Two-Colored Bolete – Boletus bicolor


Common Name: Two-Colored Bolete, Red and Yellow Bolete – The red of the pileus or cap is sharply contrasted by the yellow spore-bearing pore surface on its underside. Bolete is the general name for any mushroom-shaped (i. e. having a cap and a stem) fungus with pores instead of gills. It is also, in this case, a shortened form of the generic name Boletus.

Scientific Name: Boletus bicolor – The genus Boletus is one of two words for ‘mushroom’ in Latin (the other is fungus, from which the Kingdom Fungi is derived). The likely reason for the duality of mushroom names is that Boletus is from the Greek word bolites derived from bolos which means ‘clod.’ Though likely apocryphal, this presumably refers to the appearance of mushrooms as clods (of dirt) in the forest. The species name is ‘two-color.’

The Two-Colored red and yellow bolete is variable to the extent of masquerade, a characteristic that it shares with the other pored fungi that are broadly called boletes. While it is universally described with a reddish cap and yellowish pores, all of its other attributes are subject to nebulous uncertainty. While some variance is related to the maturity of the individual mushroom, some is due to lack of specificity in form and coloration. The cap can be rose-red to pinkish, the pore surface under the cap can be bright yellow to pale olive-yellow and the stem or stipe can be equal in diameter along its length or club-shaped, dark red or rosy red at the bottom and yellow at the top or, if none of the above, almost all yellow. It is therefore only accurate to assert that if you find a mushroom with a red cap and a yellow pore surface, it might be Boletus bicolor. Then again, it might be something else altogether.

The boletes are notorious for their inconsistent field appearance, a fact that is mirrored in their torturous taxonomy. As a group, they are set apart from other mushroom-shaped fungi by the porosity of the ventral side of the cap; whereas most mushrooms have spore-bearing gills, boletes have pores. Each pore is an opening that marks the end of a tube that extends vertically upward; the walls of each tube support the hymenium, the name for the spore producing structure of the fungus. In keeping with the exasperating inconsistency of the boletes, there is (at least one) bolete with gills with the oxymoronic name ‘gilled bolete’ (Phylloporus rhodoxanthus). While there have been a number of contradictory attempts to work out the taxonomic details of the boletes, it has been generally accepted that there is a bolete family (Boletaceae) with as many as 18 genera. The taxonomy in some texts is elevated to the order Boletales with several families, only one of which is Boletaceae. However, given the diversity of the bolete clan, it is best to concentrate on four most widely represented genera: Boletus is the largest genus with centrally located stem and the characteristic sponge-like texture on the underside of the cap; Suillus (Latin for swine) is characterized by mushrooms with glutinous or sticky caps; Leccinum boletes have mottled stems that are sometimes called scabber-stalks; and lastly the Tylopilus species have pink spores in lieu of the normal boletaceous olive-brown spores with, for the most part, a very bitter taste.

However, all of this is moot in light of advances in DNA phylogenetic analysis. In a recent paper entitled “Molecular Phylogeny and Biodiversity of the Boletes,” Vilgalys, James and Drehmel from the Duke School of Biology evaluated the diversity of boletes by counting species and conducting phylogenic analyses. They concluded that there is “a deep divergence between suilloid (i.e. of the genus Suillus) fungi and Boletus and allies and a distinct Leccinum clade.” In other words, only the relatively few pore-bearing boletes of the genera Suillus and Leccinum are monophyletic while the other so-called genera are polyphyletic, a farrago of tangled genetic interbreeding. Arguably the new order of fungi according to phylogenesis is in statu nascendi; over the course of the next several decades, the true taxonomy of the boletes may be revealed. According to Michael Kuo of, “it is clear that big taxonomic changes are coming soon to a Boletus in your viewing area.” Until then, the two-colored bolete could be one mushroom or it could be many.

The poisonous red-mouth bolete

Boletes are for the most part edible; one of the world’s most renowned edibles, second only perhaps to the morel, is Boletus edulis, the King Bolete. No boletes are known to be deadly; however a few that can make you very sick. In Mr. Bloomfield’s Orchard, Nicholas Money opines that Boletus satanus, understandably known as Satan’s Bolete “can make people shit themselves senseless.” Caution in bolete ingestion is thus in order. This is problematic since there is a lack of clear and reliable descriptions of the pore-surfaced mushrooms; they are simply too variable. The paucity of absolutes in field bolete identification conflated with the overarching desire of mushroom hunters to harvest edible species has resulted in the establishment of a workable standard for bolete edibility based on empirical evidence. It is considered safe to eat any bolete that: (1) Does not have a red pore surface; (2) Does not stain blue, and (3) Does not taste bitter. The red pore surface caveat prevents the unfortunate ingestion of the Red-mouth Bolete (B. subvelutipes) which would result in a similar (though perhaps less graphic) outcome to the aforementioned Satan’s bolete. The bluing caveat prevents eating the Boletus sensibilis, which is noted for turning to blue with great celerity, and, according to Bill Roody in Mushrooms of West Virginia and the Central Appalachians, having “a sweet odor of fenugreek or curry.” It is reputed to be poisonous, but this is conjectural though perhaps anecdotal. The preclusion of bitter boletes, which largely rules out the genus Tylopilus (one of which is actually called bitter bolete), is mostly a matter of prandial concern. If you add a bitter bolete to an otherwise salubrious stew, the result will be a bitter experience. Bitterness can readily be discerned by placing a small piece of the mushroom on the tongue; the taste buds do the rest.

The blue stain is indicative of caution when eating boletes

The Two-Colored bolete is considered edible; however it violates the “safe-to-eat” bolete rule. The problem with B. bicolor and edibility is that it stains blue; its doppelganger is the toxic blue-staining B. sensibilis. The bluing of boletes has long been a matter of some scientific interest. The French biochemist Gabriel Bertrand offered the explanation in a 1901 article “On the Blue Color Taken by Certain Mushrooms of the Genus Boletus” that the blue color “necessitates the cooperation of six different factors: oxygen and boletol; laccase; manganese; water; and, finally, an alkaline metal, magnesian or alkaline earthy.” This is the basis for the version that has made its way into most books that discuss the subject of fungal bluing, the color purportedly the result of the oxidation when the mushroom flesh is exposed, much like the staining of an apple. The proffered chemistry is that the boletol and laccase are normally separate, becoming comingled by the incision of the mushroom or by its having been bruised – the compounded chemicals then turning blue by the oxygenation of the air. A 2010 article in the magazine Fungi entitled “Bluing Components and Other Pigments of Boletes” by S. Nelsen from the University of Wisconsin Chemistry Department provides the chemistry of the reaction according to modern and detailed analytical laboratory techniques. About the only thing that Bertrand got right was that it is complicated. A compound called variegatic acid is oxidized by oxidase enzymes to produce another compound called quinone methide, which is blue; if it is oxidized in air, you get variegatorubin, which is red. This complex chromatic chemistry is probably the root cause for the high variability of the palette with which nature paints the bolete.

Most field guides list Boletus bicolor as edible, though there are varying degrees of certitude. At one extreme is McIlvaine’s One Thousand American Fungi which offers the superlative “fine eating, one of the very best,” while Lincoff’s Audubon Field Guide to North American Mushrooms is almost as effusive with the terse “choice edible.” Roody’s Mushrooms of West Virginia advises the more nuanced “edible with caution,” noting further that “some individuals have reported having gastrointestinal disturbance from eating Boletus bicolor or a closely related species.” (Jon Ellifritz, the former president of the Mycological Association of Washington DC asserts that one of the ‘some individuals’ includes Roody, who became nauseous after eating a bicolor bolete and no longer eats them). The most detailed accounting is provided by North American Mushrooms, a Falcon Field Guide. It lists three other species that turn blue that might be confused with the bicolor bolete (B. miniato-olivaceus, B. fraternus and B. pulverulentus) with potential deleterious side effects and concludes with “We strongly recommend consulting an expert if in doubt about the identity of a species in this group.” The problem with this caveat is the bolete experts are few and far between, if they even exist.

Slow blue staining of B. bicolor

For those inclined to a bold approach to mychophagy, (akin to those who eat fugu – the Japanese pufferfish whose lethal parts must be excised) eating red and yellow boletes may provide a level of anxious excitement to an otherwise dull meal – to say nothing of the gastrointestinal deluge that might result. Since B. bicolor does not have a red pore surface and does not taste bitter, it is only the bluing that stands in the way of a reliable identification (laying aside the inherent variability of the species). This can be addressed by determining the rate and degree to which the flesh of the mushroom stains blue. The poisonous B. sensibilis stains blue rapidly, the edible B. bicolor less so. A reasonable field test is to press the bottom of the pore surface with one’s thumb. If it takes a few seconds to turn blue, it is likely that it is the edible B. bicolor and is safe to eat. As in all decisions about mushroom edibility, however, caveat emptor.