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Blushing & Blackening Russulas  

[ Basidiomycota > Russulales > Russulaceae > Russula . . . ]

by Michael Kuo

In a large and unmanageable genus of mushrooms that can be ridiculously difficult to identify, the blushing and blackening species of Russula form a subset that can almost be worked with--if you are willing to accept that the species are defined on outdated concepts and that they will undoubtedly change as soon as someone applies contemporary methods to the group.

The blushing and blackening ("rubescent" and "cinerescent," in Mycologese) russulas are not necessarily all closely related, but they do share a feature that allows them to be grouped together for identification purposes: when bruised or sliced open, their surfaces and flesh change color to a reddish color or a gray-black--or to reddish and then gray-black. The color changes are best assessed by rubbing the stem surface (which usually happens in the course of picking and handling the mushroom) and by slicing the mushroom in half. Patience is required, however, since it can take quite a while (up to a half hour or more) for the color changes to develop.

A few of the species (as they are currently defined) are fairly easy to identify; Russula claroflava, for example, is just about the only yellow member of the group. But many of the mushrooms are more difficult to separate, and microscopic analysis is required in quite a few cases; the most frustrating separation in the group requires measuring the thickness of the skin of the cap.

 		 

Russula dissiulans

Russula densifolia

Russula dissimulans


Key to 28 Blushing and/or Blackening Russulas in North America  



1.Cap brown, with conspicuous pinkish cottony scales or patches; possibly known only from the type collection made under northern white cedar in Cheboygan County, Michigan.
Russula decora

1.Cap variously colored (including brown), without pinkish cottony scales; variously distributed.
2


2.Cap evenly yellow; stem and flesh slowly discoloring gray to blackish without a red stage; odor and taste mild; found in conifer and birch bogs in northern and montane North America.

2.Not as above.
3


3.Cap dull orange to coppery orange; stem and flesh discoloring slowly gray without a red stage; found under conifers; pileocystidia present.

3.Not as above.
4


4.Cap orangish brown to brownish orange, with fine yellow powder (especially on the margin) when young; stem becoming orangish yellow with age, bruising deep red on handling; odor reminiscent of maraschino cherries or almonds; taste acrid; KOH on cap surface deep red; associated with oaks; apparently widely distributed east of the Great Plains.

4.Not as above.
5


5.Cap mottled with pinks, purples, and greens (occasionally with browns as well)--or sometimes with one of these shades dominating completely; flesh and stem discoloring slowly pinkish, then gray; odor and taste mild; under conifers in western North America.
Russula occidentalis

5.Not as above.
6


6.Cap red to purple (sometimes mottled with brownish and/or olive shades).
7

6.Cap otherwise colored (white, beige, tan, brown, black).
19


7.Cap purple.
8

7.Cap red.
11


8.Known from California, under Sitka spruce; flesh and stem discoloring gray to black without a red stage; spore print and mature gills yellow; flesh not reacting to phenol; pileocystidia positive in sulphovanillin.
Russula pacifica

8.Known from eastern North America, under various trees; physical features and chemical reactions varying.
9


9.Stem bruising purplish to dull red but not subsequently blackening; cap small (2-4 cm), almost black over the disc or when young; under spruces.
Russula parvula

9.Stem discoloring gray to blackish, without a red stage.
10


10.Associated with conifers; taste mild; stem often flushed with pink (inherent color; not discoloration); spore print dull yellow; spores with isolated warts.
Russula vinosa
= Russula obscura

10.Associated with hardwoods; stem white before discoloring gray with age; spore print white; spores with frequent, fine connectors between warts.


11.Cap brownish red, brick red, cinnamon--or with olive shades, or mottled with these colors.
12

11.Cap fairly evenly some shade of red (perhaps with some whitish to yellowish areas when mature or faded).
14


12.Taste slowly very acrid; odor reminiscent of maraschino cherries gone bad; spores with very low warts (extending only to .3 µ).
Russula burkei

12.Taste mild; odor not distinctive or slightly fishy; spores with low or moderately high warts.
13


13.Spores with very low warts (extending only to .4 µ).
Russula cinerascens

13.Spores with warts extending .6-1 µ.
Russula seperina


14.Cap pale red to pink, sometimes with whitish to yellowish areas; spore print and mature gills yellow; taste acrid; spores with low warts extending only to .5 µ; known from lower elevations in California.
Russula californiensis

14.Not completely as above; physical features varying; taste mild or only slightly acrid; species apparently distributed primarily in eastern North America.
15


15.Stem where bruised turning reddish to red, then blackish.
16

15.Stem where bruised turning gray to blackish without a red stage.
17


16.Cap skin peeling easily over halfway to the center; stem always white before bruising; pileocystidia cylindric to fusiform.

16.Cap skin more adnate than above, peeling only near the margin; stem apex sometimes pink (before bruising); pileocystidia clavate.
Russula rubriceps


17.Associated with hardwoods from the Midwest to northeastern North America; spore print white to creamy.
Russula nigrescentipes

17.Associated with conifers in northern North America; spore print yellow to orangish yellow.
18


18.Cap purplish red to brownish red; spores with isolated warts; pileocystidia absent; encrusted primordial hyphae present.
Russula vinosa

18.Cap red to orangish red; spores with connectors between warts; pileocystidia present; encrusted primordial hyphae absent.
Russula paludosa
sensu Shaffer (1970)


19.Gills pink (inherent color, before discoloring) and well spaced; cap tan to dull brown; stem often bruising pinkish to reddish (without a subsequent change to gray) when very fresh; found in southeastern North America.

19.Not completely as above.
20


20.Growing under coast live oak in California; cap beige to tan; flesh and stem bruising reddish to reddish brown but not subsequently turning blackish; gills close, white before discoloring.
Russula cantharellicola

20.Not as above.
21


21.Flesh and/or stem bruising reddish to red, then changing to grayish or blackish.
22

21.Flesh and/or stem bruising grayish to blackish, almost always without a red stage (occasionally some of these mushrooms will manifest a reddish stage).
25


22.Cap olive to olive gray, olive brown, or brownish (not initially whitish); taste acrid; spores partially to completely reticulate with frequent connectors between warts; growing under conifers.
Russula consobrina

22.Not completely as above.
23


23.Odor heavy and unpleasant, very strong (described as "piggy" and "like . . . a sweating horse"); spore print yellow.
Russula magna

23.Odor not distinctive, slightly fragrant, or slightly unpleasant; spore print white.
24


24.Pileipellis measuring under 150 µ thick under the microscope, not embedded in a gelatinous matrix--with mostly repent, interwoven elements on the surface; cap surface, when rubbed with a fingertip, often with a somewhat waxy, brittle feel; gills usually (but not always) distant or nearly so.
Russula dissimulans
(= "R. nigricans" in N. America)

24.Pileipellis over 150 µ thick and embedded in a gelatinous matrix--often with predominantly upright elements near the surface; cap surface usually softer to the touch than above; gills usually (but not always) close or nearly crowded.


25.Appearing from the Great Plains eastward.
26

25.Appearing from the Rocky Mountains westward.
27


26.Cap developing brown shades; gills crowded; spore ornamentation up to 0.2 µm high (spores often appearing nearly smooth).
Russula sordida

26.Cap not developing brown shades; gills close; spore ornamentation up to 0.5 µm high.


27.Cap sticky when wet; spore ornamentation up to 0.4 µm high.
Russula adusta

27.Cap dry; spore ornamentation usually 0.1 µm high (spores appearing nearly smooth).



References:


Beardslee, H. C. (1918). The russulas of North Carolina. Journal of the Elisha Mitchell Scientific Society 33: 147–197.

Burlingham, G. S. (1915). Russula. North American Flora 9: 201–236.

Burlingham, G. S. (1924). Notes on species of Russula. Mycologia 16: 16–23.

Kibby, G. & Fatto, R. (1990). Keys to the species of Russula in northeastern North America. Somerville, NJ: Kibby-Fatto Enterprises. 70 pp.

Peck, C. H. (1906). Report of the state botanist: New York species of Russula. Bulletin of the New York State Museum 116: 67–117.

Peck, C. H. (1906). New species of fungi. Bulletin of the Torrey Botanical Club 33: 213–221.

Roberts, C. (2007). Russulas of southern Vancouver Island coastal forests. Doctoral dissertation, University of Victoria. Victoria BC, Canada.

Shaffer, R. L. (1962). The subsection Compactae of Russula. Brittonia 14: 254–284.

Shaffer, R. L. (1970). Notes on the subsection Crassotunicatinae and other species of Russula. Lloydia 33: 49–96.

Thiers, H. D. (1997). New species of Russula from California. Mycotaxon 63: 349–358.

Thiers, H. D. (1997). The Agaricales (gilled fungi) of California 9. Russulaceae I. Russula. Eureka, CA: Mad River P. 158 pp.



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Cite this page as:

Kuo, M. (2009, March). North American blushing russulas. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/russulas_rubescent.html


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