The dull green, three-foliolate leaves of Aspalathus setacea are variable, consisting of linear or nearly cylindrical, needle-like leaflets that are straight or slightly curved and sometimes grey- to silver-haired, otherwise hairless. The ascending leaflets mostly end in tiny spine-tips.
The specific name, setacea, is derived from the Latin word seta meaning a bristle, referring to the spine-tipped leaflets.
Leaflet length is from 13 mm to 18 mm, the width about 0,3 mm (Euston-Brown and Kruger, 2023; Bond and Goldblatt, 1984; iNaturalist; https://www.worldfloraonline.org).