Cedar Cup

Cedar Cup is a spring fungus of very particular habitat: it grows in the soil beneath cedar trees, and is rarely found anywhere else. The fruiting body develops almost entirely underground as a hollow brown ball, then pushes up to the surface and splits the top into pointed, star-like lobes, revealing a smooth pale grey to whitish inner surface that contrasts sharply with the dark, coarsely hairy exterior.

Geopora is a genus in the Pyronemataceae whose members characteristically begin hypogeous (underground) and open only partially, giving them a half-buried, earth-encrusted appearance. G. sumneriana is the largest and most conspicuous European member.

The strong host link makes it one of the easier cup fungi to find deliberately: churchyards, parks and large gardens with mature cedars are the places to search in late winter and early spring.

Fruiting body

A deep cup 2–8 cm across, developing below ground as an almost closed hollow sphere and later erupting so that the upper part clears the soil. The rim splits into 4–8 irregular pointed lobes or rays that curve outward, giving a star-like or torn appearance. Much of the body remains buried, so an apparently small cup often proves to be twice as deep once excavated.

Inner surface

Smooth, matt and pale — whitish, cream or pale grey, sometimes faintly buff — providing a strong contrast with the outside.

Outer surface

Dark brown, densely covered in coarse, stiff brown hairs that trap soil particles and root fragments, so the exterior usually appears encrusted with earth. Cleaning a specimen reveals the hair layer clearly.

Flesh and spore print

The flesh is thin, brittle and pale brownish, without colour change when broken. Spores are colourless, smooth and broadly elliptical, often with large oil droplets; a deposit is whitish. Fruiting bodies are usually scattered or in small groups, sometimes in a rough arc following the roots of the host tree.

The species grows in soil under cedars (Cedrus species — Cedar of Lebanon, Atlas Cedar and Deodar), typically within the drip line of large planted specimens in churchyards, parks, cemeteries, avenues and estate gardens. Well-drained, often calcareous or chalky soils are preferred, and the fungus frequently reappears in the same spot for many years.

The season is early: late winter through spring, principally February to May in temperate Europe, when the soil is moist but before the summer drought. Because Cedrus is a planted exotic across most of Europe, the fungus is largely an urban and parkland species there; it is also recorded around the Mediterranean and in parts of Asia within the natural range of its hosts.

Geopora sumneriana is considered ectomycorrhizal, forming a symbiotic sheath around the fine roots of cedar. The fungus supplies the tree with water and mineral nutrients drawn from a much larger soil volume than the roots alone could exploit, and receives sugars in return, which explains the exclusive association with a single host genus and the tendency for fruiting bodies to follow root runs.

The hypogeous early development protects the young fruiting body from frost and drying in a season when surface conditions are hostile. Only when the fertile inner surface is mature does the cup rupture the soil and split open, exposing the hymenium for a short, well-timed period of spore discharge.

Geopora arenicola and G. arenosa are much smaller, similarly half-buried hairy brown cups but grow on sandy soil, dunes and bare paths without a cedar association. Sepultaria-type species in the same complex differ chiefly in size and spore dimensions.

Sarcosphaera coronaria also begins underground and splits into a crown of rays, but its inner surface is lilac to violet rather than whitish and it is associated with beech and conifers on chalk, not cedar. Peziza species are sessile surface cups without a coarse brown hairy exterior and never begin fully buried. Humaria hemisphaerica has a whitish interior and brown-hairy outside too, but it is smaller, sits on the surface of soil or rotten wood, and does not develop underground or split into rays.