Etymology - From the Greek word for ashes -tephra referring to the ash-colored stems.Tephrocactus is a small genus in the subfamily Opuntioideae which is endemic to Argentina. Like other members of this group, Tephrocactus does have glochids, however, they are uniquely sunken into the areoles in this genus. Spines may be long, dense and needle-like or thin and papery or absent. The stems grow in very distinct segments, but unlike the flat-pads found on the genus Opuntia, the segments of Tephrocactus are round. This can be either in short cylinders, egg shaped, or even spherical. Thes segments typically grow in a slightly zig-zagged stack. Flowers are white in most species or pinkish, sometimes yellow, and in one case red.
Some species in this genus are very popular in cultivation. Grown for their alien-looking stems and dramatic spines. Flowers are less common in cultivation as the segments often detach with the slightest touch. Plants that are only a couple segments high tend not to flower. As such, a flowering Tephrocactus is a special delight to the hobbyist.