Tiny fungi with an embarrassing story, King Alfred’s cakes are named after the king’s poor baking skills. Spot them growing in broadleaf woodland where they can last for years.
Common names: King Alfred’s cakes, coal fungus, carbon fungus, cramp balls
Scientific name: Daldinia concentrica
Family: Xylariaceae
Fruiting season: year-round
Habitat: deciduous woodland on dead wood
King Alfred’s cakes look like hard, roundish lumps of coal stuck to the surface of decaying wood. The older they get, the darker they become. They don’t rot away quickly but can remain on deadwood for years.
Cap: round or cushion-shaped, 2–10 cm across and formally referred to as stroma. Matt, pinkish-brown when young, becoming black and shiny with a ‘burnt’ appearance as they age. The outer shell cracks easily.
Gills/spores: inside, the flesh is hard and a cross-section shows concentric zones of grey and black. Spores are released from the outer surface of the fungus through perithecia (small beak-like holes), leaving a darker area on the surrounding wood. Cells inside the fruit body eject the spores beyond the edge of the stroma, leaving a black spore print up to 3cm wide around the fungus.
Not to be confused with: Kretzschmaria deusta and other crust-like fungi of a similar colour. However, Kretzschmaria does not form ball or cushion-shaped growths or have concentric rings inside the fruit body.
Credit: Sabena Jane Blackbird / Alamy Stock Photo
Many kinds of insects and small animals make their home inside King Alfred’s cakes, while caterpillars of the concealer moth (Harpella forficella) are known to feed on them.
King Alfred's cakes are particularly important for the scarce fungus weevil (Platyrhinus resinosus), as the larvae live and develop within their protective walls.
King Alfred’s cakes are also known as 'cramp balls' as it was believed that carrying them would protect people from attacks of cramp.
King Alfred lived in the 9th century when parts of Britain had been overrun by Vikings. Trying to escape them, he took refuge in the home of a peasant woman who asked him to watch over her cakes, baking by the fire. He let them burn and was scolded by the woman for his negligence. It is said that embarrassed and ashamed, he scattered the cakes to get rid of the evidence. As the fungus looks like small, burnt cakes, especially as they get older, the name King Alfred’s cakes went into common use.
Credit: Stephen Hyde / Alamy Stock Photo
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