Where the name McKennaii comes from

Terence and Dennis McKenna

Terence McKenna was born on 16 November 1946 in Paonia, Colorado, and died on 3 April 2000 in San Rafael, California (Wikipedia: Terence McKenna¹). He became known for lectures and books on psychedelic plants and fungi. His younger brother Dennis McKenna trained as an ethnopharmacologist and later worked as a researcher.

In early 1971 the brothers travelled to La Chorrera in the Colombian Amazon, looking for a plant preparation used in the region. There they found fields of P. cubensis. In a retrospective written fifty years later, Dennis McKenna describes how they collected spores of these mushrooms and took them home, and how it took them "a couple of years" before they found a simple way to grow small amounts on sterilised rye grain in jars (Dennis McKenna, 2021²).

The grower's guide

The method became a short book, Psilocybin: Magic Mushroom Grower's Guide, published by And/Or Press in Berkeley under the pseudonyms O.T. Oss and O.N. Oeric. Dennis McKenna dates it to 1975; other sources, including the Wikipedia biography, give 1976. A revised edition followed in 1986, by which time more than 100,000 copies had been sold, according to the same biography.

Table 1. Dated events connected with the name.

The book matters for this story because it made home growing of cubensis accessible to a wide public. It does not, as far as we could establish, describe or name a culture called McKennaii.

Two origin stories

DoubleBlind magazine summarises the two versions that are repeated online (DoubleBlind³):

1. The strain was developed from a spore print found in Terence McKenna's collection after his death in 2000.
2. A cultivator in the Netherlands developed the strain and named it in McKenna's honour, or for marketing.

The same article quotes the mycologist Caine Barlow, a co-author of a 2023 genome study of commercial cultivars, as saying that genome sequencing supports the second version. We have not seen that comparison in published data. Neither story names a person, a date or a collection, and we found no statement from the McKenna family about the strain. Both are best read as unconfirmed.

What the "-ii" ending says

The ending looks Latin on purpose. Botanists and mycologists form names that honour a person with a Latin genitive ending. The current International Code of Nomenclature for algae, fungi, and plants sets out how: for a man's name ending in a consonant, "-ii" is added (its example is lecardii for Lecard); for a name ending in "-a", the ending is "-e" (trianae for Triana) (ICN, Article 60⁴). A species named after McKenna under those rules would end in mckennae.

That detail is a small clue that the name came from the growing hobby and not from a formal description. Nobody published a type specimen or a diagnosis, and the code does not apply to trade names. The Latin look gives the name an air of taxonomy that it does not have, which is also why it is sometimes misread as a species; see what McKennaii is.

What remains unknown

• who first named a culture McKennaii, and in which year;
• whether all cultures sold under the name today descend from that first culture;
• whether the culture came from material connected with the McKenna brothers at all.

If a reliable first-hand source turns up, this page will be updated. Meanwhile, the measurable questions are covered in strain differences.