Lophophora

Lophophora is a genus of four accepted species, erected by John Merle Coulter in 1894 from the basionym Echinocactus williamsii Lemaire on the basis of unarmed areoles, a fleshy taproot, and limestone-substrate specialization. All members are spineless, button-shaped cacti native to northeastern Mexico and a narrow strip of southern Texas, with woolly areole hairs in place of spines and a taproot that typically exceeds the above-ground stem in mass.

Lophophora williamsii occupies a crescent-shaped range from the limestone scrub of Webb, Starr, and Zapata counties in south Texas, south through Coahuila, Nuevo León, Tamaulipas, San Luis Potosí, and Querétaro, at elevations of 100 to 1,900 m. It grows beneath nurse shrubs in gravelly, alkaline soils where rainfall averages 200 to 600 mm per year. Lophophora diffusa has a much smaller range confined to Querétaro and Hidalgo in central Mexico.

Kew’s Plants of the World Online currently accepts four species: L. williamsii, L. diffusa, L. fricii, and L. alberto-vojtechii. Many AI overviews and older references cite only two species, omitting the more recently accepted taxa. Numerous named varieties and forms, including crested (f. cristata) mutations, are recognized by growers but carry no formal taxonomic standing.

The clearest visual clue is stem colour and rib structure: L. williamsii has blue-green to grey-green stems with 4 to 13 distinct ribs and furrows, while L. diffusa shows yellowish-green stems with a flattened or warty surface and no defined ribs. They also differ chemically: L. williamsii carries mescaline as its dominant alkaloid, whereas L. diffusa’s primary alkaloid is pellotine. Geographic origin provides a third check, since any wild-type specimen from outside Querétaro and Hidalgo states is almost certainly L. williamsii.

Lophophora produces diurnal flowers from May through September, with peak flowering during the summer monsoon period. The flowers are funnelform, 1 to 2.4 cm long, typically pinkish-white with a deeper pink midstripe, and last two to three days each. Seed grown plants in cultivation can reach flowering size in as few as 3 to 5 years under optimal conditions, compared with 10 to 15 years for wild specimens.

All four Lophophora species face habitat pressure from agricultural conversion, livestock grazing, and illegal collection. The IUCN Red List classifies L. williamsii as Vulnerable with a declining population trend; per-species assessments for L. diffusa, L. fricii, and L. alberto-vojtechii are summarised on each species page. The genus is listed under CITES Appendix II, requiring documentation for all international trade. In Mexico, NOM-059-SEMARNAT-2010 lists the native populations as protected, prohibiting wild collection without federal permits.

Cultivation legality varies by species and jurisdiction. The genus is listed under CITES Appendix II, requiring documentation for international trade in live plants and seed. Mexican law (NOM-059-SEMARNAT-2010) protects all native populations, and wild collection requires federal permits. Nursery-propagated seed of all four species is legally available across the European Union, the United Kingdom, Canada, and Australia. Lophophora williamsii is regulated separately in some jurisdictions; see the Lophophora williamsii species page for country-specific guidance.

Lophophora performs best in a sharply draining mix of 50 to 60% pumice or lava rock blended with decomposed granite or limestone chip to replicate its native limestone-scrub soils. Water thoroughly during the active growing season (spring through early autumn), allowing the substrate to dry completely between waterings, then keep plants nearly dry from late October through February. Full sun or very bright indirect light encourages compact growth and reliable flowering.