Quick facts

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

What do King Alfred's cakes look like?

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.

Where to find King Alfred's cakes

King Alfred’s cakes are common and widespread in the UK. You can spot them in deciduous woodland in groups on dead and decaying wood, especially fallen beech and ash branches.

King Alfred's cakes with white-lipped banded snail on

Credit: Sabena Jane Blackbird / Alamy Stock Photo

Value to wildlife

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.

Did you know?

King Alfred’s cakes are also known as 'cramp balls' as it was believed that carrying them would protect people from attacks of cramp.

Mythology and symbolism

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.

King Alfred's cakes on tree

Credit: Stephen Hyde / Alamy Stock Photo

Uses of King Alfred's cakes

Mature specimens of King Alfred's cakes are useful as tinder for fire lighting. They burn slowly, much like a charcoal briquette, but with a particularly pungent smoke.