This bizarre variant of Gymnocalycium mihanovichii, the common South American cactus, is known for being completely spineless and crested.  These will tolerate more water but can be more sensitive to cold.  This particular plant has been cultivated by Thai growers under partial shade— if you increase the amount of light over time they may form spines!

Care

Gymnocalycium will take a little more water than most other cacti but can go with little to no water during the winter. Protect from freezes by covering or bringing inside.

Photographed in a 2.75” pot