Liberty Caps A field card for Psilocybe semilanceata
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Field card No. 1 Hymenogastraceae UK: Class A since 2005 NL: Opium Act List II since 2008
Botanical drawing of a liberty cap: a slender pale stem rising from grass to a sharply conical tan cap, with a lengthwise section of the cap beside it
Plate 1. Generated illustration in the manner of a botanical drawing; not a photograph and not for identification.

Species card

The liberty cap, Psilocybe semilanceata

Psilocybe semilanceata (Fr.) P. Kumm. 1871 · liberty cap, magic mushroom

  1. 1Papilla a small pointed tip on top of the cap
  2. 2Cap conical to bell-shaped, 0.5 to 2.5 cm across, ochre to chestnut when wet, pale buff when dry
  3. 3Gills 15 to 27, pale brown darkening to purple-brown
  4. 4Stem 4.5 to 14 cm long, 1 to 3.5 mm thick, pale, often wavy, no ring
  5. 5Base in grass grows from grass roots in unfertilised pasture and lawns
  6. 6Section cap cut lengthwise, showing the narrow gills

Features as described

  • Cap sharply conical, with a papilla
  • Cap sticky when wet, from a thin gelatinous skin
  • No ring on the stem
  • Spore print dark purple-brown
  • May bruise bluish where handled
  • In grass, never on wood or wood chips

Every feature on this list is shared with at least one poisonous species. Why the description is not enough

Spore print
dark purple-brown
Habitat
unfertilised grassland, on dead grass roots
Season, Britain and Ireland
summer and autumn

Lookalikes in the same season

Several of these can kill. Amatoxin symptoms usually start more than six hours after eating.

The full comparison, with sources and documented poisonings

A key that ends in doubt

Naturalists separate species with a dichotomous key: pairs of statements that each lead on or stop. Open the couplets to see how a mycologist would reason about a small brown mushroom in grass, and where that reasoning runs out.

  1. 1Growing on wood, wood chips, mulch or compost?

    1a · Yes Outside the liberty cap's habitat. This is where amatoxin species of Galerina and Pholiotina fruit.

    1b · No, in turf Go to 2. Buried wood under a lawn cannot be seen, so this step already carries doubt.

  2. 2A ring or ring zone on the stem?

    2a · Yes Points to species such as Pholiotina rugosa or Galerina marginata.

    2b · No Go to 3. Rings are fragile and often wash away, so a missing ring proves nothing.

  3. 3Spore print rusty or snuff brown?

    3a · Yes The colour of Galerina, Pholiotina, Conocybe and Cortinarius.

    3b · Dark purple-brown Go to 4.

  4. 4Conical cap with a papilla, dark purple-brown print, in grass?

    4a · Yes Fits Psilocybe semilanceata, and equally P. pelliculosa; other dark-spored grassland species overlap. Only measured spores under a microscope separate them.

    4b · Unsure This is where every key on a screen ends.

End of key. No step here makes a mushroom safe to eat or legal to keep. Mixed collections, worn rings and weathered colours defeat every field key, and in the UK and the Netherlands picking a liberty cap to keep it is an offence.

The liberty cap is a small, slender mushroom of grassland with a sharply pointed cap, and it is the only psilocybin mushroom that grows wild in Britain in any numbers. A Swiss survey of more than a hundred European species found that it is one of just two psilocybin-containing fungi that occur in Middle and Northern Europe in quantities large enough to be collected (Stijve and Kuyper 1985). That is why it has a common name, a legal history and a long record in poison centre files.

This site explains the species. It is not a guide to finding or picking it. In the United Kingdom any fungus containing psilocin has been a Class A drug since 18 July 2005, and picking a liberty cap to keep it counts as possession. In the Netherlands the species has been named on List II of the Opium Act since 1 December 2008. The details, with the exceptions the law makes, are on the law page.

Why this card leads with the lookalikes

The real danger of the liberty cap is the other small brown mushrooms that grow in the same places. Several of them contain toxins that damage the liver or kidneys, and the first symptoms can appear many hours after eating, when it is already late. In Austria a young man looking for liberty caps ate the deadly webcap instead and lost the function of his kidneys (Franz et al. 1996). The UK's drug information service FRANK puts it plainly: the biggest danger is eating a poisonous mushroom by mistake (FRANK).

The features on this card are how mycologists describe the species. They are a summary for understanding, and they overlap with species that can kill. Separating the liberty cap from its closest relative, Psilocybe pelliculosa, takes a microscope and a measurement of the spores.

How the guide is arranged

Each entry answers one question: how the species is described and why that is not enough, which lookalikes share its grassland, where and when it appears, what is known about its chemistry, what the law says in the UK, the Netherlands and elsewhere, and how a Green Park poisoning in 1799 began its recorded history. Every entry names its sources and the date it was last checked.