Genus at a glance
| Field | Detail |
|---|---|
| Classification | Genus, sometimes treated within Panaeolus |
| Family | Bolbitiaceae |
| Described species | Around 10 |
| Spore print | Dark brown to black, with roughened, ornamented spores |
| Distribution | Cosmopolitan, common in lawns and grassland |
| Habitat | Grassy soil, lawns, occasionally dung |
| Key alkaloids | Trace psilocybin and psilocin reported in some species, debated |
Overview
Panaeolina is a small genus split from Panaeolus on a microscopic character: its spores are ornamented, or roughened, rather than smooth. To the naked eye a Panaeolina looks much like a small Panaeolus, and the two are often discussed together, but the spore ornamentation is consistent enough that many mycologists keep them separate. The best-known species, Panaeolina foenisecii, the "mower's mushroom" or "lawn mower's mushroom," is one of the most common lawn fungi in the temperate world, which is exactly why it matters here.
Panaeolina foenisecii has long been the subject of debate over whether it contains psilocybin. Reports are inconsistent: some analyses have found trace psilocybin and psilocin, others none, and the presence of serotonin and related indoles complicates the chemistry and the older reports. The result is a genus whose flagship species has an unsettled, contested status, hovering at the boundary between "weakly active" and "not active at all."
Because it is so abundant in the lawns where children and pets roam, Panaeolina foenisecii is a frequent subject of poison-control calls, usually with little or no effect. Its significance in the index is therefore double: it is a genuinely marginal and contested psilocybin candidate, and it is one of the most commonly encountered and misidentified small lawn mushrooms in the temperate world.
Documented species
| Species | Notes | Distribution |
|---|---|---|
| P. foenisecii | The "mower's mushroom"; trace or variable psilocybin reported, often none | Cosmopolitan |
| P. castaneifolia | Reported variable indole content | Temperate |
Ecology and identification
Panaeolina species are small, slender lawn and grassland mushrooms with conical to convex caps that are often hygrophanous, changing colour markedly as they dry, and sometimes showing a banded or zoned appearance as they lose moisture. The gills mature to a dark, mottled brown, echoing the Panaeolus pattern, and the spore print is dark brown to blackish. The defining feature, the roughened spore surface, is visible only under a microscope.
The genus grows in grassy places, especially mown lawns, sports fields, and pastures, appearing scattered or in troops after rain. Panaeolina foenisecii in particular is so common in domestic lawns that most people in temperate regions have walked past it many times. Its small size, dull colours, and hygrophanous colour shifts make it easy to overlook and easy to confuse with a range of other small brown lawn mushrooms.
Field-level identification places a mushroom in the Panaeolus and Panaeolina group by its dark mottled gills and dark spore print, but separating Panaeolina from Panaeolus, and confirming the species, requires microscopy to see the spore ornamentation. This is a genus where the naked eye simply cannot resolve the questions that matter.
Chemistry and potency
The chemistry of Panaeolina is the reason it sits at the edge of the index. Panaeolina foenisecii has produced contradictory results across decades of analysis: some studies report trace psilocybin and psilocin, others find none, and the picture is muddied by the presence of serotonin and related indole compounds that are not psychoactive in the same way. The variation may reflect genuine differences between populations, seasons, and growth conditions, or differences in analytical methods, or both.
The practical upshot is that Panaeolina foenisecii cannot be described as a dependable psilocybin mushroom. At most it is marginally and inconsistently active, and by many accounts not meaningfully active at all. This makes it a valuable illustration of a subtle point: "psychoactive" is not a simple binary label but a question of which population, which season, and which assay, and some mushrooms genuinely sit on the boundary.
Safety and look-alikes
Because Panaeolina foenisecii is so abundant in domestic lawns, its main practical significance is as a mushroom that children and pets encounter and that prompts anxious poison-control calls. In the great majority of cases little or no harm results, but the genus shares its habitat with other small brown lawn mushrooms, some of which are toxic, so the general caution about small-brown-mushroom confusion applies.
The genus is included here for completeness and because it is so frequently encountered and misidentified, not because it is a source of psilocybin worth seeking. As with every entry in the index, this is documentation of what the genus is, not guidance on handling or consuming it.
Where the science stands
Panaeolina is a small, under-studied genus whose flagship species has produced contradictory chemical results for decades. That inconsistency is itself the scientifically interesting fact: it is a reminder that psychoactivity is not always a clean yes-or-no property and that a single widespread species can straddle the line. Whether Panaeolina foenisecii should be considered a psilocybin mushroom at all remains genuinely unsettled, and the rest of the genus is barely characterised.
Its place in the index is as the clearest example of a borderline case, a common, contested, marginally active lawn mushroom that shows how blurry the edge of the psilocybin world can be. It rounds out the picture precisely because it refuses to fit neatly into either the "active" or the "inactive" column.
What "borderline" really means
The long argument over Panaeolina foenisecii is worth dwelling on because it exposes how a simple question, is this mushroom psychoactive, can resist a simple answer. Several factors pull the results in different directions. Psilocybin, where present, may occur at very low and variable concentrations, close to the detection limits of older analytical methods, so that whether a study finds it can depend as much on the technique as on the mushroom. Different populations, growing in different soils, climates, and seasons, may genuinely differ in what they contain. And the presence of serotonin and related indoles, which are chemically similar but not psychoactive in the same way, can complicate both the chemistry and the interpretation of effects.
There is also the matter of human reports. Because Panaeolina foenisecii is so abundant in lawns, it is eaten accidentally more often than most wild mushrooms, and the resulting anecdotes range from no effect at all to mild disturbances that are hard to attribute confidently to psilocybin rather than to ordinary gastrointestinal upset or to expectation. This messy body of evidence is exactly what a genuinely borderline case looks like: not a clean signal obscured by poor measurement, but a real biological variability that resists being forced into a yes-or-no box.
For the index, Panaeolina is valuable precisely because it does not resolve neatly. It stands as a corrective to the tidy impression that mushrooms can be sorted cleanly into active and inactive, and it shows that at the margins the honest answer is often "it depends, and the science is not settled." That humility is itself part of an accurate picture of the psilocybin world.