Phaeolus schweinitzii (Fr.) Pat. - Dyer's Mazegill

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Polyporales - Family: Fomitopsidaceae

Phaeolus schweinitzii, Dyer's Mazegill - young fruitbodies

This large bracket fungus appears at the roots of conifers, mainly pine and spruce trees, sometimes in two or three overlapping tiers. It is an annual bracket and can be either round or fan shaped with a distinctive yellow margin blending, as the fruitbody matures, to a browner central region.

Phaeolus schweinitzii, young fruitbody, France


Fairly common in Britain and Ireland, this polypore occurs throughout mainland Europe and in many other parts of the world including North America.

Phaeolus schweinitzii, Dyer's Mazegill - a mature fruitbody

Taxonomic history

The basionym of this species was established in 1821 by Swedish mycologist Elias Magnus Fries, who gave it the binomial scientific name Polyporus schweinitzii. In 1900 the French mycologist Narcisse Theophile Patouillard (1854 - 1926) transferred this species to the genus Phaeolus, thus establishing its currently-accepted scientific name as Phaeolus schweinitzii.

Synonyms of Phaeolus schweinitzii include Polyporus schumacheri (Fr.) Pat., Hydnum spadiceum Pers., Polyporus schweinitzii Fr.,Polyporus herbergii Rostk., Polyporus spongia Fr.,Daedalea suberosa Massee, and Phaeolus spadiceus (Pers.) Rauschert.

Phaeolus schweinitzii is the type species of the genus Phaeolus, in which this is the only species known to occur in Britain.

Phaeolus schweinitzii, Dyer's Mazegill - an old fruitbody

Some authorities place the Phaeolus genus within the family Polyporacea, but here we follow the Kew/British Mycological Society taxonomic system which places Phaeolus and hence this species within the family Fomitopsidaceae.

Phaeolus schweinitzii, Dyer's Mazegill - a very young fruitbody


The generic name Phaeolus comes from the prefix Phae- meaning dusky or obscure, and olus which modifies the meaning to 'somewhat' - so fungi in this genus are described as 'somewhat dusky' or perhaps darkish. The specific epithet schweinitzii honours American botanist-mycologist Lewis David von Schweinitz (1780-1834), considered by some to be the founding father of North American mycological science.

The specimen shown above was photographed in southern Portugal in January, when the fruitbody was dry and very light in weight. Two months later it was still intact but had turned black.

The common name Dyer's Mazegill comes from its use in dyeing yarn various shades of yellow, orange and brown, depending on the age of the fruitbody and the type of metal used as a mordant to bind the dye molecules to the fibres of the fabric.

Identification guide

Close-up of margin of Phaeolus schweinitzii - Dyer's Mazegill


This fairly common polypore has a yellow felty margin and a brownish central region, usually concentrically zoned; the glistening (fertile) pore surface is sometimes hidden from view because of the low-growing habit of these fruitbodies. Typically 15 to 25cm in diameter and 2 to 5cm thick. When there is a stem it is brown, and the attachment is either central or eccentric; stems are short (up to 6cm in length) and stout (typically 3 to 5cm in diameter), tapering towards the base.

Initially the fruitbodies are soft and spongy, eventually becoming dry and hard. Often compound (several fused together), they tend to grow around and so enclose twigs, pine needles, grass and other objects as the caps expand.

Pore surface of Phaeolus schweinitzii

Tubes and Pores

The tube layer can be up to 1.5cm thick, with pores spaced at 1 to 3 per mm on a greenish-yellow background that gradually turns reddish brown with age. Occasionally adjacent tubes may fuse together to produce a few large irregular pores.



Ellipsoidal to ovoid, smooth, 5-7 x 3.5-5µm; inamyloid.

Spore print

Very pale yellow.


No noticeable odour; slightly bitter taste.

Habitat & Ecological role

Parasitic on the roots of coniferous trees, particularly pines and spruces but also occasionally larches. This polypore can kill its host, whereupon it turns saprobic and feeds on the dead roots and stumps once the tree topples or is felled. This fungal infection, sometimes referred to as Schweinitzii Butt Rot, can cause significant economic loss to forestry enterprises.


Throughout summer and autumn, but in dry climates old fruitbodies sometimes persist through to the start of the New Year.

Similar species

Laetiporus sulphureus is all-over yellow-orange and most often grows above the root system of hardwood trees and occasionally on Yews.

Phaeolus schweinitzii, Dyer's Mazegill, under pines in the New Forest, Hampshire, England

Culinary Notes

Dyer's Mazegill Phaeolus schweinitzii does not appear to be crying out 'Eat me; I'm delicious', and in fact it is generally regarded as inedible because it is such a hairy squidgy mess when young and a tough, corky fungus when fully mature. It is also possible that this polypore contains toxins, and so we strongly advise against attempting to eat even the young fruitbodies.

Reference Sources

Fascinated by Fungi, 2nd Edition, Pat O'Reilly 2016, reprinted by Coch-y-bonddu Books in 2022.

Mattheck, C., and Weber, K. Manual of Wood Decays in Trees. Arboricultural Association 2003.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008.

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi.

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