The genus Psilocybe is represented in the British Isles by a handful of species, of which two are commonly encountered and the rest are rare or localised. Psilocybe cubensis, the species behind nearly every named strain in the trade, is not among them: it is pantropical and does not occur naturally in Britain.
The most frequently encountered Psilocybe in the UK, and one of the most distinctive fungi in the British flora. A small, conical to sharply papillate cap on a slender, wavy stem, in grassland, typically autumn.
Spores are dark purple-brown, ellipsoid, and around 12-14 by 7-8 micrometres, smaller and narrower than cubensis. The cap's separable gelatinous pellicle is the classic macroscopic character.
A wood-chip and mulch species, increasingly common in urban plantings, fruiting late in the year. The cap is markedly wavy at maturity, chestnut when moist and fading dramatically as it dries.
Spores are dark purple-brown, ellipsoid and larger than semilanceata at roughly 9-12 by 6-8 micrometres. It bruises blue readily, which semilanceata does far less obviously.
This is the section that belongs on every page of this kind. The genus Galerina contains species that fruit in similar habitats and superficially resemble small brown Psilocybe species. Galerina marginata contains amatoxins, the same class of compound as the death cap, and poisoning is frequently fatal.
The spore print separates them immediately: Galerina prints rust-brown, Psilocybe prints dark purple-brown. This is precisely the kind of question spore microscopy exists to answer, and it is the reason a spore print is the first thing any serious identification asks for.
No description on a web page is a substitute for competent identification. If you cannot confirm a specimen from its microscopic characters, you have not identified it.
Fungus containing psilocin is a Class A drug in the UK under the Misuse of Drugs Act 1971 as amended, whether fresh, dried or prepared in any way. Picking or possessing these species is therefore an offence. The spores of Psilocybe species are a separate matter and are not controlled, which our UK law guide explains.