Never eat a wild mushroom identified only from a website, a book or an app. Have every find checked in person by an expert, such as a mycological society.
Identification
The charcoal burner is a medium to large, firm brittlegill with a cap that can show almost any mixture of violet, purple, slate-blue, grey-green or olive, often in patches on the same cap. The cap skin is smooth, slightly greasy when moist and peels back for about half of the radius. The gills are white, crowded and attached to the stem.
The single most useful field character is the texture of the gills: in most Russula species they are brittle and shatter when you run a finger across them, but in R. cyanoxantha they are flexible, elastic and feel greasy or waxy. The stem is white, firm, sometimes tinged with violet, and has no ring and no sack-like volva at the base. The flesh is white and the taste mild, not peppery.
A classic chemical test is iron sulphate (FeSO4) on the stem: most brittlegills turn pinkish-orange, whereas the charcoal burner shows no reaction or only a faint greenish tint. The spore print is white, and the spores are ornamented with warts that stain blue-black in Melzer's reagent.
A green form, sometimes named var. peltereaui, can be entirely green and is the one most easily confused with dangerous species.
Habitat and ecology
Russula cyanoxantha is an ectomycorrhizal fungus that forms partnerships with the roots of beech (Fagus), oak (Quercus), sweet chestnut and sometimes conifers. It is common in broadleaf and mixed woods across Europe, on a wide range of soils, and fruits from early summer to late autumn, often among the first Russulas of the season.
Uses and importance
The charcoal burner is widely regarded as one of the best edible Russulas. Its firm flesh holds its shape during cooking and has a mild, nutty taste. It is usually sautéed, grilled or added to mixed mushroom dishes. As with other brittlegills, young firm specimens are preferable, as older ones are often infested by insect larvae.
Safety and edibility
Russula cyanoxantha is edible when correctly identified and cooked. Never eat a wild mushroom based on a website, an app or a photo: have every collection checked in person by an expert, such as a mycological society or a trained mushroom adviser. The most serious risk is confusing green or olive forms with the death cap (Amanita phalloides), which causes potentially fatal liver failure. Always dig up the entire stem base to check for a volva, and look for a ring on the stem. Never pick mushrooms by cap colour alone.
Some other Russula species are acrid and cause vomiting and diarrhoea. The traditional tasting test should only be practised under expert guidance, never on mushrooms that might be Amanita, and the sample must be spat out.
If you suspect mushroom poisoning, call your local emergency number or poison centre straight away, even before any symptoms appear, and keep the remains of the mushrooms.
Look-alikes
Death cap (Amanita phalloides): olive-green to yellowish cap with radial fibres, white free gills, a ring on the stem and a membranous sack-like volva at the base; brittlegills never have a ring or volva. Sickener (Russula emetica) and other acrid species: often red cap, brittle gills and an intensely peppery taste. Russula heterophylla and R. aeruginea (green brittlegills): similar colours but brittle gills; R. heterophylla reacts orange with iron sulphate. Russula virescens has a cracked, verdigris cap and is also edible.
Around the world
The charcoal burner is widespread in Europe, and similar species occur in North America and Asia, so names and edibility information from one region should not be assumed to apply to look-alikes elsewhere. Green brittlegills share woods with the death cap in many regions, which is why foragers are taught to always check the base of every mushroom.
