Notocactus herteri

Notocactus (Parodia) herteri is South American species from Uruguay. It is a larger plant, growing as a ball to a size of 6 inches or more and only after that slowly turning to a column.
Tho plants I have, grown from the same bag of seeds, have much different flower color. The plant at picture has flowers dark pink, and the other produces much lighter pink, almost lavender blooms. Both plants bloom freely and reliably, but only once during the season, in mid-summer.