Quaqua pruinosa grows many branches from near the base of the single main stem. They are decumbent or somewhat erect and hairless, attenuating or tapering slightly to their tips. The long, narrow stems vary in colour among grey-green, dark green, purple and nearly black on plants in habitat. Stems of up to 50 cm long have been recorded.
The stems are four-angled with bulging, rounded, longitudinal stem ridges. These ridges are covered in single rows of about equally spaced, small tubercular teeth that are hard and brown at their tips. The ridges meet in vertical (longitudinal) seams or grooves that are deep and narrow.
The plant in picture has a solitary flower near the tip of its main stem (Frandsen, 2017; White and Sloane, 1973; iNaturalist).