KingdomFungiGenusClitocybeSpeciesdealbata
Clitocybe dealbata
T3 · LethalPublished 2026-10-19Summer / Autumn
This is the species that kills people who are confident, and it does so because it looks like nothing in particular. It is a small white mushroom in a lawn. It has no distinctive smell, no distinctive colour and no distinctive shape. It contains muscarine, it grows within a metre of a harmless species that people collect on purpose, and the gap between the two is a stem that either bends or snaps.
Block 01 · Record
The stem test and the gills
Pick the fruit body and try to wind the stem around your index finger. Clitocybe dealbata has a fibrous, brittle stem that cracks and breaks as soon as you bend it past about thirty degrees. Marasmius oreades, growing in the same turf, has a stem that winds around the finger and springs back without damage. Back it up with the gills: C. dealbata has crowded thin gills touching each other at the cap margin with no gaps, while M. oreades has thick, waxy, widely spaced gills with visible gaps as wide as the blades. Both tests are free, and both should be run on every specimen, not on one representative.
Spores and the reason to use black paper
The spore print is white and thin, and on white paper it is easy to miss entirely — use a black card. Spores are only 4.5-6 x 3-4 micrometres, ellipsoid, smooth, thin-walled, inamyloid, with a small hilar appendix and no germ pore. They are among the smallest spores of any grassland agaric in this collection, and measuring them requires 1000x and a calibrated eyepiece. The very small size is a useful cross-check against Clitopilus prunulus, whose spores are 9-12 micrometres and ribbed.
Turf, troops and rings
Clitocybe dealbata is a saprotroph of short grass and it fruits in troops, sometimes in partial or complete rings, in lawns, pasture, playing fields, verges and churchyards. It often occupies the same square metre as Marasmius oreades and the two can be intermingled within a single tuft. In temperate Europe the season runs from July to November with a peak in September and October, though it can appear in any month after sustained rain.
Muscarine and the cholinergic crisis
Muscarine is a direct agonist at peripheral muscarinic acetylcholine receptors, and the resulting syndrome has a latency of fifteen minutes to two hours: sweating, salivation, lacrimation, blurred vision, abdominal cramps, vomiting, diarrhoea and bradycardia, with bronchospasm and hypotension in severe cases. The classical mnemonic covers the secretory symptoms but not the cardiac ones, and the cardiac ones are what kill. Onset from a single small mushroom can be severe in a child or in an adult on beta blockers, and the dose needed to reach a life-threatening bradycardia is not far above the dose that causes sweating.
Points to carry to the bench
- The stem is fibrous and snaps when bent past about 30 degrees; Marasmius oreades in the same turf bends and springs back.
- Gills are crowded and touching, not widely spaced and waxy; spores are only 4.5-6 micrometres.
- White thin spore print — use black paper, or the deposit will be missed entirely.
- Muscarine syndrome at 15 min to 2 h: secretions plus bradycardia, and the bradycardia is what kills.
| Cap | shape: Convex to plane, often slightly depressed at the centre, 20-40 mm across; the margin is inrolled at first and then wavy and irregular.surface: White to ivory with a waxy sheen that is characteristic of the genus; dry, smooth, and sometimes with a very faint grey bloom at the centre.margin: Inrolled then wavy, faintly translucent-striate when wet and drying smooth. |
|---|---|
| Gills | attachment: Adnate to subdecurrent, running a short distance down the stem — enough to be visible from the side, but far less than in Clitopilus prunulus.spacing: Crowded, 3-4 gills per millimetre, touching each other at the cap margin with no visible gaps.edge: Entire, thin and concolorous; the gills stay white at every age. |
| Spore print | Ellipsoid, smooth, thin-walled, with a small hilar appendix and no germ pore.Smooth and inamyloid; the spores are small even by Clitocybe standards and should be measured at 1000x. |
| Habitat and season | Saprotrophic in short grass: lawns, pasture, playing fields, verges, churchyards and the mown edges of tracks. Fruits in troops and in partial or complete rings, often in the same turf as Marasmius oreades and frequently within a metre of it. |
Block 02 · Chemistry
| Reagent | Verdict | Reaction | Weight |
|---|---|---|---|
 MELZ | inamyloid | Spore wall stays pale; no blue-black development at any magnification. | 3.00 |
 KOH5 | negative | Cap shows no reaction whatever; the white pigment is stable to alkali, unlike that of some pale Clitocybe species which yellow. | 2.00 |
 FESO4 | negative | Flesh unchanged after 60 s. | 3.00 |
 ANIS | negative | No change on cap or flesh; the white of the fruit body is unaffected at thirty minutes. | 2.00 |
 COTTON | acyanophilic | Spores remain unstained and appear as clear outlines. | 2.00 |
Injury stain None. Cap, gills and stem keep their colour when cut. This absence of any bruise reaction is shared with every harmless pale grassland agaric and therefore carries no information — the identification is made on the stem and the gills, never on the cut surface.
Block 03 · Confusion
| Separating character | This record | Confused with |
|---|---|---|
| A tough stem that twirls around a finger and springs back, widely spaced thick waxy gills with gaps between them, and a hygrophanous buff cap. The stem test takes two seconds. | Clitocybe dealbataT3 | Marasmius oreades▲ +3 |
| A pink overnight spore print and deeply decurrent gills, plus a strong mealy odour; C. dealbata has a white deposit, shallow subdecurrent gills and no distinctive smell. | Clitocybe dealbataT3 | Clitopilus prunulus▲ +3 |
| Treated as the same hazard, separated on a white bloom on the cap surface and slightly larger stature; the pair is regarded by several authors as one variable species. | Clitocybe dealbataT3 | Clitocybe rivulosa▲ +0 |
Toxicity ladder
A single meal of a normal-sized fruit body has killed, or the toxin class (amatoxins, orellanine, gyromitrin, severe muscarine load) is documented as lethal in humans. T3 does not mean every meal kills — it means the margin between a meal and a fatal dose is not wide enough to plan around, and there is no field test that measures it.
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