Chlorociboria aeruginascens

Scientific name:  Chlorociboria aeruginascens (Nylander)
Kanouse
Derivation of name:  Aerug- means "blue-green, green" and
ascens means "becoming" so that aeruginascens means
"becoming green."
Synonyms:  Chlorosplenium aeruginascens (Nyl.) P. Karst
Common name(s):  Blue stain; green stain; Blue-green wood
stain
Phylum:   Ascomycota
Order:   Helotiales
Family:   Helotiaceae
Occurrence on wood substrate: Saprobic; hardwoods,
especially oak; summer through fall.  
Dimensions:  Cup-shaped to saucer-shaped; 3-8 mm wide;
stalk up to 6 mm long, central to eccentric.   
Sterile outer surface:  Blue-green   
Fertile inner surface: Blue-green, sometimes tinted
yellow.    
Edibility: Unknown
Comments: Twigs, branches, and pieces of wood are
stained green by the mycelium of the fungus. The actual fruit
bodies are less common. Bessette indicates another species,
Chlorociboria aeruginosa, forms nearly identical fruit bodies,
does not stain the wood green, and has larger ascospores.

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Figure 1. Fruit bodies of green stain.

Figure 2. The blue-green, eccentric stalk of Chlorociboria
aeruginascens is clearly seen on the detached specimen
on the left.

Figure 3. These fruit bodies have more of a greenish hue.
Photo © David Work.

Figure 4. These fruit bodies are more cup-shaped than
saucer-shaped. Photo © William Roody.

Figure 5. Note the greenish-colored wood at the broken
end of this branch.

Figure 6. The three pieces of blue-green wood to the right of
the small sycamore leaf were collected during a foray. Stained
pieces of wood are the most commonly collected form of this
fungus.