Etymology -The name is derived from the Greek erion, meaning wool and sykon meaning fig, referring to the wooly fruits.Eriosyce is a group of mostly globose or somewhat cylindrical South American species. Their round ribbed stems, which in most species are heavily armed with dense strong spines, and similar flower structure had earned them a place in the genus Echinocactus in early taxonomies. However, the genus has existed since Rudolph Philippi in 1872 and everyone for the last 100 years or more agrees these plants are not Echinocactus. Despite this, the default listing here of Eriosyce includes species that are considered unique even today. The two primary names still used today are Neoporteria and Neochilenia with a third name of Islaya being used as a monotypic genus of one species. All three of these names are still commonly found on tags in cactus grower’s collections as well as in the cactus nursery trade.
Many species have been given both the name Neochilenia and Neoporteria at some time in the past. However, modern growers distinguish them in this way: Neochilenia have short to no spines and funnel shaped flowers that enable the inner part of the flower to be clearly seen when fully open. The floral tubes of Neochilenia are hairy and these later form hollow, fleshy fruits. In contrast, species in the Neoporteria group have denser, longer spines in general than Neochilenia. The flowers are bright pink with yellow interiors and are more of a tube shape as the inner petals remain mostly closed. The outer petals flare out and thus, the flower is not truly a tube shape as other cactus genera, but even when fully open, the inner parts of the flowers are still obscured by petals. The floral tubes may have a little fuzz and form similar fruits to the Neochilenia group. The plants considered Islaya are highly variable and cover a large range in Chile and Peru.
In total, plants in the genus Eriosyce are rugged survivors of arid South American deserts. Many occur at high altitudes where they endure big temperature swings and high UV. To deal with the harsh climate, the plants will sit dormant until conditions are again favorable. This environmentally controlled growth leads to a big discrepancy between plants in habitat and those in cultivation even of the same species. Plants in cultivations with sparse spines and plump round stems may be flattened and covered with spines so dense that the stem is not visible at all. This variation, as well as the differences described above, has led to an enormous amount of synonymous names being published.