Xerocomellus small, red-stemmed boletes of Pacific Northwest forests — easy to recognize as a group, hard to tell apart by species
Xerocomellus is a genus of small to medium boletes found across Pacific Northwest forests: a red-streaked or red-dotted stem, bright yellow pores, and a dry, velvety cap that cracks with age in most species, showing pale yellow to pinkish flesh underneath (D. Miller, Danny’s DNA Discoveries; Mushrooms of Cascadia, Siegel & Schwarz). Recognizing the genus is straightforward. Telling the roughly half-dozen Pacific Northwest species apart is not — field guides and mycologists alike describe it as genuinely difficult, resting on small differences in stem color pattern, how fast the flesh and pores stain blue, and which trees a mushroom is growing near (D. Miller, PNW Pictorial Key; Siegel & Schwarz).
Mushrooms of Cascadia rates every Pacific Northwest species it describes as edible.
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What makes something a Xerocomellus
Small to medium size, a dry cap that cracks with age in most species, bright yellow pores, and a stem streaked or dotted with red over a yellow background. None has the thick, bulbous, red-netted stem and red pores of the toxic red-pored boletes (Rubroboletus).
Misapplied European Names
Two of the most common Pacific Northwest species were long identified under European names that don’t actually occur here. Older books, and even some current ones, still use the wrong name.
- Xerocomellus chrysenteron is a European species. The common Pacific Northwest cracked-cap bolete long called by this name was only formally described as its own species, Xerocomellus diffractus, in 2015 (Siegel & Schwarz; D. Miller). If you see “chrysenteron” used for a Pacific Northwest bolete, it usually means X. diffractus.
- Xerocomellus (Boletus) truncatus is an eastern North American species. The similar-looking Pacific Northwest bolete with an extensively red, dotted stem and truncate (squared-off) spores is Xerocomellus mendocinensis (Siegel & Schwarz; MycoMatch; D. Miller).
Pacific Northwest Species
Seven species have been documented in Cascadia with enough detail to describe here. Field separation depends on cap cracking pattern, how far up the stem the red coloring reaches, staining speed, and habitat — often several of these together, not any single feature.
Zeller’s Bolete (Xerocomellus zelleri)
A dark, nearly black cap — sometimes olive-brown or gray — with a narrow, paler whitish-tan band running around the extreme rim at every stage. Pores are pale creamy yellow and rarely stain blue. The stem is slender and mostly red. It grows scattered on and near rotting stumps, logs and mossy woody debris beneath conifers, mainly in mature and old-growth coastal forests such as the Olympic Peninsula and the Cascade foothills (Siegel & Schwarz). It can be locally common in the right old-growth habitat but is quite rare across the region as a whole. The far more common look-alike below, X. atropurpureus, was lumped under this name before being split out in 2020; the pale cap-margin band and slender build point to true zelleri (Siegel & Schwarz; Frank et al.). Edible.
Deep Purple Bolete (Xerocomellus atropurpureus)
A dark blackish-purple to deep wine-red cap, usually bumpy-wrinkled rather than smooth, without the pale marginal band that zelleri almost always shows. Pores are dull yellow and only rarely bruise blue. The stem is stockier than zelleri’s, yellow with red streaks or punctations. It grows from duff, soil or well-decayed wood under both conifers and hardwoods and is very common and widespread across a wide range of habitats (Siegel & Schwarz), fruiting mainly in fall and winter with occasional spring appearances. Edible and good (Siegel & Schwarz).
Cracked-cap Bolete (Xerocomellus diffractus)
The species usually meant by the misapplied name “chrysenteron” (see above). An olive to leather-brown or tan, velvety cap that cracks extensively with age, showing pale yellow flesh that turns pinkish in the cracks. Pores are pale yellow and only slowly to moderately turn a dull bluish-gray. The yellow stem carries fine red punctations concentrated toward the base, often sparse or absent near the top. Common and often abundant across a wide variety of trees and habitats, including urban areas under Douglas-fir (Siegel & Schwarz); fruiting from late summer at higher elevations through fall and early winter at lower elevations. Edible with good flavor when young, though older caps go soft and mushy.
Xerocomellus mendocinensis (formerly misapplied as “truncatus”)
No widely used common name. Dark olive-brown to medium brown cap, cracking mainly near the margin (occasionally more extensively). The stem is heavily dotted with red over a yellow background, often nearly solid red near the top. Both the pores and flesh stain dark blue almost instantly — noticeably faster than most other Xerocomellus in the region (Siegel & Schwarz). Found beneath conifers as well as hardwoods; it ranges across western Cascadia yet is common only toward the southern end of that range, fruiting in fall. Edible but soft-textured (Siegel & Schwarz).
Xerocomellus amylosporus
No widely used common name. A dark vinaceous-brown to olive-brown cap that cracks irregularly, revealing pale to pinkish flesh. The stem is dotted with red over yellow when young but browns with age — the main way to tell it from the similar X. mendocinensis, whose stem stays red. Pores stain inky blue moderately quickly. Occasional, found mostly in older coastal spruce stands and old-growth forest of the Cascade foothills, growing with conifers (Siegel & Schwarz); fruits in fall. Edible.
Xerocomellus rainisiae
No widely used common name. A dark olive to blackish-brown cap with an unusually thick velvety-tomentose surface that cracks less than the other species here. The stem is mostly smooth or lightly punctate rather than heavily red-dotted, and stains an unusually intense dark blue-green to greenish-black when handled — a distinctive color among the region’s Xerocomellus (Siegel & Schwarz). Uncommon to rare, mostly from old-growth conifer forest; along the coast it appears from autumn’s later half through the start of winter, while at higher elevations it instead shows up in summer and fall. Edible.
Xerocomellus salicicola
No widely used common name. A dull red, tan or brown cap that cracks extensively, with pinkish-yellow flesh showing through. The reddish stem is coarsely net-patterned near the top. Pores and flesh both stain dark blue fairly quickly. The clearest field clue is the tree it’s growing under: it’s largely restricted to willow and cottonwood, sometimes birch in landscaped settings, usually in wet or hard-packed soil (Siegel & Schwarz). Typically fruits in fall but can fruit into spring and summer in irrigated areas. Edible.
Truffle-like Relatives, and an Oak Bolete
Two Xerocomellus species don’t look like boletes at all. X. behrii and X. mcmurphyi are small, rounded, truffle-like fungi that fruit underground, mostly with oaks. Both were described from California and have also been found in Oregon, including under Oregon white oak (D. Miller; M. E. Smith). X. behrii is bright yellow to off-white, browning where handled, with a spinach-like odor; X. mcmurphyi is pale yellow turning gray, olive and brown, and smells of garlic butter (M. E. Smith). A third truffle-like bolete from California, ‘Gastroboletus’ xerocomoides, shares its ITS DNA with X. amylosporus (D. Miller).
Separately, X. dryophilus is an ordinary red-capped bolete of California oak woodlands. It has been rumored from Oregon but not yet confirmed there by DNA (D. Miller).
Close Relatives That Get Confused With Xerocomellus
Two other small genera in the same family share the red-stem, yellow-pore look and are commonly mistaken for Xerocomellus (D. Miller; D. Miller, PNW Pictorial Key). One field clue helps sort them: Hortiboletus has orange granules in the flesh at the base of the stem that Xerocomellus lacks.
- Hortiboletus coccyginus: bright pinkish-red, velvety cap over an orange-brown stem that is not red, with pores that usually don’t stain blue. Found with cottonwoods and some non-native trees; rare in the Pacific Northwest (Bessette).
- “Hortiboletus rubellus”: red velvety cap, a stem that is yellow at the top and reddish below, with weak blue staining. The name is applied loosely here — Pacific Northwest material is not the same as the European species and needs a new name of its own (D. Miller, pers. comm., via MycoMatch).
- Hortiboletus bubalinus (“Ascot Hat”): yellow-brown to pale brown cap, often flushed pink, over a stem striped dark yellow-brown to brown. At least two distinct entities are going by this name in the region — one reddish and fat-stemmed under willow near Seattle, the other browner and thinner-stemmed under birch — and neither is fully sorted out taxonomically yet (D. Miller).
- Pulchroboletus (likely home of “Boletus” smithii): Smith’s bolete has red confined to the top of the stem rather than the base, and a cap that reddens where rubbed. It hasn’t formally been moved into Pulchroboletus yet, but DNA data point that way (D. Miller). Its cap fades through yellow to gray with age, when it can resemble a faded Xerocomellus — see the Smith’s Bolete guide.
Season
Across the genus, Pacific Northwest observations run from spring through winter but are heavily concentrated in fall, peaking in October and staying strong into November before tapering off in December:
Based on 9,574 iNaturalist observations of the genus Xerocomellus from Oregon and Washington
A few species run slightly earlier or later than the genus average: X. diffractus starts fruiting in late summer at higher elevations, X. rainisiae can extend into winter along the coast, and X. salicicola occasionally fruits in spring or summer in irrigated settings (Siegel & Schwarz). Species-level counts for X. zelleri specifically are not reliable here: it was long confused with the much more common X. atropurpureus before the two were separated as distinct species in 2020, so older and unreviewed observations under “zelleri” likely include many misidentified atropurpureus (D. Miller).
Edibility
Every Pacific Northwest Xerocomellus species that Mushrooms of Cascadia covers is rated edible, and none is known to be toxic. Quality varies by species: X. atropurpureus is rated edible and good, while X. diffractus is good when young but goes soft and mushy with age, and X. mendocinensis is edible but soft-textured throughout (Siegel & Schwarz).
Try the Bolete Finder
Identify Pacific Northwest boletes with our step-by-step guide. Answer questions about cap color, pore characteristics, and staining reactions to narrow down your find.
Sources: Mushrooms of Cascadia (Siegel & Schwarz, 2024); MycoMatch (© Ian Gibson), a compilation of published descriptions through which most other field-guide authors named here are quoted; Danny’s DNA Discoveries and the PNW Pictorial Key (© Danny Miller); iNaturalist observations.