Strombocactus (2012)

By Eric Driskill (April 2012)

Strombocactus is in the family Cactaceae. The plants are found in Queretaro, Mexico, which is at the same latitude as Guadalajara and Puerto Vallarta. Queretaro is located in north-central Mexico south of San Luis Potoso. The state is one of the smallest in Mexico, yet is one of the most heterogeneous geographically, hosting ecosystems from deserts to tropical rainforests.

Queretaro is divided into five regions. One of these, the Sierra Gorda, is in the north and is part of the Sierra Madre Oriental. The topography is rugged with high elevations and steep valleys. It is a conjunction of mountains and hills formed mostly of limestone, with wide contrasts in climates and vegetation.

Strombocactus plants have the most distinct habitat – high on limestone cliffs at 3,300 to 5,300 feet elevation. Even though the plants often grow in inhospitable, virtually inaccessible locations, they have been severely threatened by illegal collection.

Augustin Pyramus de Candolle described Strombocactus in 1828 as Mammillaria disciformis, with little other location information than Mexico. In 1922, Nathaniel Britton and Joseph Rose described the genus Strombocactus for the single species, with the type locality as Mineral del Monte, Hidalgo, Mexico. Rose had collected material of the plant in the state of Queretaro in 1905.

The name strombocactus derives from the Greek word “strombos,” meaning fir cone or spinning top, referring to the shape of the plants, and the Latin word “cactus.” Disciformis derives from the Latin adjective “disciformis,” which means disk-shaped, circular, flat. At times, there has been speculation as to the similarity of Strombocactus and Aztekium. Sue Skillman and Edward Anderson published a 1984 study of the two genera and concluded they should remain distinct.

Strombocactus plants are small, solitary and occasionally many stemmed. The stems are flattened to semiglobose – often with depressed, woolly centers — up to 5 inches high and 3.5 inches in diameter. The plants are absent of ribs and have one to four spines. Their flowers are pink or cream. Some believe the genus has just one species: disciformis, with a few subspecies, and others argue that the genus has two species: disciformis and pulcherrimus.

The strombocactus is often regarded as a choice and difficult plant. In cultivation, it is relatively easy to grow, as long as you aren’t in a hurry to go from seedlings to large specimens, as the plants are very slow-growing. Like many other slow-growing species, you often see them grafted – more for the impatience of the hobbyist than the difficulty of cultivation. Plants grown hard with good light will likely retain the natural compact, flat shape and not become elongated and unnatural in appearance.

With the plants growing at such a slow rate, one may be tempted to purchase a larger, possibly field-collected specimen. I highly recommend that you find a nursery man who has plants available from seed, which may be smaller, but you can rest assured that these endangered plants remain in the wild and thrive in our hobby.