A sclerotium (plural sclerotia) is a compact mass of hardened fungal mycelium that holds nutrient reserves. Many unrelated fungi form them as survival bodies: a 2025 review describes sclerotia of one soil fungus that can stay viable for decades (Wang et al., 2025). The word names a structure, not a group of species.
A few Psilocybe species form them. The 1978 paper that named Psilocybe tampanensis says sclerotia had then been reported for three species, P. mexicana, P. caerulescens and P. tampanensis (Guzmán and Pollock, 1978). In 1959 Albert Hofmann and colleagues reported psilocybin and psilocin in fruit bodies, lab-grown mycelium and sclerotia alike (Hofmann et al., 1959).
They are called “magic truffles”, but a true truffle is an underground fruiting body that spreads spores (Kennedy et al., 2026); a sclerotium is not. They became famous in the Netherlands, where a Dutch minister said in 2011 that they fall outside the Opium Act (Dutch government answer, 2011). Canada has no such gap: the Controlled Drugs and Substances Act covers any substance containing psilocybin or psilocin.
Sources
- Wang et al., 2025, Frontiers in Microbiology
- Guzmán and Pollock, 1978, Mycotaxon (PDF)
- Hofmann et al., 1959, Helvetica Chimica Acta
- Controlled Drugs and Substances Act (Justice Laws)
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