# Boletus barrowsii
**Boletus barrowsii** Thiers & A.H. Sm., commonly called Barrow's bolete or the white king bolete, is a whitish, probably edible bolete fungus of the family [Boletaceae](https://www.edgepedia.org/boletaceae) found in western North America, closely related to the porcini *Boletus edulis*. It was described in 1976 in *Mycotaxon* (volume 3, page 262) by Harry D. Thiers and Alexander H. Smith, and the name is currently accepted.[1](https://sweetgum.nybg.org/science/projects/boletineae/taxon-checklist/taxon-details?irn=37689) The species belongs to the *Boletus edulis* group, a set of robust, reticulate-stemmed boletes whose pore surfaces do not bruise blue.[2](https://www.mushroomexpert.com/boletus_barrowsii.html)
| Key fact | Detail |
|---|---|
| Scientific name | *Boletus barrowsii* Thiers & A.H. Sm., 1976; primary citation *Mycotaxon* 3: 262; isotype specimen H. D. Thiers HDT27816[1](https://sweetgum.nybg.org/science/projects/boletineae/taxon-checklist/taxon-details?irn=37689) |
| Common names | Barrow's bolete, white king bolete[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html) • [4](https://practicalselfreliance.com/bolete-mushrooms/) |
| Cap | 5–16 cm, convex becoming broadly convex or almost flat, dry, dull, bald, whitish becoming pale brownish with age[2](https://www.mushroomexpert.com/boletus_barrowsii.html) |
| Stem | 5–15 cm long, 2–5 cm thick, club-shaped when young, whitish, finely reticulate over the upper portion or nearly overall[2](https://www.mushroomexpert.com/boletus_barrowsii.html) |
| Spores | 12–17 × 4.5–6 µm, fusiform, smooth, ochraceous in KOH; spore print olive brown[2](https://www.mushroomexpert.com/boletus_barrowsii.html) |
| Hosts | Mycorrhizal with ponderosa pine and occasionally spruces in the Southwest and Colorado, and with coast live oak on the West Coast[2](https://www.mushroomexpert.com/boletus_barrowsii.html) |
| Range | Southwestern United States and Colorado, the West Coast, ranging as far north as British Columbia[2](https://www.mushroomexpert.com/boletus_barrowsii.html) |
## Taxonomy and naming
The species was once thought to be only a variety of *Boletus edulis* and is now considered a distinct species.[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html) It was named for Charles "Chuck" Barrows, a self-taught amateur mycologist of [Santa Fe, New Mexico](https://www.edgepedia.org/santa-fe-new-mexico), who studied the region's mushrooms for decades and noticed the unusually pale coloration and somewhat different habitat of these boletes compared with classic *B. edulis*. He sent dried specimens with careful descriptions of the fresh mushrooms to Alexander H. Smith and Harry D. Thiers at the University of Michigan, who agreed the fungus was a new and distinctive species and named it after him.[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html) Barrows, who died in 1989 at age 85, also founded the New Mexico Mycological Society, and his name is attached to several other species he discovered, including *Lactarius barrowsii* and *Amanita barrowsii*.[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html)
In the NCBI taxonomy database the species sits in [Basidiomycota](https://www.edgepedia.org/basidiomycota), Boletales, Boletaceae, genus *Boletus* (taxonomy ID 495273).[5](https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=495273)
## Description
The fruitbody is a large, whitish member of the *B. edulis* group with a robust, finely reticulate stem and a non-bruising pore surface.[2](https://www.mushroomexpert.com/boletus_barrowsii.html) The cap measures 5–16 cm across and is whitish, becoming pale brownish with age. The pore surface is whitish and appears "stuffed" (covered with a white coating) when young, becoming yellow and eventually olive yellow, with 1–2 pores per millimeter at maturity and tubes up to 2 cm deep; it does not bruise. The flesh is white and does not stain on exposure, and the odor and taste are pleasant but not distinctive.[2](https://www.mushroomexpert.com/boletus_barrowsii.html)
A key microscopic distinction from *B. edulis* is the cap surface: *B. barrowsii* lacks the clearly differentiated, often viscid cap cuticle of that species, with the pileipellis not clearly separated from the flesh of the cap.[2](https://www.mushroomexpert.com/boletus_barrowsii.html) • [6](https://www.svims.ca/council/Bolete.htm) Spores are fusiform and smooth, 12–17 × 4.5–6 µm, ochraceous in KOH, and hymenial cystidia measure 30–40 × 10–15 µm.[2](https://www.mushroomexpert.com/boletus_barrowsii.html) A Pacific Northwest key gives a slightly narrower spore range of 13–15 × 4–5 µm and notes a cap of 9–10 cm that can become brown when bruised.[6](https://www.svims.ca/council/Bolete.htm)
## Ecology and distribution
*Boletus barrowsii* is ectomycorrhizal, forming nutrient-exchange partnerships with tree roots. In the Southwest and in Colorado it associates with ponderosa pine and occasionally spruces, fruiting in summer and fall during the monsoon season; on the West Coast it associates with coast live oak and fruits in fall and winter. It grows alone, scattered, or gregariously, and ranges as far north as [British Columbia](https://www.edgepedia.org/british-columbia).[2](https://www.mushroomexpert.com/boletus_barrowsii.html) A Pacific Northwest key records the habitat as under ponderosa pine, firs (*Abies*), spruce, and live oak, sometimes in deserts, with vouchered occurrences in Idaho, California, Washington, and British Columbia.[6](https://www.svims.ca/council/Bolete.htm) Tom Volk, a mycologist at the University of Wisconsin–La Crosse, describes it as preferring edge habitats with ponderosa pine rather than the deeper woods favored by *B. edulis*, and reports that it is sweeter and larger than its cousin.[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html) Insects also attack the fruitbodies heavily, so unblemished specimens can be hard to find.[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html)
In British Columbia the species is tracked by the provincial Conservation Data Centre with a global rank of GNR (globally unranked/not yet assessed) and a provincial status of S2? as of March 2021, placing it on the provincial Red list of species of conservation concern.[7](https://a100.gov.bc.ca/pub/eswp/speciesSummary.do;jsessionid=3EEF6FD4728278554DD6E43B3BFDAAA2?id=347997)
## Relation to *Boletus edulis* and edibility
The species is a paler close relative of *Boletus edulis* with a more restricted distribution.[3](https://botit.botany.wisc.edu/toms_fungi/aug2004.html) Field guides treat it as a white king bolete found in western North America, including Colorado and the southwestern Sky Islands.[4](https://practicalselfreliance.com/bolete-mushrooms/) The Pacific Northwest key lists its edibility as unknown but probably edible, since it is closely related to *B. edulis*.[6](https://www.svims.ca/council/Bolete.htm) Because several whitish and brownish members of the *B. edulis* group overlap in range and appearance, identification in the field rests on the combination of the pale, dry cap, the non-bruising white-to-yellow pore surface, the finely reticulate stem, and the absence of a distinct cap cuticle.[2](https://www.mushroomexpert.com/boletus_barrowsii.html)
## References
1. [Taxon Details: Boletus barrowsii Thiers & A.H.Sm., Boletineae project, New York Botanical Garden](https://sweetgum.nybg.org/science/projects/boletineae/taxon-checklist/taxon-details?irn=37689)
2. [Kuo, M. (2022). Boletus barrowsii, MushroomExpert.Com](https://www.mushroomexpert.com/boletus_barrowsii.html)
3. [Volk, T. J. (2004). Boletus barrowsii, Chuck Barrows' bolete, Tom Volk's Fungus of the Month](https://botit.botany.wisc.edu/toms_fungi/aug2004.html)
4. [Foraging King Boletes (and Other Bolete Mushrooms), Practical Self Reliance](https://practicalselfreliance.com/bolete-mushrooms/)
5. [NCBI Taxonomy Browser: Boletus barrowsii, Taxonomy ID 495273](https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=495273)
6. [Trial Field Key to the Boletes in the Pacific Northwest, Pacific Northwest Key Council](https://www.svims.ca/council/Bolete.htm)
7. [B.C. Conservation Data Centre, Species Summary: Boletus barrowsii](https://a100.gov.bc.ca/pub/eswp/speciesSummary.do;jsessionid=3EEF6FD4728278554DD6E43B3BFDAAA2?id=347997)
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*Topic: Encyclopedia › Life and health › Microorganisms and fungi › Fungi and mycology › Basidiomycete taxa › Agaricomycetes › Boletales › Boletus sensu lato › Boletus: other species and species lists*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license