Described by mushroom enthusiast
Antonio Carluccio as "not exactly nice to look at", the
cap is at first dome or barrel-shaped, becoming convex and flattened with age with a diameter of up to . The cap center is often depressed. The
cuticle of the cap is green, most profoundly in the center, with patches of the same color dispersed radially around the center in an
areolate pattern. The color of the cuticle is often of variable shade, ranging from gray to
verdigris to grass-green. The extent of the patching of the cuticle is also variable, giving specimens with limited patches a resemblance to other green-capped species of
Russula, such as
R. aeruginea. The green patches of the cap lie on a white to pale green background. The cap, while frequently round, may also exhibit irregular lobes and cracks. The cap cuticle is thin, and can be readily peeled off the surface to a distance of about halfway towards the cap center. The
gills are white to cream colored, and fairly crowded together; they are mostly free from attachment to the
stipe. Gills are interconnected at their bases by veins. The stipe is cylindrical, white, and of variable height, up to tall and wide; it is roughly the same thickness at both the top and the base. The top portion of the stipe may be farinose—covered with a white, mealy powder. It may turn slightly brown with age, or when it is injured or bruised from handling. Like other mushrooms in the
Russulales, the
flesh is brittle, owing to the sphaerocyst cytoarchitecture—cylindrical cells that contrast with the typical fibrous, filamentous
hyphae present in other orders of the
basidiomycota. The
spores of
R. virescens are elliptical or
ellipsoid with warts, translucent (
hyaline), and produce a white, pale or pale yellow
spore print; the spore dimensions are 6–9 by 5–7
μm. A partial reticulum (net-like pattern of ridges) interconnects the warts. The spore-bearing cells, the
basidia, are club-shaped and have dimensions of 24–33 by 6–7.5 μm; they are colorless, and each hold from two to four spores. The pleurocystidia (
cystidia on the gill face) are 40–85 by 6–8 μm and end abruptly in a sharp point.
Similar species Young specimens are pale and can be hard to identify, but the characteristic pattern of older fruit bodies makes them hard to confuse with other species. When collecting
R. virescens for consumption, caution is of vital importance to avoid confusion with the dangerously poisonous
Amanita phalloides (the
death cap), a mushroom that can be most easily identified by its
volva and
ring.
Russula parvovirescens, found in the eastern United States, can be distinguished from
R. virescens by its smaller stature, with caps measuring wide and stipe up to long by thick. Compared to
R. virescens, it tends to be more bluish-green, the patches on its cap are larger, and it has a lined cap margin. Microscopically, the terminal cells in the cap cuticle of
R. parvovirescens are more swollen than those of
R. virescens, which has tapered and elongated terminal cells. Another green-capped
Russula is
R. aeruginea, but this species may be distinguished from
R. virescens by its smaller size and smooth cap. Other green russulas with a smooth cap include
R. heterophylla and
R. cyanoxantha var. peltereaui.
Russula crustosa, like
R. virescens, also has an areolate cap, but the cap becomes sticky (viscid) when moist, and its color is more variable, as it may be reddish, yellowish, or brown. Also, the spore print of
R. crustosa is a darker yellow than
R. virescens.
R. redolens has a cap that is "drab-green to blue-green", but unlike
R. virescens, is smooth.
R. redolens has an unpleasant taste and smells of
parsley. == Habitat and distribution ==