(Förster) H.Friedrich & Glaetzle
Trichocereus bridgesii Britton & Rose
Echinopsis lageniformis is a fast-growing columnar cactus from the high deserts of Bolivia. The species is also known by the earlier binomial Trichocereus bridgesii. Although some botanists have tried to merge the entire Trichocereus genus with Echinopsis they have met with varied success among experts over the past thirty years. This is an ongoing vigorous dispute between groups of scientists commonly known as "lumpers" and "splitters", depending on each individual's ideas of what constitutes sufficient grounds for renaming a plant or moving it into a different genus. These differences are primarily concerned with microscopic examination of the reproductive structures inside each flower of the plants in question. The differences are rarely visible to the naked eye, and no easy solution is in sight to the dilemma of lumpers vs. splitters. Among the indigenous populations of Bolivia, it is sometimes called achuma or wachuma, although these names are also applied to related species such as Echinopsis pachanoi which are also used for their psychedelic effects.
The plant is of light green colour and usually has 4 to 8 ribs. It can grow 2–5 m tall with stems of up to 15–20 cm in diameter. Spines are honey-coloured to brown and are located on the nodes in groups of up to 4. They can grow up to 6–7 cm in length and in fully grown plants are spaced evenly on the ribs, 2.5 to 3 cm apart.
As with related species, it seems to have long shamanic tradition of use throughout its homeland. Chemical analysis of some variants of this species have shown it may include some of the most potent of the psychedelic Trichocereus species, although this is not conclusive nor does it apply to all strains of the species. Outside of its native habitat, it is one of the least known and used of the Trichocereus cacti for either its psychoactive or ornamental uses. This is not true in areas where it is the dominant species, for example, the La Paz area of Bolivia.
There exist several mutant varieties of this species that are highly prized by ornamental cactus collectors. These include a cristate variety, two variants of monstrose growth, and a more recently developed clone that exhibits both monstrose and cristate growth. Of the monstrose varieties, one is often known by the name Penis Plant. These all tend to be much slower growing than the standard form of the species, but owing to their highly unusual shapes, they are sought after by cactus collectors.