Strombocactus disciformis is a rare species of cacti and the only species of the genus Strombocactus. The plant originates from Central and Northeast Mexico.
Strombocactus is a monotypic genus with a strong turnip-like root, a small, depressed, roughly spherical stem covered with spirally arranged overlapping tubercles, each with a spine-bearing areole at its tip.
Strombocactus disciformis are low-growing, gray-green succulents with a broadly round, unbranched stem and root. In their natural habitats, they grow in a disk shape, half hidden in the ground, reaching around 8 cm in diameter and 2-3 cm in height. In cultivation, they become nearly spherical. Adult tubers can reach 15 cm in diameter, larger than the above-ground parts. The plant's spiral ribs are deeply notched, creating a wart-like appearance with a ratio close to the golden ratio (13:8). Areoles are located on the blunt ends of these warts, which are curved (straighter in cultivation) and have a square base. They rarely have more than four or five short, bristly thorns, which fall off after a few years.[1]
Flowers come from new growth at the crown, emerging from the youngest areoles. The flowers, white to cream or magenta and 2.5 to 3.5 cm long and open to about 4 cm in diameter. The 7 mm long, thin-walled brown fruits contain 0.3 mm reddish-brown seeds.[2]
The species has two recognized subspecies:[3]
| Image | Subspecies | Distribution |
|---|---|---|
| Strombocactus disciformis subsp. disciformis | Querétaro to Hidalgo | |
| Strombocactus disciformis subsp. esperanzae | Guanajuato | |
Strombocactus disciformis is found in the Mexican states of Querétaro, Hidalgo, and Guanajuato, growing on almost vertical, weathered limestone rocks at altitudes of 1000 to 1600 meters.[4]
First described as Mammillaria disciformis by Augustin-Pyrame de Candolle in 1828, the specific epithet disciformis is derived from the Latin "discus" (disc) and "-formis" (shaped), referring to the plant's shape.[5] Nathaniel Lord Britton and Joseph Nelson Rose reclassified it as Strombocactus in 1922.[6]
Both subspecies are classified as Vulnerable on the IUCN Red List, which states that it has a limited range and "is experiencing a decline in mature individuals due to illegal overcollection". The species is listed in Appendix 1 of the Convention on International Trade in Endangered Species meaning commercial international trade is prohibited and non-commercial international trade is regulated.