Chalciporus piperatus, commonly known as the peppery bolete, is a small pored mushroom of the family Boletaceae found in mixed woodland in Europe and North America.

The genus Chalciporus was an early branching lineage in the Boletaceae and appears to be related to boletes with parasitic properties.

Previously thought to be ectomycorrhizal (a symbiotic relationship that occurs between a fungus and the roots of various plant species), C. piperatus is now suspected of being parasitic on Amanita muscaria.

[1] It was reclassified and given its current binomial name in 1908 by Frédéric Bataille when he made it the type species of the newly circumscribed genus Chalciporus.

[8] Wolfgang Klofac and Irmgard Krisai-Greilhuber reclassified it as a variety of C. piperatus in 2006,[9] although some sources continue to regard it as a distinct species.

[11][12] One of the smaller boletes, Chalciporus piperatus has an orange-fawn 1.6–9 cm (5⁄8–3+1⁄2 in) cap that is initially convex before flattening out in age.

The basidia (spore-bearing cells) measure 20–28 by 6–8 μm and are hyaline (translucent), four-spored, and narrowly club-shaped, with many internal oil droplets.

[18] The fruit body of the North American species Chalciporus piperatoides are similar, but can be distinguished by its flesh and pores staining blue after cutting or bruising.

[22] The fungus is widespread across North America, fruiting from July to October in the eastern states and from September to January on the Pacific Coast.

[27] Chalciporus piperatus grows in conifer plantations associated with the fly agaric (Amanita muscaria) and the chanterelle (Cantharellus cibarius).

[9] Fruit bodies can be parasitised by the mould Sepedonium chalcipori, a highly specialised mycoparasite that is only known to infect this bolete.

[4][16] It has been used as a condiment in many countries, with the Italian chef Antonio Carluccio recommending it be used only to add its peppery flavour to other mushrooms.

[21] Some recommend that it be well-cooked before consumption to minimize the risk of gastric symptoms,[23] but the peppery taste is lost with cooking,[40] and even more so by reducing it to a powdered form.

[16] Sclerocitrin, a pigment compound originally isolated from the common earthball (Scleroderma citrinum), is the major contributor to the yellow colour of the mycelium and the stipe base of C. piperatus fruit bodies.

In comparison, the antimony levels detected in other common terrestrial fungi from the same area, both saprobic and ectomycorrhizal, were more than an order of magnitude smaller.