Sandy Stiltball

The Sandy Stiltball is one of the most curious of the stalked gasteroid fungi. A tall, rigid, woody stalk covered in coarse shaggy scales rises from a persistent membranous sac buried in sand, and at its top sits the spore case. In young specimens the case is a rounded head; as it matures the upper skin splits away all round and falls off like a lid, leaving a flattened, cushion-like disc of rusty-brown powder perched on the stalk.

The genus Battarrea is placed in the Agaricaceae and is adapted to dry, exposed sites where a soft fleshy fruiting body could not survive. Everything about it is built for durability: the woody stalk, the tough volva, and a spore mass mixed with distinctive spiral-thickened elaters that help loosen the powder for the wind.

Heights of 10-40 cm are usual and exceptional specimens are taller, so the fungus can be conspicuous from some distance across bare sandy ground. Many mycologists treat Battarrea stevenii as a large form or synonym of this species.

Fruiting body

A stalked structure 10-40 cm tall. The spore case at the apex is 2-5 cm wide, at first a rounded to hemispherical head enclosed by a thin skin.

Spore case

As it matures, the upper part of the case skin splits away circumferentially and detaches, exposing a flattened, cushion-shaped or disc-like mass of rusty-brown to cinnamon powder sitting on the persistent lower half. This disc-on-a-stick silhouette is the classic mature appearance.

Stipe

Tall, straight or slightly curved, woody and fibrous, hollow-stuffed, 1-3 cm thick, covered in coarse, upturned, shaggy brown scales. It emerges from a tough, membranous, sac-like volva at ground level, usually buried in the sand and needing careful excavation to see.

Flesh and spore mass

The stalk flesh is dry, tough and woody. The spore mass is rusty brown and powdery, mixed with capillitium and with characteristic spiral-thickened elaters that spring apart as they dry. Spores in mass are rusty brown.

Grows in dry, sandy, well-drained and often nutrient-poor ground: sandy hedge banks, the sheltered base of old hedgerows and walls, sand dunes, arid scrub, dry riverbeds, roadsides and semi-desert washes. It is often associated with dry hollows near elder, elm or other shrubs whose litter enriches the sand.

The distribution is scattered but nearly worldwide in warm and temperate dry regions, including parts of Europe (where it is uncommon and localised), the southwestern United States and Mexico, the Mediterranean basin, central Asia, southern Africa and Australia. Fruiting is mainly in autumn, and the woody stalk with its spent disc can stand through winter.

Battarrea phalloides is saprotrophic, its mycelium living deep in sandy soil where it breaks down buried plant debris and accumulated organic material. Because the substrate is poor and dry, the fungus may take years to build up enough reserves to fruit, which helps explain why it appears sporadically and often in the same few spots.

Dispersal is entirely passive and wind-driven. Once the case lid falls away, the exposed disc of powder is scoured by wind, aided by the elaters that twist and flick as humidity changes, working spores loose from the mass. The tall stalk lifts the disc into moving air above the sheltered ground layer.

Podaxis pistillaris shares the arid habitat and shaggy look, but its spore case stays as an elongate, closed whitish capsule that splits lengthwise, its spore mass is blackish-brown, and it has no membranous volva at the stalk base. Tulostoma stalkballs are far smaller, with a spore sac barely a centimetre wide opening by a neat tubular mouth, and their slender stalks lack the coarse shaggy scales.

Stinkhorns of the genus Phallus also emerge from a sac at the base, but their stalk is soft, hollow and spongy rather than woody, and the head carries a slimy olive-green spore layer instead of dry rusty powder. Weathered Battarrea stalks with the disc gone can resemble a woody twig and are easily overlooked.