Perenniporia fraxinea

Perenniporia fraxinea (Bull. : Fr.) Ryvarden

[Fomes fraxineus]

Epithet = of ash (Fraxineus). Genus = perennial pored.
Fruits from base of live or dead trees or stumps. Spores white, subglobose or drop-shaped, thick-walled, dextrinoid.
Similar species
The white spores and paler flesh separate it from Ganoderma. Within Perenniporia it is separated by having sessile brackets, pores 4 to 6 per mm, and subglobose spores shorter than 9 micrometers (Gilbertson and Ryvarden 1987). Many of the other species are pored crusts.

Happily, fruitbodies of P. fraxinea have one unique ident. feature which is present at any stage of their development: when cut open, the corky textured flesh is the same creamy fawn colour as the (fresh) exterior. This uniformity of colouration contrasts well with species of the Ganoderma genus and also helps to differentiate P. fraxinea with Rigidoporus ulmarius, another fungus that develops brackets of similar appearance (especially in relation to algal bloom).

J. Forbes-Laird, Monograph on Perenniporia fraxinea.
A "nasty rotter" that should be watched for by city foresters. Perennial pathogen causing white rot in heartwood, at tree base and roots, weakens tree. Typically on Fraxineus (ash) but on many other hardwoods. In British Isles reported from Fagus (beech), Juglans (walnut), Platanus (planetree), Populus (poplar), Robinia (locust), Quercus (oak), Salix (willow), Sambucus (elder), Sophora, Sorbus (rowan), Tilia (linden), and Ulmus (elm).
Recorded for August to November.
Widespread, at least in Europe and eastern North America.
Chicago Region status:
Rare. Newly documented with six collections from 2014 and again in 2015. First time it was found in early August on a club foray in southern Cook County. Rocky worked up the microscopic characters and posted the observation on Mushroom Observer. Five weeks later the second collection was found in northern Cook County by a club member who kindly donated the specimen. Then it was found on four more forays in northern Cook County from September to early November, 2014. The following year, September 2015, it was at a new location in northern Cook County. Then a repeat location in 2016.
Update: there is a photo observation from northern Cook County, February 2020, posted to iNaturalist. Judging from other photo observations on Mushroom Observer and iNaturalist, there seems to be several concepts for the color and appearance of P. fraxinea.
This species, as Fomes fraxineus, was listed in Moffatt (1909) but there were no collections at the Field Museum (F) for this species from anywhere. The six historic collections from 1900 to 1912 were sent to University of California, Berkeley (UC), New York Botanic Garden (NY), and SUNY College of Environmental Science and Forestry Herbarium (SYRF). The UC herbarium labels were printed here, stating: In the Cryptogamic Herbarium, Chicago Natural History Museum. Some of these collections were originally labeled as Fomes fraxineus Bull. (Data from MycoPortal):
  • [UC] W.S. Moffatt 481, 22 Sept. 1900. On standing trunk near ground in woods at Glen Ellyn, Illinois.
  • [UC] E.T. Harper, Oct. 1902. On stumps in River Forest, Illinois.
  • [UC] E.T. Harper & S.A. Harper, Oct. 1903. On Ash stump. River Forest, Illinois.
  • [NY] E.T. Harper, October, sent Nov. 1904. Two seasons on a stump. Riverside, Ill.
  • [SYRF] L. H. Pennington , 06 September 1909, Evanston, Cook County, Illinois.
  • [UC] W.S. Moffatt, Oct. 1912. River Forest, Illinois.
Specimens examined
P. R. Leacock 11749 [A.D. Houghtby MO-172393], 11992, 12119, 12123, 12222, 12320, 12619, 13239.
W.S. Moffatt. The Higher Fungi of the Chicago Region (1909, p. 107).
Fomes fraxineus Bull.
Pileus corky-woody, glabrous, somewhat applanate, whitish, then reddish and brown, at first even, then concentrically sulcate-plicate, pallid within.
Pores minute, short, reddish at first, as well as the margin covered with a white sebaceous down. Odor strong and penetrating.
On stumps. River Forest, Harper; near the ground on a standing trunk, Glen Ellyn. Moffatt. Unfortunately both collectors failed to record the species of tree on which the specimens were found. It is said to grow on Fraxinus americanus.

Taxon Details and Links

  • Perenniporia fraxinea (Bull. : Fr.) Ryvarden, Nova Hedwigia 27: 158 (1976)
  • ≡ Basionym: Boletus fraxineus Bull., Herbier de la France 10: t. 433:2 (1790)
  • ≡ Sanctioned: Polyporus fraxineus (Bull.) Fr., Systema Mycologicum 1: 374 (1821)
  • Fomes fraxineus (Bull. : Fr.) Cooke, Grevillea 14 (69): 21 (1885)
in Europe
Hopefully DNA analysis has provided a stable home for P. fraxinea. Beyond its initial days in Boletus (1790) and Polyporus (1821), this polypore has been transferred (combined) into Trametes (1882), Fomes (1885), Placodes (1886), Ischnoderma (1889), Scindalma (1898), Ungulina (1925), Vanderbylia (1973), Perenniporia (1976), Haploporus (1983), Poria (1984), and Fomitella (1989). Note this is an example where newer combinations are not the accepted placement. The Perenniporia combination was also published by Ryvarden in 1978 (Polyporaceae of N. Europe 2: 307).
FungitobewithTV's channel: Perenniporia fraxinea YouTube Video
BBC News: diseased ash tree falls, kills 3 people - (source)
Julian Forbes-Laird, Monograph on Perenniporia fraxinea [PDF] from Forbes-Laird Arboricultural Consultancy, UK.
Gilbertson, R. L., L. Ryvarden. 1987. North American Polypores. Volume 2: Megasporoporia - Wrightoporia. Fungiflora, Oslo, Norway. 452 pp.
Moffatt, W. S. 1909. The Higher Fungi of the Chicago Region: Part I, The Hymenomycetes. Natural History Survey, Bulletin No. VII, Part I. Chicago Academy of Sciences. 156 pp., 24 plates.
Mushroom Observer
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Cite this page as: Leacock, P.R. (2020 Feb 14). Perenniporia fraxinea - MycoGuide. Retrieved from

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