Editorial
McKennaii, a Psilocybe cubensis cultivar examined
Abstract
McKennaii is the trade name of a cultivated line of Psilocybe cubensis, the most widely grown psilocybin mushroom. It is a cultivar name used by growers and shops, not a species, and nothing about its origin is documented in a primary source. No laboratory has published a measurement of its psilocybin content. This issue collects what can be verified and marks what cannot.
Contents
6 papers ยท updated 10 October 2026
| No. | Paper and abstract | Reading | Sources |
|---|---|---|---|
| 01 | What McKennaii is: a cultivar name, not a species McKennaii is a growers' name for a line of Psilocybe cubensis. How the species is defined, what the cultivar label means, and what genome data show. | Reading 4 min | Sources 7 |
| 02 | Where the name McKennaii comes from What is documented about the McKennaii name: the McKenna brothers, their 1971 Amazon trip and grower's guide, and the two unverified origin stories. | Reading 3 min | Sources 4 |
| 03 | What lab studies say about differences between cubensis strains Measured psilocybin and psilocin in named Psilocybe cubensis strains, variation between single mushrooms and flushes, and why McKennaii has no lab data. | Reading 4 min | Sources 7 |
| 04 | McKennaii effects: what is known, and what is not No study describes effects specific to McKennaii. What is documented about psilocybin mushrooms in general: onset, duration, risks and dangerous combinations. | Reading 2 min | Sources 4 |
| 05 | Growing McKennaii from a kit, and recognising contamination What a McKennaii grow kit contains, what the shop's instructions say, why the cultivar needs no special care, and how to recognise mould and bacteria. | Reading 3 min | Sources 5 |
| 06 | Is McKennaii legal? Mushrooms and grow kits by country Legal status of McKennaii mushrooms and grow kits in the Netherlands, the United Kingdom, Germany and the United States, with dates and primary sources. | Reading 4 min | Sources 12 |
Notes to the reader
Key findings
- Name. The ending "-ii" imitates the Latin form botanists use to honour a person, here the writer Terence McKenna (1946 to 2000). There is no evidence that he or his brother Dennis named, selected or distributed the strain. See the history paper.
- Identity. A sample sold as McKennaii was grown from spores and whole-genome sequenced in 2021; the raw data are public in the US National Center for Biotechnology Information archive. A 2023 genome study of 86 commercial cultivars found that most descend from related populations and share identical versions of the psilocybin genes. See what McKennaii is.
- Strength. Studies that measured named cubensis strains under one method found differences of more than sevenfold between strains, and 13 to 23% variation between single mushrooms of the same strain. McKennaii was not among the strains tested. See strain differences.
- Effects. No study describes effects specific to McKennaii. What is known applies to psilocybin mushrooms in general. See effects and safety.
- Law. In the Netherlands, grow kits may be sold, but psilocybin mushrooms have been banned since 1 December 2008. In the United Kingdom, Germany and under United States federal law the mushrooms are controlled as well. See legal status.
How to read this site
Each page is written as a short paper: an abstract first, numbered sections, tables with captions, and a numbered reference list at the end. Superscript numbers in the text point to that list. Where a claim rests on a shop's own description or on a magazine interview, the text says so.
The growing page is short on purpose. It covers what differs for McKennaii kits and how to recognise contamination, and refers to the shop's manual for the rest. The site is information for adults; it does not recommend using or growing anything where that is illegal.