This is because Chlorociboria aeruginascens colors the wood it is decomposing to a rich blue-green color. The piece of wood shown at the top of the page is an aspen log that is thoroughly colonized by Green Elf Cups. The fungal mycellium of Green Elf Cups has a very strong pigment that stains wood blue. This is not the same discoloration as that caused by Blue Stain Fungus (Grosmannia clavigera) which infects living pine trees. Green Elf Cups fungus grows in dead wood including recently cut lumber. As the mycellium grows through the wood it turns blue from pigments secreted by the fungus. The color is produced by xylindein, a naphthoquinone, which the fungus secretes and probably inhibits the growth of other organisms. High levels of sucrose in the wood promote faster growth of the fungus. The staining or spalting can be a problem of its own for timber sales as the wood is generally regarded as less valuable. There is an exception made for some blue stained wood which is used for inlaid woodwork such as intarsia.

It is rare for Green Elf Cups to fruit except after long periods of rain so to find them is special. Most of the time the mycellium just grows throughout the wood staining it blue. Below are photos of Green Elf Cups fruiting bodies on a decomposing aspen logs. It had been a very rainy few days and the log itself rests in a damp spot in the forest. If you look closely at the first photo you will see a tiny snail just to the right of the largest fruiting body on the the left end. The snail is full sized and might be a species in the genus Vertigo. I suspect it was eating some of the Green Elf Cups as there are small holes in one.


Blue Stain Fungus
Green Elf Cups (Chlorociboria aeruginascens) on a fallen decomposing aspen log.


Green Elf Cups (Chlorociboria aeruginascens) on a fallen decomposing aspen log.
Green Elf Cups (Chlorociboria aeruginascens) on a fallen decomposing aspen log that is also very strongly stained.


The fruiting body of Chlorociboria aeruginascens appears in the late summer and fall especially after abundant rains. It starts out as a cup-shaped disc bit soon flattens out and about 2 to 5 mm across on a short 1 to 2 mm long stem centrally positioned or a little off-center. The surfaces of the fruiting body are smooth and without any hairs or other surface projections. When not in fruit the green stained wood is a reliable indicator of its presence at any season. The substrate is soft, decayed wood (logs, branches, stumps) often with the bark falling off. It is commonly found in aspen, willow, maples, birch, oak, and some conifers. Woods with high sugar contents are produce faster and more rapid growth of the fungus.

Kingdom: Fungi
Division: Ascomycota
Subdivision: Pezizomycotina
Class: Leotiomycetes
Order: Helotiales
Family: Helotiaceae
Genus/species: Chlorociboria aeruginascens

Range and Distribution
Chlorociboria aeruginascens is widely distributed in forests across North America including Mexico and the Caribbean islands, also South America, Europe, Asia, Australia, and Africa.

References Consulted
Blanchette, R. A.; Wimering, A. M.; and Baumeister, M. (1992). The Use of Green-Stained Wood Caused by the Fungus Chlorociboria in Intarsia Masterpieces from the 15th Century. Holzforschung 46:225-232.

Johnston, D. R. and Park, D. (2005). Chlorociboria (Fungi, Helotiales) in New Zealand. New Zealand Journal of Botany, Vol. 43: 679-719.

Rice, A. V and Langor, D. W. (2009). Mountain pine beetle-associated blue-stain fungi in lodgepole x jack pine hybrids near Grande Prairie, Alberta (Canada). Forest Pathology 39:323–334.

Robinson, S. C.; Tudor, D.; Snider, H.; and Cooper, P. A. (2012). Stimulating growth and xylindein production of Chlorociboria aeruginascens in agar-based systems. AMB Express. 2012; 2:15. doi:10.1186/2191-0855-2-15.

Robinson, S. C.; Weber, G.; Hinsch, E.; Gutierrez, S. M. V.; Pittis, L.; and Freitas, S. (2014). Utilizing Extracted Fungal Pigments for Wood Spalting: A Comparison of Induced Fungal Pigmentation to Fungal Dyeing. Journal of Coatings Volume 2014, Article ID 759073, 8 pages.

Seaver, F. J. (1951). The North American Cup-fungi (Inoperculates). New York, Published by the Author, 511 pages.

Tudor, D. (2013). Fungal Pigment Formation in Wood Substrate. A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy, Faculty of Forestry University of Toronto.

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