Psilocybe guilartensis is the most commonly-found hallucinogenic mushroom in Puerto Rico, yet only recently described by science in 1997. It is suspected to contain both psilocybin and psilocin, though the potency is currently undetermined. While occasionally found in the Dominican Republic, this Caribbean species is primarily restricted to the US Territory.
This species shares many similarities with some other Psilocybe members, though they do not share the same range; P. cinnamomea is found only in China, while P. moseri is rarely found outside of Mexico. P. portoricensis and P. caerulescens are found in the same range, though they display different identifiable characteristics.
P. guilartensis is most easily recognized by its dark, violet-brown cap. A strong bluing reaction to damage or handling can make this a very dark mushroom, especially with age. A second defining feature is the characteristic yellow fibres or bristles found near the base of the stipe, a rarity among the Psilocybe genus.
A further differentiating feature of P. guilartensis is its flavour and scent, both mildly reminiscent of mustard or horseradish, though layered with the starchy flavour common to Psilocybe species. Other commonalities include the translucent-striations on its bell-shaped cap, which flattens with age and occasionally has an umbo.
While P. guilartensis is common in Puerto Rico, it still retains preferences for its habitat. The mushrooms, with tall, slender, hollow stipes, are most likely found in disturbed habitats in tropical or subtropical forests. They grow directly on clay or moss and are recognized visitors to hiking trails, coffee plantations and in the remains of landslides.
Though having a limited range, and little availability of spores online, amateurs in Puerto Rico are likely familiar with this species. A confirmed hallucinogen, the potency of fresh and wild samples is unknown but likely to pack a punch, so proceed with caution if found on your next vacation.
Guzmán G, Tapia F, Nieves-Rivera ÁM, Betancourt C. (1997). Two new bluing species of Psilocybe from Puerto Rico. Mycotaxon 63(1): 377-382.
Guzmán G, Tapia F, Ramírez-Guillén F, Baroni TJ, Lodge DJ, Cantrell SA, Nieves-Rivera ÁM. (2003). A new species of Psilocybe in the Caribbean with an emendation of Psilocybe guilartensis. Mycologia 95(6): 1171–1180.