As of November, 2015 attempts to quantify the North American Red- and Orange-Capped Leccinums can only be described as a wet, hot mess. You can find an excellent set of discussions by Dr. Michael Kuo at his MushroomExpert.com site, including one on the North American mushroom formerly known as L. aurantiacum, another on the North American Leccinum problem in general, and this giant Leccinum poster to show the issues visually.
How bad can it be? Consider this:
- The primary distinguishing feature for red-capped leccinums is what tree they are growing with, combined with the color of the scabers and the staining characteristic for the flesh. Those are all helpful indicators.
- The primary problem with distinguishing the red-capped leccinums is the fact that the various species are not polite enough to restrict themselves to a particular type of tree even if they have a preference, and will vary both their scaber color and their staining characteristics according to age, environmental effects, and other normal variations within the species.
- Thus the indicators cannot be used as actual proof. They just help you establish the odds.
Frustrated yet? Just wait! It gets even more confusing.
First we need to start with a bit of history. In Europe there are several well-defined species: L. aurantiacum, which has red-brown scabers & grows under hardwoods, L. vulpinum, which has black scabers & grows under conifers, L. piceinum, a duller-capped species that grows under spruce, etc. All are excellent edibles that were much desired by the European settlers in North America.
Simply using the European names would have been bad enough, but relatively easy to solve by assigning new ones depending on whether genetic tests proved that any given species could or couldn’t span both sides of the Atlantic. Such was not to be, however.
The settlers did not just import the European names. Instead they used use the single name “aurantiacum” to describe all of the red-capped North American red-caps without regard to what tree they grew with, how they stained, or how the scaber colors might vary. And, indeed, most of the so called “aurantiacum” found in North America was actually growing with some kind of conifer. In other words the only thing we can guarantee is that the mushroom known as L aurantiacum across the Northeast is not the actual aurantiacum from Europe. It may actually be L. vulpinum but even that isn’t clear because the Leccinums have lagged behind badly when it comes to DNA tests.
The bottom line is this: The people who know these things are morally certain that (a) the North American red-capped Leccinums include a spectrum of similar-looking species, (b) pretty much all the names in the field guides will someday have to be changed as those species get better defined, and (c) there are probably some European species mixed in just to keep us all on our toes. Until that gets settled out my solution will be to have the Bolete Filter use the old, known-to-be-improper names as “placeholders” for whatever is going to happen in the future. Here are the basic dividing lines:
GENERAL, CROSS-REGION NAMES
| Name | Placeholder or Species | Associates | Cap Shade | Scaber Color | Flesh Staining |
| cf. Aurantiacum | Placeholder | Poplar & oak, but also birch & hardwoods in general | Bright orange or red | Red-brown | First reddish, then darkening to purple-gray or black |
| Insigne | Placeholder | Birch & aspen | Rusty-orange to cinnamon-brown | Brown | Purple-gray with no red phase |
| cf. Piceinum | Placeholder | Spruce | Dull Orange | Start white, age through orange to brown/black | First reddish, then darkening to purple-gray or black |
| cf. Vulpinum | Placeholder | Pine & aspen, or other conifers | Bright orange or red | Black | First reddish, then darkening to purple-gray or black |
EASTERN NAMES
| Name | Placeholder or Species | Associates | Cap Shade | Scaber Color | Flesh Staining |
| Arenicola | Species | Sandy Atlantic beaches with beach grass & the like | Orange to yellow-orange | White-buff aging to tan or yellow-brown | First reddish, then darkening to purple-gray or black |
| Areolatum | Species | Birch & aspen | Pale pinkish-cinnamon | Black | First lilac, then darkening to purple-gray or black |
| Discolor | Species | Pine & aspen | Orange (from yellow- to brown-) | Brown-Black | First pinkish, then darkening to purple-gray or black |
| Potteri | Species | Large-toothed aspen & oak | Tawny- to brick-orange, often with white patches from a baby veil | White-buff aging through yellow-brown to brown-black | First reddish, then darkening to purple-gray or black |
| Pseudoinsigne | Species | Birch & aspen | Yellow to red-orange, sometimes viscid | White aging through orange-brown to black | Youngsters stain reddish cinnamon & resolve to bluish-brown or gray.
Mature specimens stain violet-gray. |
| Subtestaceum | Species | Birch & aspen | Rusty- to orange-red, sometimes liver-colored | Black | Purple-gray with no red phase |
| cf. Versipelle | Species | Birch, but also beech & oak | Orange, aging to pinkish tan | Black | First reddish, then darkening to purple-gray or black |
WEST COAST NAMES
| Name | Placeholder or Species | Associates | Cap Shade | Scaber Color | Flesh Staining |
| Aeneum | Species | Manzanita, bearberry, & their relatives | Red-, orange, or copper-orange | Fine, starting white & soon aging to brown-black | Purplish gray without a red phase |
| Arctostaphylos | Species | Kinnikinnick at higher elevations or bearberry in the tundra | Brick orange, sometimes tacky | Whitish, aging through orange-brown to brown. | Pale bluish gray without a red phase |
| Armeniacum | Species | Madrone | Apricot-orange, viscid, often pitted | White | Pinkish, if at all |
| Barrowsii | Species | Conifers in New Mexico | Pale rose-pink | White, aging/drying to dark gray | Unknown |
| Fallax | Species | Conifers | Rusty-red to dark red-brown | White-buff, bruising reddish-brown | DNS |
| Fibrillosum | Species | Conifers | Reddish brown | Black | First reddish, then darkening to purple-gray or black |
| Largentii | Species | Toyon, madrone, or manzanita | Orange-red to red-brown, sometimes tacky | Brown-black, sometimes forming netting | First pink, then darkening to purple-gray or black |
| Manzanitae | Species | Manzanita or madrone | Red or red-brown, viscid | White, darkening to gray-black | Purplish gray without a red phase |
| Ponderosum | Species | Decaying pines | Orange to brick-red | Purple-black, bruising blue | DNS |
| Subalpinum | Species | High altitude conifers | Red-brown to rusty-red | White-buff, bruising reddish brown | DNS or purplish gray without a red phase |