Scaly Earthball
Scleroderma verrucosum
Also called warted earthball, scaly-stemmed earthball
A tan to ochre earthball whose thin, finely scaly skin sits on an unusually long, furrowed rooting stalk. The interior ripens from white to a dusty blackish-brown spore mass.
Overview
The Scaly Earthball is one of the more slender members of Scleroderma, a genus of gasteroid fungi in the Sclerodermataceae that produce closed, roughly spherical fruit bodies with no gills, pores or opening until the skin finally tears. Where most earthballs squat directly on the ground, S. verrucosum is distinguished by a well-developed sterile base drawn out into a stalk-like stem, so the fertile head appears propped up above the soil surface.
The outer wall, called the peridium, is comparatively thin in this species — often barely a millimetre or two — and is broken up into small, flattened, darker warts and scales that give the fungus its name. As the spores mature the head loses firmness and eventually splits irregularly across the top, weathering away to leave a ragged bowl on a persistent stalk.
Because it is common in warm, sandy woodland and on disturbed ground, the Scaly Earthball is a familiar late-season sight around park trees and along woodland tracks, often appearing in loose troops rather than singly.
How to identify it
Fruiting body
The head is 2–5 cm across, roughly globose to somewhat flattened or pear-shaped, pale ochre to yellow-brown or dull tan. The surface is dry and matt, patterned with small, low, darker brown warts and adpressed scales that are finest near the base and coarser over the top.
Wall and spore mass
Cutting the head vertically shows a thin peridium, typically 1–2 mm thick, that is white in section with a pallid or faintly pinkish tint. The interior is firm and white when very young, then passes through olive-grey and purplish-grey marbling before ripening to a powdery blackish-brown spore mass. At maturity the top of the ball splits in an irregular star-like or slit tear rather than opening by a neat apical pore.
Stalk
The base is drawn out into a distinct pseudostipe 1–5 cm long, wrinkled or grooved lengthwise, paler than the head and often sterile and chambered inside. It tapers into a mass of pale rhizomorphs — cord-like mycelial strands binding sand grains and litter — which makes the fungus feel firmly anchored when lifted.
Flesh and spores
The sterile stalk tissue stays whitish and does not change markedly on exposure. Spores are dark brown in mass, globose and spiny under the microscope, and are released as dust when the weathered head is disturbed by rain or a footfall.
Where and when it grows
The Scaly Earthball favours light, sandy or gravelly soils in broadleaf woodland, parkland, hedge banks, dune slacks and the grassy edges of woodland paths. It is regularly found under oak, beech, birch, lime and sweet chestnut, and is also common on disturbed ground such as track sides and old spoil banks where mineral soil is exposed.
Fruiting runs mainly from mid summer into late autumn, peaking after warm, wet spells. The species is widespread across Europe and North America and has been recorded from temperate and warm-temperate regions on several continents, generally at lower elevations than the more montane earthballs.
Ecological role
Scleroderma verrucosum is ectomycorrhizal, forming sheathing root partnerships with broadleaf trees. Its hyphae wrap the fine root tips of oak, beech, birch and their relatives, passing water and mineral nutrients — particularly phosphorus — into the root in exchange for sugars produced by the tree. The extensive rhizomorph network at the stalk base is part of this soil-exploring system.
Spore dispersal is passive: rather than being shot away, the dark spore dust is puffed out or washed from the ruptured head, and the tough sterile stalk can persist for weeks after the fertile tissue has blown away, marking where the fungus fruited.
Similar species
The Common Earthball (Scleroderma citrinum) is squatter and effectively stalkless, with a much thicker peridium — often 2–5 mm — broken into coarse, angular, wart-like scales, and it is a brighter dirty yellow. The Leopard Earthball (Scleroderma areolatum) is similar in size but has small dark scales each ringed by a pale halo, giving a spotted appearance, and a shorter stalk. The Potato Earthball (Scleroderma bovista) has a nearly smooth to finely cracked, pale surface rather than distinct warts.
True puffballs such as Lycoperdon species are separated by their soft, uniformly white and cottony interior when young and by the neat apical pore through which spores escape, whereas any earthball has a hard rind and an interior that darkens to purplish-black marbling before ripening.