Liberty cap mushroom: the name, history and research of Psilocybe semilanceata

Few mushroom names have a stranger back story than “liberty cap.” It sounds like a brand or a variety, yet it is neither. It is an English common name that belongs to one scientific species, Psilocybe semilanceata, and it comes from a political symbol that is more than two thousand years old.

This guide follows the paper trail: where the common name came from, what the scientific name records, one landmark 1969 chemistry paper, and a recent genome paper. For each, it says what the source supports and what it does not. Species names and common names are different things, and neither one can tell you what an unknown mushroom is. For the wider landscape of labels, see our directory of magic mushroom species and names and the pillar guide.

What is the liberty cap mushroom?

Psilocybe semilanceata is the scientific name. “Liberty cap” is the common name the NCBI Taxonomy record lists for it. That record, number 181775, gives the full name as Psilocybe semilanceata (Fr.) P. Kumm., 1871, with the rank “species.” The authority in brackets, Fr., is the Swedish mycologist Elias Fries; P. Kumm. is the German mycologist Paul Kummer.

A recent genome paper also calls it the type species of the genus Psilocybe (Bollinger et al., 2025). In plain terms, it is the species the genus is built around.

So neither “liberty cap” nor Psilocybe semilanceata is a strain, cultivar or commercial category. Those words belong to a different naming question, which we cover in our guide to cubensis names and how to research origin stories.

Where does the name “liberty cap” come from?

The most detailed answer is a peer-reviewed paper in the journal Folklore by the historian Adrastos Omissi (Omissi, 2016). It traces the name to the cap of liberty, a symbol with a long history. In ancient Rome, a freed slave was given a brimless felt cap, the pileus, as a sign of freedom, and Roman writers used the word to mean “freedom” itself. The symbol was revived in early modern Europe and became famous in the American and French revolutions.

Omissi then follows the link to fungi through a few written steps. He argues the mushroom comparison appears in a poem by James Woodhouse, written in 1787 and printed in 1803, which likens mushrooms to “Freedom’s cap.” In 1812, Southey and Coleridge’s Omniana carried a passage about a common fungus as a “mushroom cap of liberty.” Omissi thinks Coleridge probably took the idea from Woodhouse, whom Southey knew (Omissi, 2016).

By Omissi’s account, the common name “Liberty Cap” then entered mycology books in the later 1800s, always for Psilocybe semilanceata. He says its first such use was perhaps in Mordecai Cooke’s 1871 Handbook of the British Fungi, and notes Cooke’s later use of the phrase in quotation marks in 1894.

One popular explanation does not survive the dates. Omissi notes that a claim that the name comes from French First World War helmets “is impossible,” because the name predates that war by nearly 130 years (Omissi, 2016). That is a good example of why this site checks stories about names against records. We did the same in our guide to origin stories.

A caution on scope. This is the best-documented account we found, but it is one scholar’s reconstruction from printed sources, and it is about English usage. It does not tell you anything about how the mushroom is named in other languages or in other communities.

What does the scientific name Psilocybe semilanceata record?

Index Fungorum, a register of fungal names, lists Psilocybe semilanceata (Fr.) P. Kumm. as published in 1871 in Kummer’s book Führer in die Pilzkunde, with status “Legitimate” and as the current name (Index Fungorum record 232492). Its linked basionym record is Agaricus semilanceatus Fr., published in 1818 in Fries’s Observationes mycologicae, page 178 (Index Fungorum record 454300).

A basionym is the earlier name on which a later combination is based. Here, Kummer moved the old species from the huge genus Agaricus into Psilocybe, and the two records are one naming history, not two marketed varieties. Omissi describes the same change (Omissi, 2016).

Names can also gather other labels. NCBI lists Panaeolus semilanceatus (Fr.) J.E. Lange, 1936 as a synonym built on the same original name, and marks it as an illegitimate name (NCBI Taxonomy). Knowing the old combinations helps when you search older literature, which may use an earlier genus. It does not follow that every old identification was right: a name record and the identity of a particular specimen are separate questions.

What did the 1969 Mantle and Waight paper report?

The bibliographic record is clear: P. G. Mantle and E. S. Waight, “Occurrence of psilocybin in the sporophores of Psilocybe semilanceata,” Transactions of the British Mycological Society 53(2): 302–304, October 1969 (Mantle and Waight, 1969). Sporophores are the mushrooms’ fruiting bodies. Omissi describes the paper as establishing that the British-growing liberty cap contained psilocybin, a compound first isolated from Mexican mushrooms in 1958 (Omissi, 2016). For psilocybin itself, see what is psilocybin.

We could not open the full text, which is behind a paywall. So we do not describe its methods, its samples or any amounts. We also do not repeat the draft’s statement about where the material came from, because we could not check it. What the record does support is a publication date and a subject.

That date answers one question only: when this result was published. It does not mark when the species first existed, was first noticed by people or was first used. Those would be different historical claims needing different sources. Later papers with titles such as “The Content of Psilocybin in Norwegian Psilocybe semilanceata” (Christiansen et al., 1981), “Psilocybin in Finnish Psilocybe semilanceata” (Jokiranta et al., 1984) and “The Occurrence of Tryptamine Derivatives in Psilocybe semilanceata” (Brenneisen and Borner, 1988) show that the work continued. We checked only their titles and bibliographic details, and we draw no numbers from them.

One measurement from particular material is a historical chemistry reference. It is not a guide to use and it is not a fixed potency for the species. Our guide to what lab studies can and cannot establish about potency explains why.

What do genome papers add to the research record?

In December 2024 (in the February 2025 issue), Ian Bollinger and colleagues published draft genomes for five Psilocybe species in Microbiology Resource Announcements: P. semilanceata, P. gandalfiana (a provisional name), P. caeruleorhiza, P. azurescens and P. allenii. The stated aim was to allow deeper study of the psilocybin gene cluster and to improve the taxonomic resolution of the genus (Bollinger et al., 2025).

For P. semilanceata, the sequenced culture was a single-spore-derived culture (a monokaryon) from a wild collection on the Clatsop County coast of Oregon, USA. The authors report that its psilocybin gene cluster looked most similar to that of Psilocybe mexicana (Bollinger et al., 2025). The paper is dated 2025 by its issue but first appeared online at the end of 2024.

A genome resource like this supports questions about genes and relationships. It does not directly establish anything about a human experience, and a single sequenced culture does not describe every population of the species.

Is a liberty cap a strain, and how is it different from names like Golden Teacher?

No. Liberty cap is a common name for a wild species. Names such as Golden Teacher are labels used for cultivated lines of a different species, Psilocybe cubensis, and they answer a different question (see Golden Teacher: the name and the research). Putting them side by side in a list of “varieties” would imply they are the same kind of thing, and they are not.

Why does this page not describe how to recognise it?

Because a few visible traits can sound like a safe-consumption test, and they are not one. A responsible description would need a checked taxonomic source and review by a specialist mycologist, and we have not had that review. Leaving the description out is better than offering an unverified shortcut. Photographs and general descriptions have real limits, which our safety page discusses.

What we could not verify or still don’t know

• What the 1969 paper’s methods, sample origins and measurements were. We could not read the full text.
• Who first used “Liberty Cap” as a printed common name. Omissi says “perhaps” Cooke in 1871, and an earlier use may exist.
• Whether the species’ current treatment will stay unchanged. The two registers we checked agree today, but a mycologist should confirm the position before this article is treated as settled.
• What any later chemical analysis found. We checked only titles, not contents.

The short version: the common name is a borrowing of an ancient symbol that reached mycology books in the 1800s, the scientific name is a documented 1818 to 1871 naming history, and the research record is a set of separate papers, each answering a narrower question than the name might suggest. For the larger story, read our history of magic mushrooms.

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