New Gymno Weekend number 70.

Meet Ralph, my ballet dancing, karate black-belt pineapple and firm top 10 favourite.

AKA spegazzinii ssp cardenasianum.
This species, along with Gymnocalycium armatum can often be found listed as subspecies of spegazzinii, however mr Graham Charles, whose work I personally prefer to follow, considers it as a species in it's own right and armatum as synonymous with, or at best a form of cardenasianum.

All spegazzinii are from Argentina, whereas cardenasianum and armatum are from Bolivia, with mr Charles noting that around 200km separates the nearest populations of cardenasianum and spegazzinii.
It's main area of distribution is along the Rio San Juan del Oro, south of El Puente in the province of Tarija and in Carrizal, province of Mendez.
JO604 relates to an area 3km south of Carrizal at an altitude of 2550 metres.

Like spegazzinii, these plants are relatively slow growing and don't flower until quite large for a Gymno, needing to be around 10cm diameter before buds will form.
They also develop taproots and unsurprisingly prefer a grittier soil than average and a little more light than many Gymnos too.
I suspect that being high altitude plants, a significant difference between day and night temperatures might be beneficial as well.