Crassula tetragona coloured by December sun

Crassula tetragona gets its specific name of tetragona from the leaf arrangement on the stems, botanically called its phyllotaxis. Plants with opposite leaf pairs succeeding each other in a perpendicular manner like those of C. tetragona are said to have decussate phyllotaxis.

The leaves of the species are also quite variable: cylindrical or sometimes flat, always succulent. They may be from 1 cm to 5 cm long, usually incurved and up to 5 mm in diameter, tapering to sharpish tips. Leaf colour may be grey, green or pinkish red as in this photo taken near Touwsrivier (Vlok and Schutte-Vlok, 2015; iNaturalist; Wikipedia).