KingdomFungiGenusSclerodermaSpeciescitrinum
Scleroderma citrinum
T1 · Gastrointestinal irritantPublished 2026-10-10Late summer / Autumn
The earthball is the species that catches people who have learned one rule — 'if it is white inside, it is a puffball' — and have not learned the second rule, which is to cut every one of them open before they go anywhere near a pan. The rind thickness and the colour of the gleba settle it in one cut.
Block 01 · Record
The cut test and what it shows
Cut the fruit body in half through the middle. A young earthball has a rind three to ten millimetres thick, leathery and warty on the outside, enclosing a gleba that is already marbled with white veins turning purple-black. A puffball of the same size has a rind under two millimetres, papery and spiny, and a uniformly white gleba with no veins. There is no third category. Because earthballs push up through banks and often sit half-buried, it is common to find both kinds within a metre of each other on the same bank.
Spores without a print
The species produces no spore print in the usual sense: the gleba matures inside the closed rind, and the spores are released only when the rind splits and weathering carries the powder away. Spores are 9-15 micrometres in diameter, globose to subglobose, thick-walled, and covered in spines up to 1.5 micrometres tall together with a partial reticulum, so the outline is strongly irregular. In Melzer's reagent the spines outline more sharply than in water, and the reaction is inamyloid — no blue-black development.
Banks, acid soils and season
Scleroderma citrinum is most abundant on acid, sandy or gravelly soils in woodland, and its substrate preference is for bare or sparsely vegetated ground: banks, cuttings, the eroded sides of ditches, track edges and the compacted soil of car parks. Fruit bodies are often partly buried and appear in groups of two to ten along the same bank, returning to the same stretch for years. The season runs from late July through November, with the strongest flush in September and early October after rain.
The syndrome and the confusion it causes
The species produces a gastrointestinal syndrome — nausea, vomiting, abdominal pain and diarrhoea beginning thirty minutes to two hours after the meal — and the syndrome is self-limiting, which is why the tier is T1 and not higher. The practical problem is the direction of the confusion: people pick earthballs believing they are puffballs, and the mistakes are made in the field rather than at the bench, because a young earthball sitting half-buried in a bank looks like a puffball until it is cut.
Points to carry to the bench
- Cut every one open: a rind 3-10 mm thick with purple-black marbled gleba means earthball, not puffball.
- No spore print — the gleba matures inside a closed rind and the spores are released only when it splits.
- Globose spores 9-15 micrometres with spines up to 1.5 micrometres and a partial reticulum.
- Grows in groups on acid banks and bare woodland soil from late July to November; T1 gastrointestinal syndrome.
| Cap | shape: No cap. The fruit body is a rounded to flattened tuber, 30-100 mm across, sometimes lobed where two fruit bodies fuse; there is no stem in the usual sense.surface: A thick, leathery rind 3-10 mm thick, ochre-yellow to brownish, covered in coarse angular warts and scales that are darker than the ground and often crack into polygonal plates.margin: Not applicable; the fruit body is closed at every stage and never opens. |
|---|---|
| Gills | attachment: None. The fertile tissue is a gleba enclosed inside the rind, divided by white veins when young and maturing into a powdery purple-black mass.spacing: Not applicable; the white veins of the young gleba are irregular and are not a gill or pore structure.edge: Not applicable. |
| Spore print | Globose to subglobose, thick-walled, with spines and a partial reticulum that make the outline strongly irregular.Spiny to reticulate with spines up to 1.5 micrometres tall; the ornamentation is best seen in Melzer's reagent or in dilute KOH. |
| Habitat and season | On acid, sandy or gravelly soils in woodland, on banks, cuttings, track edges and the eroded sides of ditches, usually where the soil is bare or sparsely vegetated. Fruit bodies are often partially buried and appear in groups of two to ten along a bank. |
Block 02 · Chemistry
| Reagent | Verdict | Reaction | Weight |
|---|---|---|---|
 MELZ | inamyloid | Spore wall and spines do not turn blue-black; the ornamentation is however outlined more sharply than in water. | 3.00 |
 KOH5 | negative | The rind darkens to a deeper brown and softens; the gleba does not change colour. | 2.00 |
 FESO4 | negative | Rind and young gleba unchanged after 90 s. | 3.00 |
 COTTON | acyanophilic | Spores remain unstained, but the spines take up a pale blue edge that makes them easier to count. | 2.00 |
Injury stain The rind browns slightly where handled, and a cut or broken fruit body releases the gleba, which stains paper and skin a durable dark brown. Any fruit body whose interior is purple-black when cut is Scleroderma; any whose interior is white and uniform when cut is a puffball.
Block 03 · Confusion
| Separating character | This record | Confused with |
|---|---|---|
| A thin, papery rind covered in conical spines that rub off, a spongy sterile base occupying the lower third, and a white, uniform gleba when young — the cut surface is the whole test. | Scleroderma citrinumT1 | Lycoperdon perlatum▲ +1 |
| A far larger, smooth, white fruit body with a thin rind and a uniform white gleba; it has no warty leathery peridium and does not grow in bankside groups. | Scleroderma citrinumT1 | Calvatia gigantea▲ +1 |
| A smaller, thinner-rinded species on a distinct rooting base, with finer and more regular warts; treated as the same hazard, and separated on rind thickness rather than on any chemical character. | Scleroderma citrinumT1 | Scleroderma verrucosum▲ +0 |
Toxicity ladder
Reproducible vomiting, cramping and diarrhoea with no hepatic, renal or neurological involvement. Onset is short and recovery is complete, but the same species can produce a severe dehydrating episode in children and in people on diuretics or beta blockers.
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