Origin and Habitat: Lophocereus schottii is native to the desert regions of mainland Mexico in the states of Baja California, Baja California Sur, Sinaloa and Sonora. Small populations also occur in the extreme south of Arizona. The monstrous form is restricted to a small area NE of El Arco, about halfway down the Baja peninsula.
Altitude range: It grows from sea level to 800 m asl.
Habitat: It tends to grow in colonies in favourable locations in dunes, stream shores, thin soil and on rocky hillsides. It grows mainly on alluvial plains in dry gravely soils and in desert riparian environments, but its northern limit in southern California can get frosts that can occur on the flat sites where it grows. Here plants are smaller in size than their more southerly counterparts. Reproduction in this part of its range is predominantly asexual and occurs either by the dispersal of stems in the immediate vicinity of parents, or by the long-distance transport of detached stem pieces downstream by floodwaters. Wild plants are heavily weathered and badly marked with just the newest growing tips in good condition. In Arizona and Sonora it occurs in desert scrub. The northern distribution is limited by freezing temperatures The species is abundant, in some places exceedingly so, and widely distributed. The population is generally stable, although perhaps declining on the continent (not on islands or peninsula). Land transformation for agriculture (mainly on the continent, and parts of the peninsula), and resort development along the coast are the main threats affecting this cactus.
Ecology: Lophocereus schottii schottii has recently been found to have an obligate mutualistic association with a pyralid moth, Upiga virescens, which pollinates the small flowers and lays its eggs in them so that the larvae can develop by feeding on the fruit tissues. Females of this moth collect pollen on specialized abdominal scales and actively deposit pollen on the stigmas of sinita flowers. As much as 90% of the fruit set may be due to these moths. Patrolling ants attracted to extrafioral nectaries in the ar-eoles may provide protection from herbivorous insects. Birds and ants remove the pulp and seeds, leaving only the hollowed fruit case.