Gorteria diffusa is a winter-growing annual, typically reaching heights of 50 to 300 mm. Its growth habit is sprawling from the base, characterized by a slender taproot and numerous fibrous lateral roots. The stems are cylindrical, diffusely branched, hairy and often purplish. The leaves are variable, linear, lanceolate or oblanceolate and arranged alternately, measuring 20 to 50 mm in length and 5 to 8 mm in width. The leaves taper below. They are bright green, with a hairy upper surface and a woolly lower surface, and the margins are typically entire but sometimes toothed or pinnatifid, and revolute. The capitula are radiate, solitary, sessile, and terminal, with diameters ranging from 20 to 35 mm. The involucre is ovoid, with acuminate, sharply pointed bracts that are hairy toward the tips, united at the base into an urn-shaped cup. The involucre encloses the fruits after flowering. The ray florets are ligulate and sterile, the ligules measuring 12 to 20 mm in length and 4 to 6 mm in width, narrowed at the base. The ligules are orange above and dull purplish below, typically featuring a dark basal, glossy spot on one to all of the florets, each with a small white reflective dot. The 5-lobed disc florets are orange, with outer florets mostly female-fertile, and inner florets male. The anthers are shortly sagittate at the base, with an ovate apical appendage. The style is subglobose at the base, with linear-lanceolate branches. The cypselas are obovoid, silky towards the tip. The pappus consists of minute scales hidden among the cypsela hairs. The cypselas germinate within the closed involucre (Duncan & Ellis 2011). Flowering time is from midwinter to spring, July to October, with a peak in August and September.