Crowned Earthstar

The Crowned Earthstar is a sturdy, dark-toned member of Geastrum found in rich woodland soils and shaded banks. Its outer wall splits into a broad star of pointed rays that bend well back, often arching until the fruit body is pushed slightly up out of the litter, while the inner spore sac is held on a short but unmistakable stalk.

The sac itself is the best colour cue in the genus: dark grey-brown to almost slate, frequently overlaid with a fine pale bloom or pruina that rubs away to leave a smoother, darker surface. Above the stalk sits a small swollen apophysis, a collar-like thickening where sac meets stalk, and the whole is topped by a conical mouth built of fine converging fibres with no grooves or furrows.

As with all earthstars, the fruit body starts as a buried onion-shaped ball covered in a felt of mycelium and soil, and only reveals its structure when the outer layer tears. Mature specimens are tough and persist well after the spores have gone.

Star and rays

Expanded fruit bodies are 3–8 cm across. The outer peridium splits into 5–9 narrow triangular rays that recurve strongly and may lift the centre of the fungus off the ground. The inner surface of the rays is buff to dull brown, sometimes cracking into a mosaic with age; the outer surface is felted and encrusted with soil and litter.

Spore sac and stalk

The sac is 1–2.5 cm across, globose to broadly egg-shaped, and distinctly dark: grey-brown, purplish-grey or nearly slate, usually with a fine whitish bloom when fresh. It sits on a short, stout, pale stalk 2–5 mm long, with a small apophysis — a ring-like swelling — immediately beneath the sac.

Peristome

The mouth is conical to shortly beaked, silky-fibrillose with converging fibres, and is not furrowed. It may be slightly paler than the sac but is not enclosed within a sharply outlined circular court.

Interior

The gleba is white and firm in immature specimens, ripening to fine dark brown spore powder around a central columella. The sac wall is thin and papery, so a raindrop strike is enough to expel a puff of spores.

The Crowned Earthstar grows on humus-rich, often calcareous soils in broadleaf woodland, shaded hedge banks, coppice, parkland, dune scrub and shrubberies. It shows a liking for warm, well-drained ground with a deep leaf-litter layer, and is also found in old gardens and churchyards.

Fruiting is mainly autumn, continuing into early winter, and weathered fruit bodies persist much longer. It is widespread but rather local across Europe, and is also recorded from North America, North Africa and Asia, generally in lowland warm-temperate districts.

This species is saprotrophic, decomposing leaf litter, humus and fine buried woody debris. Its mycelium binds the upper soil into a felted layer, fragments of which remain attached to the outside of the rays after expansion.

The stalked sac raises the mouth clear of the litter, and spore release follows the standard earthstar bellows mechanism: each drop of rain or brush of a passing animal compresses the thin sac and drives a puff of dark spore powder out of the fibrous mouth into moving air.

The Beaked Earthstar (Geastrum pectinatum) shares a stalked sac and apophysis but has a long, conspicuously grooved, beak-like mouth and a longer stalk, while G. coronatum has a silky, ungrooved mouth. The Striated Earthstar (Geastrum striatum) also has a grooved beak plus a flaring collar under the sac, both absent here.

The Rounded Earthstar (Geastrum saccatum) and Fringed Earthstar (Geastrum fimbriatum) are separated instantly by their sessile sacs with no stalk, and both are paler. The Arched Earthstar (Geastrum fornicatum) has rays fused at their tips to a separate basal cup so the fungus stands vaulted on legs, which G. coronatum never does.